The Proceedings of the 18th Annual Conference of China Electrotechnical Society

Electric vehicle (EV) charging safety risk factors are numerous and complex, and using fault trees can explore the key possible causes of EV charging faults. However, the traditional fault tree analysis method to solve the minimum cut set is quite complicated and lengthy. Based on the binary decision diagram (BDD), the fault tree can be solved across the cut set, and the minimum cut set can be obtained directly by traversing the BDD, which can achieve fast analysis of faults. However, the sorting of the basic events seriously affects the structure of the BDD and directly impacts the spatial and temporal complexity of the BDD. In this paper, the appropriate sorting rule for EV charging risk analysis is proposed and combined with the if-then-else algorithm to convert the fault tree into an optimal structure of BDD, which can quickly complete the analysis of the EV charging fault tree. The results show that the method proposed in this paper can reduce the number of nodes of the BDD.

The physical and chemical properties of epoxy resin cured products prepared with different types of toughening agents show significant differences. In order to study the influence of molecular structure of different toughening agents on the electrical properties of cured epoxy resin, three kinds of epoxy polymers were prepared by the reaction of three commonly used toughening agents dibutyl phthalate (DBP), polypropylenglycol diglycidyl ether (PPGDGE), and phenol-formaldehyde resin F-51 with E-51 epoxy resin. The results show that when the toughening agent is 10wt% PPGDGE, the impact strength of the epoxy polymer is the highest, at 28.02 kJ/m2, which is 41.2% higher than that of unmodified epoxy resin. Based on Materials Studio, the free fraction volume and root mean square displacement of the cured molecules of these three different structures of epoxy resin were analyzed. The study found that when 10wt% PPGDGE was used as the toughening agent, the free volume proportion and mean square displacement displacement of the material were minimized. The simulation results showed that the toughening effect of epoxy resin was PPGDGE > F-51 > DBP, which is consistent with the experimental results.

In this study, 10wt % of methyl methacrylate-butadiene-styrene (MBS) copolymer was introduced into PLA, and the heat resistance of the material was improved by annealing. The MBS/PLA mixture before and after annealing was comprehensively characterized by mechanical test, scanning electron microscope, thermal deformation temperature test, X-ray diffractometer, FTIR spectrometer and high voltage breakdown test. The mechanical test results show that MBS, as an effective toughening agent, can improve the notched impact strength of PLA materials from 17.34 kJ/m2 to 74.34 kJ/m2. The heat deformation temperature test shows that annealing treatment can improve the heat resistance of MBS/PLA mixture by 30.55 ℃. X-ray diffraction pattern shows that annealing treatment can improve the crystallization degree of MBS/PLA mixture. The power frequency breakdown voltage test shows that the addition of MBS only reduces the breakdown voltage of PLA by 12.34%, which means that the introduction of MBS does not significantly weaken the insulation performance of PLA, so it will not significantly affect its application potential in power equipment.

With the rapid development of DC power transmission engineering, epoxy matrix composites with high dielectric strength have broad application prospects in power systems. Based on the negative electron affinity of nano-diamond, the electrical properties of epoxy resin composites after aging were studied. After drying, the epoxy resin composite (EP) and the epoxy composite (EP/NDs) with 4phr nano-diamond were placed in a high temperature aging chamber and sampled every two days to determine their macro properties. The study found that compared with EP/NDs, the breakdown voltage increased by 10.25% after aging, the volume resistivity decreased by two orders of magnitude, and it was more stable. Through molecular dynamics simulation analysis, it is found that the Fermi level of diamond is higher than that of epoxy resin matrix. Due to the difference in energy level, the high-energy electrons in diamond tend to move to the resin matrix with lower energy level, resulting in negative charge on the diamond surface, which changes the migration of electrons in the material and improves the breakdown performance.

Energy storage is an effective solution to bridge renewable energy and industrial energy demand by alleviating their intermittency problems. Thermochemical energy storage (TCES) is a more efficient energy storage method in this application compared with sensible heat storage (STES) and latent heat storage (LTES), as energy is stored in strong chemical bonds via a reversible chemical reaction so that it can offer higher energy density with less energy loss during long-term storage and long-distance transport, due to the temperature-independent storage of the working pairs. In this report, the state-of-the-art thermochemical energy technologies are reviewed and discussed, especially for medium temperature applications (200–500℃), including material selection.

Based on hydrogen fuel cell operating principle, the coupling relationship between Nernst voltage, activation overpotential, ohm overpotential, concentration overpotential and gas input parameters, bipolar plate flow characteristic, reaction temperature were analyzed with voltage calculation as the main line. Then the calculation method of hydrogen fuel cell performance under Multi-physical fields is described. According to the voltage calculation process, a Simulink simulation module was built to calculate the battery output characteristics under the influence of multi-parameter correlation. The example shows that the collector plate quality has an important effect on battery reliability and the battery performance can be improved by increasing the hydrogen and oxygen pressure and reaction temperature. The research is of great significance for the optimal design of hydrogen fuel cells.

The simulation of icing on fan blades primarily involves three processes: water droplet collision, capturing, and freezing. The calculation of local collision coefficient of water droplets is of utmost importance. This article presents a simulation calculation model for the flow field of a fan blade airfoil based on the boundary element method. It derives a criterion for water droplet collision on the blade surface and achieves rapid tracking and collision assessment of water droplet trajectories. Furthermore, a method is proposed to calculate the local collision coefficient of water droplets based on the collision velocity of water droplets and the normal vector of the blade boundary. Based on this methodology, simulation calculations were conducted to determine the collision coefficients of water droplets on both clean and icing fan blades. The results of these calculations were compared with those obtained using the finite element method. The findings indicate that the calculation method for the local collision coefficient of water droplets on fan blades, based on the boundary element method outlined in this paper, exhibits high accuracy and can be employed for the rapid calculation of water droplet collision coefficients in the simulation process of fan blade icing.

Four different neural networks and regression algorithms are applied to the power prediction of fuel cell vehicles. The prediction results of the four different power prediction algorithms are compared using historical vehicle data. The effects of the number of nodes in the hidden layer and the parameters of the algorithm on the prediction results are investigated. Then, the relevant parameters are optimized. After the comparison, the long short-term memory algorithm (LSTM) was finally selected to be applied to the whole vehicle model, and a moving horizon algorithm was embedded to generate the moving horizon long and short-term memory algorithm (MH-LSTM). The number of hidden layer neurons, prediction time scale and moving pane scale affecting the model performance of this power prediction algorithm are analyzed and optimized. The simulation results verify that the strategy can achieve adaptive regulation of the fuel cell output power under NEDC conditions and the charge/discharge balance of the battery charge state.

Optical measurement based on optical principles has unique advantages in terms of anti-interference and sensitivity, making it an important method for partial discharge detection. This paper proposes an abnormal discharge detection technology for power equipment based on a light-guiding structure, which consists of the light-guiding structure and a silicon photonic semiconductor-based spectral sensing system. The light-guiding structure can be placed inside the power equipment to sense the localized discharge optical signals and transmit them to the spectral sensing system outside the equipment for abnormal discharge detection. Optical simulation methods are used to analyze the optical path of the light-guiding structure, and a partial discharge test platform is built to verify the effectiveness of this abnormal discharge detection technology in enlarging the detection range of partial discharge and achieving multi-spectral detection of partial discharge. This provides a new approach for online monitoring of internal partial discharge in enclosed power equipment.

The magnitude of motor vibration and noise is an important indicator to evaluate the performance of the motor. In this paper, taking a double-stator single-rotor axial permanent magnet motor as an example, the electromagnetic force wave order distribution of the motor is obtained by magnetic potential magnetic conductivity method, and the axial air gap magnetic density and electromagnetic force wave of the motor are analyzed by means of two-dimensional Fourier decomposition. Secondly, a joint simulation model was established, and the vibration and noise of the motor was analyzed by the finite element method and the vibration and noise tests were carried out on the prototype, which verified the correctness of the analysis. Finally, the structure of the motor was optimized, the amplitude of the electromagnetic force wave of the motor was reduced, thereby reducing the vibration noise of the motor.

The article verifies a sensorless control strategy for current source inverter (CSI)-driven permanent magnet synchronous motor (PMSM) using a high-order sliding mode observer (SMO), specifically applicable in the medium to high speed range. The CSI, known for its motor-friendly output waveform with low dv/dt, addresses the issue of motor terminal overvoltage under long cable conditions. PMSMs, characterized by their high power density, have garnered attention in the field of long-line operations, with expectations of replacing induction motors. However, their drive requires rotor position information for decoupling torque and excitation components. This article validates the feasibility and superiority of using a high-order SMO to improve position observation convergence speed and reduce steady-state error in the sensorless control of CSI-fed PMSM drive system. Simulation of the control system for CSI-fed PMSM drive supports the proposed methods.

For the imbalanced distribution of photovoltaic component-level fault data samples, which are easily affected by environmental and internal factors, a machine learning-based multi-fault diagnosis strategy for photovoltaic string level is proposed. Firstly, the data of different fault states of photovoltaic components are cleaned, filtered, and the original fault features and higher-order fault features (RD, relative deviation) are constructed. Secondly, the prediction performance of three mainstream models, namely decision tree model (LightGBM), linear model (LR), and deep model (MLP) is compared, indicating that the performance of the decision tree model (LightGBM) is significantly better than the comparative models. Finally, the important features are using the SHAP technique, and the risk factors related to different fault types are analyzed from both the group and individual perspectives. The results show that the RD feature can effectively improve the performance of different models, with a 10% increase in AUC when comparing LightGBM models with and without RD. The decision tree model (LightGBM) is determined to be more suitable for diagnosing photovoltaic faults, with an AUC value of 0.939. The application of the SHAP technique provides more diversified explanations, analyzes the importance of data features for different fault types in both group and individual settings, and visualizes them, which will help provide decision references for on-site operation and maintenance personnel in fault analysis and handling.

The important thermophysical properties related to thermal chemical energy release of Ca(OH)2 and Mg(OH)2 found in the literature have been summarised. These properties include specific heat capacity, energy density, reaction enthalpy, chemical equilibrium, and reaction kinetics. Based on these property values, it can be observed that both hydroxides are suitable for medium-temperature thermal storage applications, with their optimal thermal chemical reaction temperatures falling within the range studied. Furthermore, both hydroxides exhibit high energy density and favorable reaction kinetics for dehydration and hydration reactions.

This paper, through the infrared precise temperature measurement special electric live detection carried out during the electricity consumption peak of winter season in the substation under the jurisdiction of a power supply company, found that the temperature of the B-phase arrester on the 35 kV side of a 110 kV main substation was abnormal and the leakage current was much higher than those of the other two phases. After power outage, electrical test was conducted. Through disassembly inspection, it was found that the surface of the aluminum strutting piece in the phase arrester was oxidized and there was obvious traces of water and other abnormalities. After disassembly of the abnormal valve piece, pressurization and infrared temperature measurement test were carried out which found at least 6 pieces of the 13 pieces valve piece in the arrester were deteriorated. Through the electric field simulation, it was found that if there is a gap, it will generate an impact on the electric field at the entrance of the lug of the arrester but does not affect the overall electric potential distribution of the arrester. While through the electric - temperature field simulation, it was found that under normal circumstances, the overall temperature distribution of the arrester is more uniform; the temperature distribution of the arrester under moisture is not uniform in which case the resistivity of the faulty valve piece is reduced. Its temperature is lower than the normal valve piece, and the overall resistance of the arrester would be reduced, thus driving an increase in current and temperature.

Based on the related characteristics of hydro, solar and wind multi-energy power generation in Beipanjiang River basin, this paper has investigated the optimal configuration of diverse energy storage modes. The basic idea is to use pumped hydro-storage system to adjust the regulation of hydro-power stations while hybrid energy storage combining electric-chemical and hydrogen storage to optimize the configuration of photovoltaic power stations over the region of Beipanjiang River Basin. Under the objective minimizing the cost with the constraints of energy storage system capacity and the maximum value of the charge/discharge power, the economic benefits of different types of energy storage device have been analyzes before the optimal hybrid energy storage configuration bing resolved. The optimal configuration scheme of the energy storage capacity for multi power generation systems are discussed with the practical data which may provide a valuable solution for this region in real practice.

Aiming at the problems of the traditional methods in the field of parameter identification of permanent magnet synchronous motor (PMSM), it is difficult to identify multiple parameters at the same time and the identification accuracy is not high enough, this paper proposes a Multi-link improvement Harris Hawks Optimization (MIHHO) .Firstly, Logistic chaotic mapping is introduced from the initialization direction of the population to initialize the position of the eagle group, increase the diversity of the population, and accelerate the convergence speed of the algorithm in the early stage. Secondly, from the perspective of the position update of the eagle, the random reverse learning strategy is used to optimize the worst position individual in the eagle, so as to improve the fuzziness and randomness of the algorithm, enhance the global search performance and accelerate the convergence of the algorithm. Finally, in order to prevent premature convergence, the best individuals of this iteration are retained to enter the next iteration to improve the problem that the traditional intelligent algorithm is prone to local optimization and precision decline. On the basis of the mathematical model based on the PMSM voltage equation, the PMSM parameter identification model is built on the simulation platform to test the MIHHO and the standard Harris Hawks Optimization (HHO), particle swarm optimization (PSO) and Sparrow search algorithm (SSA).The simulation results show that MIHHO has better stability, convergence speed and higher identification accuracy for PMSM parameter identification.

To study the effect of temperature on the space charge characteristics of epoxy composites for HVDC GIL, epoxy/alumina micro-composites (EP-AL) and epoxy/silica micro-composites (EP-SI) were selected for comparative study, and their space charge behavior and trap characteristics were analyzed at different temperatures. The results indicate that the space charge distribution of the epoxy composite exhibits significant temperature characteristics. Higher temperature will increase the charge injection at both electrodes and the trapping rate inside the material, thereby increasing the overall number of charge carriers. Through horizontal comparison, it is found that EP-AL is more likely to accumulate homopolar charges compared to EP-SI. At 80 ℃, the dissociation effect of impurities inside the EP-AL is greatly enhanced, and the phenomenon of heteropolar charge accumulation is more obvious, reducing the charge accumulation of the sample. The insulation performance of EP-AL at high temperature is better than that of EP-SI. Due to the fewer deep traps in EP-SI, the mobility of charge carriers significantly increases, and at the same capture rate, the migration depth of charge carriers is deeper, resulting in more severe distortion of internal electric field.

The submerged phase change cooling technology has excellent heat transfer performance, can reduce the ground occupation of the ice melting device, and has good economic benefits. The application of immersion phase change cooling technology to the converter valve of the ice melting device will make the valve section in the complex environment of gas-liquid two-phase state, and it is necessary to carry out insulation test on the valve section in the two-phase flow state. This paper provides the method of reliable and stable generation of two-phase flow, summarizes the insulation test items that need to be carried out in the valve section of two-phase flow, and provides the criterion of passing the insulation test.

Using electromagnetic force to directly accelerate projectiles to hypervelocity, railguns can be applied in the military field. The characteristics of existing Pulse Forming Network (PFN) based on energy-storage capacitors as Pulsed Power Supply (PPS) driving railguns are analyzed, which has such shortcomings as low system efficiency and low firing rate. A kind of PPS model for multi-stage parallel LCR square-wave circuits is proposed based on such theories as Fourier series principle, LCR attenuation oscillation circuit characteristics, and Kirchhoff’s current law. The matching relationship among such parameters as capacitance, inductance, and resistance of multi-stage parallel LCR square-wave circuits has been designed according to theoretical analysis. Taking a 10-ms pulse width and 2.4-MA amplitude as an example, a five stage parallel LCR square-wave circuit is designed to drive railguns with the sliding contact resistance RR = 0.5 mΩ and the load inductance LR = 4 μH. Then the above scheme is calculated using Matlab software, and the results show that the fluctuation rate of current amplitude is less than 10%, and about 64% of the total electric energy is residual and can be fully recovered in the capacitors after one round. The above new PPS work driving electromagnetic railguns with high firing rate and high firing efficiency is of great significance for promoting the military application of electromagnetic rail gun technology.

In order to solve the morphological awareness needs of overhead transmission line, a 3D reconstruction algorithm of composite overhead transmission line shape embedded three intervals of 120° nonorthogonal FBG array was proposed, which has temperature self-compensation characteristics. The overhead transmission line form 3D reconstruction process was elaborated in detail, the model of transmission line based on FBG was established and the three-dimensional coordinate expression of the trajectory line was derived. Combined with the finite element model, the simulation comparison experiments were carried out, and the trajectory and sag of 200 m span transmission line with equal height and unequal height at both ends were analyzed under the conditions of self-weight and icing. The trajectory line morphology obtained from the morphology perception algorithm proposed in the article is basically consistent with finite element model simulation, with a maximum sag error of no more than 4.5%. It has high reconstruction accuracy and can be used for the perception of three-dimensional morphology and sag of overhead transmission lines.

An accelerated calorimeter (ARC) was used to accurately measure the total heat production of the battery under high rate discharge, calculate the heat production of the battery by the simplified Bernadi equation, calculate the irreversible heat of the battery by the potential method and the internal resistance method respectively, calculate the reversible heat by measuring the entropy heat coefficient, sum the irreversible heat and the reversible heat measured by different methods and compare them with the total heat production respectively, and conclude that under high magnification discharge using potential method is more accurate for heat generation estimation, and proposes a more accurate method for heat generation prediction of batteries in engineering, and provides a basis for battery assembly. Moreover, the experimental results indicate that under high-rate discharge (30C), the trend of the battery’s internal resistance with ambient temperature remains essentially the same as that observed during low-rate discharge (below 1C).

At Xuefeng mountain natural icing test base, this paper carried out icing flashover tests on composite post insulators with different pollution levels. According to the photos taken by high-speed camera, the AC discharge process of post insulators and the development law of arc speed and arc length are studied. The test results show that, 1) AC discharge process is clearly divided into unstable and stable development stages, the stable development stage is divided into slow development stage and critical flashover stage. 2) there are two phenomena: arc levitation and arc bridging. Arc levitation will lengthen the arc and arc bridging will shorten the arc length(L). Floating arc and short circuit are two ways of arc deformation. 3) There is a critical arc length(Lc) during the arc development, which is between 62.6%*H and 64.6%*H. 4) Significant differences exist in different discharge stages for arc velocity(Varc). When it is less than Lc, Varc is less than 4.8 m/s. When Lc is reached, Varc increases sharply, and Varc can reach 70.67 m/s or above. The research results could contribute to providing useful reference for the external insulation design and anti-icing flashover design of transmission lines with icing area.

At Xuefeng mountain test base, this paper carried out the icing flashover tests for insulators (4 types) with different pollution degrees and icing weights. The influence of salt deposit density (SDD), icing weight(W) and icing stress product (ISP) on AC icing flashover voltage of insulators is analyzed. The research result show that, 1) The flashover voltage decreases with the increase of SDD, and flashover voltage and SDD is a negative exponent power function; 2) Flashover voltage decreases gradually with the increase of W, and flashover voltage and W can well meet the exponential function relationship; 3) Both SDD and ice weight reduce the electrical strength of insulators, and SDD has little influence on the characteristic index m of W. The effects of SDD and W on the flashover voltage are independent of each other. That is, for iced insulators, ice can be considered as a special form of pollution; 4) The flashover voltage of long insulator strings is a power function with ISP. The flashover voltage decreases with the increase of ISP and finally tends to be saturated.

With the development of pulsed power technology, the high voltage large current discharge pulse power supply needs more and more energy, which used for the high frequency repetitive discharging, so that the primary energy should be with high power and high accuracy. The High-frequency high-voltage capacitor charging power supply (CCPS) is widely used as the primary energy in the field of pulsed power because of its simple structure, mature technology and high stability, but restrict by the power density and charging speed, it has not widely used in the high frequency repetitive large current discharging. In order to enhance the out power, there are 15 CCPS are parallel connected at the output end, which are unified controlled by the upper computer software, so that the 15 CCPS can finish the rapid charging for the large capacitor load. At the same time, the voltage feedback and timing function of the upper computer software are used to control the repetitive charging frequency of the 15 CCPS, so that the charging precision and charging rate can be controlled accurately.

The PM has many advantages such as high output torque, high efficiency and low noise. However, it is possible to observe the slot effect, resulting in noise and vibration, which will influence the precision of the machine. To reduce the cogging torque of PM motor, a 24-slot 4-pole electrical machine was used as an example. First, we use a method of energy to analyze the generation mechanism of the cogging torque, and then choose the best parameters, including pole arc, air gap, pole offset, PM thickness, and slot hole width. Lastly, we select the most important parameters to optimize. After matching the appropriate mathematics model, we apply the mixed GA to search for the limitation of the model. On the basis of the simulated results of the FEM analysis of the engine model with an optimal solution, the cogging moment of the motor can be decreased by 82.16%, the efficiency improved by 1.6 percent and the torque pulse decreased by 8.2%.

The transformer is particularly important for the safe and reliable operation of State Grid, and different damped form has a significant impact on the state of the transformer. The results show that the real part of the frequency domain spectroscopy(FDS) of single-layer and double-layer dry or damped oil-immersed pressboard decrease with increasing applied voltage at the same test frequency point , and the value of the dielectric loss curve increases with increasing applied voltage at the same test frequency point, while the value of both the real part and dielectric loss curve increases with increasing applied voltage at the same test frequency point for the partially damped samples.

In the context of China's carbon peaking and carbon neutrality goals, the future will witness a gradual increase in the proportion of renewable energy consumption. Large power users, characterized by high electricity demand and carbon emissions, play a crucial role in both the electricity market and the carbon trading market. Therefore, studying the market trading demand, strategies, and risks for these users within the framework of carbon-electricity market and demand response (i.e., clean energy consumption) is of significant importance. This research focuses on large power users in the steel industry and screens the key factors influencing power and carbon trading. The study also analyzes the coupling mechanism between the carbon and electricity markets. Based on this analysis, a system dynamic trading model is developed, taking into account renewable energy quota constraints, policy constraints, economic benefits, environmental values, and other factors. The model simulates the participation of large users in both the power market and the carbon market. The results indicate that, under renewable energy planning, an increase in the consumption ratio leads to higher power purchase costs for large users and an overall increase in the cost of carbon-electricity coupling market trading. However, the impact on trading risk is minimal. These comprehensive analysis results provide valuable insights for designing carbon-electricity coupling market trading models for large power users under renewable energy consumption policies.

This paper proposes an improved method based on the Gipps model for predicting electric vehicle (EV) charging load to address the spatiotemporal uncertainty and randomness of electric vehicle charging load. Firstly, using the Markov process to simulate the spatial transfer characteristics of electric vehicles, and combining it with trip chaining theory to describe the travel patterns of electric vehicles. Secondly, the Dijkstra algorithm plans vehicle travel routes to get the distance of each journey segment. The log-normal probability distribution functions are fitted to estimate the dwell time, and a spatiotemporal distribution model for daily vehicle travel is established. Then, based on the improved Gipps and taking into account the influence of road class, temperature and other factors on the electricity consumption of EVs, micro traffic analysis is carried out on the driving process of vehicles. Finally, the EV charging load is input to the corresponding 33-node distribution network, and the sequential power flow algorithm is used to evaluate the impact of EV charging on the distribution network. The results show the correctness and feasibility of the proposed model.

In view of an abnormal event of dissolved gas in 220 kV transformer oil, it is inspected and analyzed from all kinds of aspects, such as data comparison between online and offline oil chromatography monitoring, absolute gas production rate analysis, and Pentagon analysis method, to find out the cause of the fault. The accuracy of David Pentagon analysis method is verified.

Partial discharge (PD) is one of the most important indicators for high voltage power transformer diagnostics. For better detection, one has to know the PD propagation characteristics along transformer windings. This paper utilizes the multi-conductor line theory to establish the winding model for 750 kV transformer. With this model, PD occurrence at a specific winding location is simulated. The derived result can be used to improve the PD detection accuracy for high voltage power transformers.

Small sealed electromagnetic relay is a type of commonly used micro switching devices in the aerospace field. Efficient thermal analysis methods are required in the design and analysis process. For finite element method (FEM) for relay temperature simulation has a complex boundary setting and takes long time to build model and solve. When handling multi-dimensional calculations, FEM has a low adaptability to design processes of a complex systems. This article provides a design method from the perspective of matrix transformation - inverse thermal path model - temperature rise calculation - scheme comparison - product implementation. Based on the principle of thermal circuit, a thermal circuit basic unit was established, and its thermal network was abstractly established for a typical 1/2 crystal case sealed electromagnetic relay; Build an experimental system for testing, compare the experimental data with the calculated data of the thermal network model, and verify the correctness of the thermal network model. Based on the topology analysis method, the thermal circuit topology model of the electromagnetic relay was analyzed. Searching for reasonable potential thermal paths in relay design and proposing optimization solutions. Based on the optimization scheme, the topology model of the thermal path matrix is inverted back into the thermal path, and the temperature rise of different optimization design schemes is calculated using a heat transfer equation set. Applying this method to the aforementioned typical 1/2 crystal case sealed electromagnetic relay, multiple optimization design schemes for the product were quickly obtained, and the product optimization design was completed, greatly improving the efficiency of thermal analysis and design.

Partial discharge (PD) detection and location is crucial for power transformer diagnostics. Normally, the location is determined by solving space-based equations with multiple detected PD signals. This method demands for synchronized measurement which is usually realized by sophisticated wiring. This paper proposes a new method to locate the PD by non-synchronized signals with the help of digital twin model. A finite element method (FEM) model for ultrasonic PD signal propagation is established for a specific transformer, which serves as the digital twin. By comparing the results from this digital twin and the measured signals, PD can be located. Example is shown for a 750 kV transformer. The simulation result validates the proposed approach.

In DC transmission system, we must make the insulation design of converter transformer reliable, which is very important for the safe operation of transmission system. At present, the research on the space electric field of the oil-paper insulation structure is limited to the simple and equivalent flat electrode model, and there is a lack of research on the electric field characteristics of large-scale complex structures. In this paper, the internal electric field of the valve-side outlet model is measured and compared with the simulation results, and the distribution characteristics of the electric field and electric charge in different oil gaps are obtained. The experimental results show that: under AC voltage, the difference between the measured electric field and the simulated value in the inner oil gap is 1.73%. Under DC voltage, the electric field in the inner oil gap is 30.1% larger than the value in the middle oil gap and increase first and then stabilizes with time. The electric field in the middle oil gap is 51.3% larger than the value in the outer oil gap and increase first and then decrease with time and finally stabilize. The space electric field in the oil changes significantly, and there is a charge concentration on the oil- pressboard interface. By testing the space electric field in the oil under AC and DC voltages on the device based on the electric field equivalent model, the variation law of the space electric field has been obtained.

Nowadays, the converter transformer has become one of the key equipment in the High voltage direct current (HVDC) transmission system. Due to factors such as the interface charge in the insulation structure of the oil-pressboard, the internal electric field is uncertain. Considering that the internal structure of the transformer is relatively complicated, it is necessary to perform non-contact measurement of the uneven electric field and interface charge of the oil-pressboard composite insulation structure under DC voltage. In this paper, based on the Kerr effect, a liquid dielectric photoelectric field measurement platform is established. By actually measuring the electric field in oil and calculating the charge on interface between oil and pressboard, the distribution characteristics of the electric field and the interface charge can be obtained under the condition that the DC electric field is non-uniform. The experimental results show that as the pressurization time increases, the space electric field has a decaying trend, and the interface charge has an upward trend. The electric field decay and charge accumulation are more obvious under negative voltage. As the measurement position under the upper electrode deviates from the center more and more, the spacial electric field in oil becomes smaller and smaller, but the accumulated charge on the oil-pressboard interface shows an upward trend.

Research on isolated micro-grid is of great significance in solving problems such as remote areas or islands and urban power supply, which can effectively alleviate the increasingly severe electricity shortage problem. To meet the load demand of the micro-grid, an isolated micro-grid system consisting of photovoltaic, wind, diesel, battery, and a three-objective optimization model considering system comprehensive economic cost (CEC), load power shortage probability (LPSP), and pollutant gas missions (PGE) is established. An island was taken as an example to optimize the configuration of the microgrid, and the reliability of the proposed three-objective model was verified. The feasibility of the Improved NSGA-II algorithm (INSGA-II) is verified by comparing with the NSGA-II algorithm. Three representative solution and one compromise solution are selected through simulation. The results showed that INSGA-II achieved a 3.7% reduction in CEC and a 13.5% reduction in PGS, respectively. The isolated micro-grid system model can be applicable to areas with similar climate and conditions.

As a key component of high-voltage DC transmission, the insulation failure rate of the converter transformer has remained high. The main insulation of the converter transformer is oil-paper composite insulation structure, its insulation performance is jointly determined by transformer oil and high-density transformer pressboard. Therefore, it is necessary to study the evolution of the electrical characteristics of oil and paper insulation under different working conditions in different aging conditions. This paper studied the partial discharge (PD) inception voltage (PDIV) characteristics and Breakdown characteristics of three transformer oil-impregnated pressboard after aging at a high temperature of 90 ℃ for 1 day, 7 days, 21 days, 28 days and 35 days. And we obtained the evolution law of the dielectric constant and resistance characteristics of the three oil-impregnated pressboards under long-term operating conditions, and compared the three transformer oils from different parameter perspectives, which could provide a basis and reference for the selection of insulating oils for converter transformers.

In order to effectively improve the efficiency of GIS equipment condition maintenance, it is necessary to accurately evaluate its health status, and it is important to select the effective state quantity. This paper analyzes the historical data of defects and faults of GIS equipment, and quantitatively evaluates the detection effectiveness of related status quantities of GIS equipment from the method of defect detection. The results show that the defect detection rate of monitoring alarm is the highest, and the detection effectiveness of frequent suppression, oil leakage, body gas chamber leakage and corresponding state quantity of secondary accessories of the mechanism is the best among the monitoring alarm defect detection methods. Among the detection methods of live detection defects, the effectiveness of the corresponding state of bulk partial discharge and gas chamber leakage was the best. Among the abnormal events of existing equipment, insulation defects such as air leakage and partial discharge of the body and mechanical performance defects of the mechanism and box accounted for the highest proportion. In the operation and maintenance of the equipment, the ultra-high frequency and ultrasonic partial discharge detection, body temperature rise, abnormal noise, SF6 density meter and pressure gauge corresponding to the above defects should be strengthened. The research results have reference significance for the reliable operation and maintenance of GIS equipment.

According to the secondary Frequency modulation (FM) scheme of energy grid, the integrated control strategy of battery energy storage is proposed, and the adaptability of various battery is evaluated to improve the economy of energy grid. Firstly, the secondary FM model of battery energy-conventional unit participating in the energy grid is constructed to solve the problem of slow frequency response of conventional unit. The energy storage (ES) is then split into two components with distinct charging and discharging properties for fusion, extending the battery's useful life. Finally, through the evaluation of battery life and operating cost, the optimal battery selection under different ES operating modes was obtained.

With the rapid development of high-voltage transmission engineering technology, oil-immersed paper (OIP) capacitor bushings, as one of the main components in the transmission system, are facing unprecedented challenges for the composite insulation reliability. At present, the optimization designing of bushing insulation performance is mainly focusing on the new material and structure. However, there are few reports on the application of nano-modified technology for the transformer bushing. In this paper, the oil-immersed paper modified by nano-TiO2 particles with different mass fractions were prepared, relative permittivity of samples was measured at various temperatures, and electro-thermal coupling model of OIP capacitor bushing was established. The experimental results show that nanoparticles can reduce the relative permittivity of the samples, and the using of oil-impregnated paper modified by nanoparticles can reduce the electric field strength outside the bushing core and the electric field strength variance of the bushing.

Triggered vacuum switch are widely used in power systems and the field of pulsed power. Their reliable triggering and current carrying capacity are mainly affected by the macro characteristics of vacuum arcs, among which the volt ampere characteristics of vacuum arcs are an important indicator reflecting the breaking performance of switches. In order to measure the volt-ampere characteristics of vacuum arc, a set of arc test device based on triggered vacuum switch with multi-rod electrode is designed in this paper. The device consists of a main circuit and a triggering circuit, where the main circuit analogs pulse working condition and the triggering circuit provides initial plasma. The feasibility and effectiveness of the circuit design scheme were verified through simulation and experiments. The triggering conduction of the vacuum trigger switch was tested, and the switch voltage and circuit current were collected. The experimental results verified the positive volt ampere characteristics of the vacuum arc. The research work provides theoretical support for the design and the performance improvement of vacuum switch.

Nano-TiO2 is used to improve the electrical properties of oil-paper due to its small size and large specific surface area. However, due to the characteristics of the operating conditions for the oil-paper composite insulation system, the temperature differences always exist between the internal and external surface of the oil-paper structure, and the mechanism effect of nano-TiO2 on the space charge distribution characteristics for the oil-paper under the different temperature differences is not yet clear. Therefore, the space charge and electric field distribution characteristics for the modified and unmodified samples under different temperature differences are studied by pulsed electro-acoustic method. The experimental results show that the accumulation of charges is observed inside the samples at low temperature difference, but the unmodified one is more obvious. With the increasing of the temperature differences between the internal and the outside the cellulose insulation pressboards, the accumulation of hetero charges on the anode side causes the electric field to distort for the samples, but the electric field distortion rate of the pressboard modified by nano-TiO2 is less than that of the unmodified one. As a result of the addition of nano-TiO2, the oil-paper's field strength distribution is improved due to the reduction in space charge accumulation.

When power grid personnel perform outdoor operations, the physiological function of people in high temperature environments will be abnormal or changed, and in serious cases, it will lead to heat stroke, if not timely rescue, it is more likely to lead to sudden death. In order to reduce the harm of high temperature environment to outdoor power grid operators, a new type of water cycle cooling clothing is designed, which adds automatic temperature control system and semiconductor refrigeration on the basis of traditional water cycle cooling clothing. The cooling coat uses PID algorithm combined with PWM modulation of single chip microcomputer. STC89C52 single chip microcomputer is used as the control core of the cooling coat. PID algorithm is combined with power electronics technology to achieve different cooling effects by controlling the flow rate of the pump. The experimental research shows that the designed cooling clothing has a cooling time of about 100 min, and the temperature difference with the environment can reach 12 ℃, which has a good cooling effect.

With the continuous advancement of the dual-carbon target, the rapid development of distributed small-capacity photovoltaics takes a challenge to the expansion of distribution network capacity. According to the problem of high penetration of distributed photovoltaic access to distribution network, an overall optimization method of microgrid cluster structure is proposed. According to the planning and operation characteristics of microgrid based on distributed photovoltaic, a microgrid cluster structure analysis model is established. Considering the randomness of photovoltaics, the interaction between microgrids, energy conversion, interaction, and the operation of microgrid clusters, the objective function of microgrid cluster optimization is constructed. A transformer location algorithm based on Voronoi diagram is proposed, which can realize the overall capacity optimization after the microgrid group is integrating into the distribution network. The distributed photovoltaic access distribution network in a certain area was taken as an example, the simulation calculation is carried out. The calculation results show that the microgrid cluster structure can improve the photovoltaic absorption capacity and operation efficiency, optimize the increase of distribution network capacity, and reduce the cost of distribution network planning.

Phase change cooling system is a key component of high power electronic equipment, and its insulation performance plays a very important role in the stable operation of power system. Aiming at the problem of two-phase flow charging in the phase change cooling system, a device for generating and detecting two-phase flow charging is designed in this paper, and a test method for two-phase flow and single-phase flow charging is proposed. First of all, it can generate two-phase flow, control the two-phase flow in a certain boiling state to measure the flush current, simulate the actual condition of phase change media in high-power power electronic equipment. Secondly, it can measure the charging of single-phase liquid flow at the same time and compare the charging degree of the same phase change medium in the two-phase state and the monomeric state. Finally, the specific operation process of charging the two-phase flow and single-phase flow is given.

The energy systems in an AC-DC hybrid system containing wind power have the potential to trigger faults in each other. These faults can excite faults in other parts of the system. Based on the characteristics of chain faults, four related indicators are calculated: link prediction indicator, weighted tidal entropy indicator, AC/DC line coupling indicator, and wind power access ratio short-circuit ratio indicator, and the corresponding comprehensive weights are obtained by using the improved hierarchical analysis method and the comprehensive assignment method. Subsequently, the improved IEEE39-node wind power AC/DC hybrid grid is used as a simulation model for the study of chain faults, and the initial disconnected fault lines are determined and then the chain fault sequences are obtained by comparing the values of comprehensive indexes to the fault lines at all levels, and the simulation results verify that the method is effective.

In the context of ‘‘dual carbon’’, with the rapid development of urban construction, the requirements for power supply reliability and power quality have become very stringent, and it is urgent to improve the rapid response ability to deal with distribution network failures. In this paper, the minimum line loss limitation strategy and the transmission line ampacity limitation strategy are adopted. In the case of multiple transfer paths, factors such as line loss and load rate among different transfer schemes are preprocessed to select the optimal transfer path. For the path to transfer. And the feasibility of the strategy is verified by ring network simulation.

The contact state of the contact is related to the stable operation of the power system. In order to study the contact state changes during contact operation, this paper establishes a contact resistance measurement method based on pulse current, and selects plummer contacts as the research object to obtain the contact resistance changes under changing contact pressure and applying vibration. The research results show that compared with the normal contact state, the contact resistance of bad contacts is more likely to be affected by current changes and vibration, which leads to local overheating.

With the development of wide variable frequency AC power supply system, the PFC(Power Factor Correction) function of aero equipment is more difficult for realization in the digital control system, especially harmonic disturbance included in the input voltage. A digital control strategy is proposed, with the application of the variable sampling/switching frequency. In this scheme, the sampling/switching frequency is set as a fixed proportion to the input voltage frequency in order to adapt the frequency variety. In addition, a repetitive controller for harmonic suppression is introduced, which can significantly improve the performance of the current control. Simulation results in Matlab validate the effectiveness of the proposed strategy.

The armature-rail contact resistance is generally considered to reflect the contact state of the armature and the rail during the launch process of the electromagnetic railgun. However, due to the extremely short time of the armature acceleration process, it is difficult to directly measure the armature-rail contact resistance. In this paper, based on the simplified muzzle voltage model of the electromagnetic railgun, a numerical calculation method of contact resistance is proposed, which considers the armature body resistance and current skin effect, based on the experimental current, muzzle voltage waveform and combined with finite element simulation and MATLAB Program to perform calculations. Comparing the calculated results with the ratio of muzzle voltage to current (muzzle resistance), it is found that the value of the muzzle resistance is 2 to 3 times that of the calculated contact resistance.

For the hermetically sealed electromagnetic relay (HSER) and other load-sensitive electromagnetic components, combined with the high-performance, low-density characteristics of nano-microcrystalline magnetic materials, the introduction of wavelet principal element analysis method, to get the dynamic characteristics of the strong correlation of the high-frequency principal element components of the time-domain distribution, which is used to optimize the design of the target-looking characteristics. Combined with the lightweight requirements of the small-looking characteristics, the electromagnetic finite element-dynamics model two-way coupling simulation as a calculation basis, using Monte Carlo-based Taguchi method to design the replacement scheme and dynamic characteristics, quality comparison, parameter optimization, and finally get the core replacement-based optimization design scheme, and the actual fabrication of nano-microcrystalline magnets HSER, to build a test system, prototype test results proved that the optimization The prototype test results proved the effectiveness of the optimized design method, and the HSER prototype realized the weight reduction of the electromagnetic system while ensuring the improvement of the dynamic characteristics.

At present, in the field of marine engineering, the demand for the application of pulse loads is increasing day by day, and the common ones are: high-frequency radar, ice-breaking device and high-power electromagnetic system. Due to the high energy and short period characteristics of pulse loads, the input of pulse loads will impact the stability of ship integrated power system. To address this issue, this paper carries out simulation modeling for common ship integrated power system, and based on the simulation comparison of two different common types of pulse power load waveforms, discusses the impact of the sag control on the stability of the system under different circumstances. The results show that the larger the slope of the pulse power curve, the larger the impact on the system. At the same time, the use of sag control can effectively realize power distribution for the generating unit and improve the stability of the system, but the sag control also affects the generator output and leads to the fluctuation of bus voltage. And the impact on the system stability caused by the input of impulse loads with too high energy still needs to be buffered by external energy storage devices. These conclusions also provide a reference for subsequent studies.

Metal oxide varistor (MOV) is widely used to protect power equipment from overvoltage impact in substation. The MOV can be degraded during the operation and it is important to monitor its status. Resistive current is calculated from leakage current and has much higher sensitivity to evaluate the status of MOV. However, there are some inevitable interferences which influence the calculation accuracy of resistive current. The phase-to-phase interference is one of these influence factors and induced by the coupled capacity of adjacent MOVs, which makes the phase position of leakage current lagging or leading the real phaser. This phenomenon can make the calculation of resistive current much smaller or larger than the real value, which should be corrected. In this work, a simplified decoupling method was proposed to remove the phase-to-phase interference to leakage current induced by adjacent MOVs. Field experiments were conducted in a 500 kV substation. The proposed method was verified by applying to the field data and comparing with measurements with other monitoring devices.

Most magnet power supplies of Lanzhou heavy ion accelerators cooling storage ring are switch mode power supplies, operating in the mode of high pulsed current and high-precision. There are a large number of capacitors with various levels. The reliable operation of capacitors is very crucial for the reliability and stability of power supply. Based on the impedance frequency characteristics of capacitor and the FFT algorithm, this study extracts capacitor voltage and current at specific frequencies, enabling online monitoring of ESR and capacitance values. A 400 V, 10000 μF electrolytic capacitor is taken as an example to evaluate the ESR on different current conditions, and the ESR parameter of the capacitor is measured by an LCR meter. The error between the monitoring results and the measurement results is within 5%, which verifies the effectiveness of the method. The proposed method is also applicable to thin film capacitor, which helps to improve the reliability of capacitor operation and achieve efficient and predictable maintenance.

The matching design of C-type solid armature affects the efficiency of electromagnetic launch. The elastic theory utilized in the past to analyze the initial contact state between the armature and the rails has a phenomenon where the nominal contact area is much larger than the actual contact area, which affects the analysis of mechanical contact characteristics between the armature and the track. In this paper, we adopt the normalized design idea of C-typed armature, compare the structural parameters of C-typed armature with electromagnetic launch caliber, obtain the parameters of head coefficient, throat coefficient, tail length coefficient, tail thickness coefficient, overfilling coefficient, and use the elastic-plastic model to analyze the influence of each coefficient on contact pressure, contact length and contact starting position during the loading process of C-type armature, and get the head coefficient (H_ head = 0.48), throat coefficient (H_throat = 0.45), tail length coefficient (L_tail = 1.3), tail thickness coefficient (H_tail = 0.14), interference coefficient (H_inter = 0.06), the best coefficient values of the coefficient parameter model for simulation The analysis and comparative experimental study, the test results show that the structural parameter coefficient of this armature improves the average kinetic energy of armature firing by 12.6% compared with other coefficient parameters. The effectiveness and practicality of the armature firing efficiency under this coefficient condition are proved, which provides a standard design method for the design of C-typed armatures.

This article proposes a homopolar inductor alternator with a permanent magnet that can move radially outward. The motor has lower no-load electromagnetic losses under idle operating conditions, which can effectively increase the efficiency of the flywheel energy storage system. This article introduces the structure of this motor and analyzes the operating principle of this motor. As the distance between permanent magnet and motor stator is different, the magnetic field strength in the main magnetic circuit of motor is different, and the magnetic field of motor can be adjusted by adjusting the radial displacement of permanent magnet. Finally, the theoretical calculation results were verified using finite element simulation. The simulation results show that the proposed mechanical magnetic induction motor has very low no-load iron loss under idle operating conditions.

Mechanical defects in the travel of three-position switches not in place are an important factor in the failure of GIS equipment and a serious threat to grid security. In order to realise the effective operation and maintenance of mechanical defects in three-position switch travel, this paper builds a simulation platform for mechanical defects in travel using real three-position switches, studies the vibration law of the three-position switch breaking and closing action process under normal and energy resistance defects, and carries out a comparative analysis of the vibration characteristics and vibration parameters of three-position switches in different states with multiple measurement points in the time/frequency domain. The results show that: the vibration signal amplitude is related to the distance between the location of the measurement point and the location where the defect occurs; the normal three-position switch operates smoothly and has weak vibration amplitude and light pulses, while the impact tooth effect caused by the energy resistance defect produces a cyclic shock vibration signal with stronger vibration amplitude and longer transient action time; the absolute mean value of vibration in the time domain and the energy value in the frequency domain of the three-position switch defect are significantly greater than the normal state, based on which the qualitative determination of the presence or absence of defects can be effectively achieved.

The problem of low control accuracy is common in the new energy power system, especially with the increase of the installed capacity of wind turbines and the increase in the number of controlled wind turbines, the higher requirements for the whole field control strategy, the more obvious the problem of low control accuracy. In response to the above problems,, after analyzing the two fundamental reasons for the large control error of wind turbine group, Firstly, this paper optimizes the closed-loop control of the entire wind farm by using the improved PID (Proportion Integration Differentiation) controller, and eliminates the error caused by line loss. Secondly, aiming at the problem of large error caused by obvious oscillation in the small power section in the wind turbine group control process, the sliding step theory is proposed, and in the process of small power section control, the wind turbines with the least amount of intelligent allocation participates in the control, thereby reducing the oscillation and error, and finally, the actual open-loop and closed-loop control data of multiple wind turbine group are analyzed. The actual field results show that after using the algorithm in this paper, the whole field control accuracy of the wind turbine group can reach within 1%, which effectively solves the problem of low control accuracy of the whole field of the large-capacity wind turbine group, The frequency stability of wind farm grid connection has been improved step-by-step.

The photovoltaic centralized inverter is the core component of the photovoltaic power generation system, and its health status is critical to the output power quality. In PV inverter failures, more than half of the faults occur on the bus capacitor, and its capacity drop will increase the harmonic output, and the complete failure state will cause the power generation system to stop. The causes that affect the capacitor life are overvoltage, harmonic current, high temperature, etc. The inverter fault caused by the degradation of capacitor performance causes the operation of the photovoltaic power generation system to be interrupted, and the replacement and maintenance of the faulty module brings time and power generation benefit loss. Temperature is the main factor affecting the life of the capacitor, the temperature rise of the bus capacitor is mainly affected by the ripple current flowing through, the operating state of the inverter unit of the photovoltaic power generation system is changed with the uncontrollable photovoltaic input and AC bus bar, the temperature rise of the capacitor under different operating conditions, and the voltage and current output change of the capacitor capacitance under the same conditions, etc., analyze the relationship between the temperature rise of the capacitor and the operation and the relationship between the inverter output characteristics of the capacitance change, and provide theoretical support for the identification of the capacitor health state.

Research on the coordinated control of sub-microgrids in multi-microgrid systems is limited, with issues such as large overshoot and slow response speed in control methods. Firstly, the virtual synchronous motor (VSM) technology is introduced into the sub-microgrid layer, proposing a coordinated control strategy for multi-microgrids under different power exchange scenarios, enabling stable operation of the system during grid connection/disconnection and changing operational scenarios. Secondly, fuzzy PI control and improved particle swarm optimization algorithm are introduced to enhance the effectiveness of coordinated control based on traditional VSG control. Finally, through case studies, it is demonstrated that the proposed coordinated control scheme based on VSG effectively suppresses frequency and voltage fluctuations in multi-microgrid systems under different power exchange scenarios. A comparison is made among three control methods, and experiments conducted on a multi-microgrid system testbed validate that the improved VSM-based coordinated control scheme exhibits faster response, smaller error, and more stable output.

Aiming at the shortcomings of electrolytic capacitors such as large size, short life and poor environmental adaptability, resulting in low power density and poor system reliability, this paper proposes an active capacitor that can be applied to high-power occasions. Traditional active capacitors can often only be used in small and medium-power occasions, and the active capacitors designed in this paper can use the theory of difference frequency reactive power to convert high-frequency power into low-frequency power and improve the utilization rate of active capacitors, so as to realize the replacement of electrolytic capacitors by active capacitors in high-power systems. In order to verify the reliability of the difference frequency reactive power theory, this paper designs an active capacitor topology based on the difference frequency reactive power theory, and builds a MATLAB/Simulink experimental simulation platform, and the simulation results show that the active capacitor can compensate for the inherent double frequency fluctuation of the inverter in a high-power system.

This paper presents a comprehensive study on the moisture characteristics of oil-paper insulated transformer bushings using frequency domain dielectric spectroscopy. The dielectric response properties of oil-paper insulation models subjected to uniform and non-uniform moisture conditions are analyzed based on the principles of frequency domain spectroscopy. Furthermore, research efforts are carried out to investigate the diagnosis and practical application of field oil-paper insulated bushings using dielectric spectroscopy tests. A novel assessment method is proposed to evaluate the moisture uniformity in oil-paper insulation equipment, considering the distinct dielectric response characteristics associated with uniform and non-uniform moisture distribution. Specifically, non-uniform moisture distribution leads to prominent loss peaks and fluctuations in the curves. The proposed theoretical model is validated through frequency domain dielectric spectroscopy tests and physical and chemical analysis of disintegrated transformer bushings. The study provides a reliable approach for on-site moisture assessment of transformer bushings, thereby enhancing the accuracy of insulation health diagnosis in the presence of non-uniform moisture conditions.

Digital Twin (DT) is the core technology of intelligent manufacturing in the future, and is an important enabling means to achieve the deep integration of digital economy and real economy. This paper takes PCB coreless axial flux permanent magnet synchronous motor (PCB motor) as the research object, and realizes the digital mapping of PCB physical entity motor by establishing high-precision electromagnetic thermal analysis model, so as to realize the estimation of key variables. In terms of electromagnetic model, this paper establishes the analytical model, magnetic flux model and loss calculation model, reflecting the three-dimensional magnetic field characteristics of PCB motor. The thermal twin model of PCB motor is built based on the thermal network to realize the thermal characteristics of the model mapping, which can realize the real-time calculation of the temperature. Finally, the twin visual interface of the motor is constructed based on Unity3D, and the collection, upload and storage of motor operating information is realized based on wireless transmission and SQLite database. The accuracy of the proposed method is verified by experiments. The example of motor digital twin established in this paper provides a typical example for the establishment of equipment digital twin system, and also lays a foundation for the further realization of remote intelligent operation and system life prediction.

Power transformer is an important equipment of power system, its short circuit will produce huge short circuit impact force, which will harm the safety and stability of power system. When the transformer is subjected to short circuit, the winding will produce plastic deformation, which will change its winding structure and affect its structural stability, so it is important to study the transformer short circuit damage. Based on the principle of short circuit, this paper calculates the distribution of magnetic leakage and electromotive force in transformer short circuit. In order to consider the material properties, the mechanical properties of copper wire and pad in winding are studied to study the damage of short circuit impact on winding. Finally, the cumulative damage effect of multiple short-circuit shocks on windings is verified by the actual transformer multiple short-circuit experiments.

New rural areas are faced with the rapid growth of power load and the massive access of distributed photovoltaic (PV), which makes the voltage quality problem of rural distribution network prominent. In the paper, a voltage governance optimization method is proposed to improve the voltage quality, which takes governance effectiveness, comprehensive cost, and power outage time as optimization objectives. Reducing solution scope is applied to reduce calculation time and computing resources for the optimal governance scheme. Firstly, a multi-objective optimization model is built, and the constraints on node voltage, power balance and devices are given. Then, the optimization model is solved by using the steps of cause analysis, screening measures, further limiting measures and gear ranges, and power flow calculation nested genetic algorithm. Finally, the proposed method is analyzed and compared in a application scenario of medium voltage distribution lines including small hydro-power and distributed PV. Results show that the proposed voltage governance optimization method is superior to the traditional scheme.

Transformer is an important electromagnetic equipment in power system, the real-time monitoring of its status is very important for the safe and stable operation of power grid. At present, finite element software is usually used to calculate the core magnetic field, but it takes a long time to calculate because of the large number of meshes, and it is difficult to meet the requirement of real-time monitoring of transformer status. In order to solve this problem, a modeling method of transformer core magnetic circuit considering the distribution of rotating flux in corner and T-zone is proposed. In this method, the core is divided into several magnetic circuit segments, and each magnetic circuit segment is finely divided to meet the requirement of calculation accuracy. In solving the model, the nonlinear equations of magnetic flux in the core loop are established by using the electromagnetic duality relation, and the equations are solved by piecewise spline interpolation of BH curve, which speeds up the solving speed of the magnetic field. Finally, the transformer model is established by finite element simulation software, and the effectiveness of the proposed calculation method is verified by comparing with the simulation results.

The quality of power output from photovoltaic (PV) systems is easily influenced by external environmental factors. To mitigate the power fluctuations that can impact the quality of electricity in the grid, this paper establishes an optimization model for capacity configuration of hybrid energy storage systems based on load smoothing. The net load data is processed using the Fast Fourier Transform (FFT) for frequency analysis. Considering various factors such as economic costs, capacity loss, cycle life, and state of charge of the energy storage devices, the objective is to minimize the total cost of the energy storage system. The Particle Swarm Optimization and Differential Evolution (PSO-DE) fusion algorithm is employed to determine the compensation frequency bands for each energy storage device and calculate the optimal capacity configuration for the hybrid energy storage system. Using a PV power station in Australia as an example, this paper compares different capacity configuration schemes for the hybrid energy storage system and proposes the optimal capacity configuration for the PV power station's hybrid energy storage system.

The existing pumped storage power station generator outlet circuit breakers all use SF6 circuit breakers. The multi-break parallel design of vacuum circuit breakers is an effective way to solve the inadequate rated current of the vacuum interrupter. However, multi-break parallel structures suffer from uneven contact resistance and uneven currents caused by unsynchronous breaking, leading to problems such as interrupter life decay and even opening failure. This paper investigates the multi-break parallel current equalization characteristics of generator outlet circuit breakers and their key influencing factors. Firstly, the design of multiple guide bars in parallel is proposed by analyzing the equalization characteristics of different shapes, lengths and numbers of guide bars as well as considering the contact resistance variation; then a multi-physics field model based on the finite element method for multi-break vacuum circuit breakers was established, considering the static mean flow characteristics under the initial and multiple opening deviations, and analyzing the effect of skin effect on the current distribution in the guide rod section; finally, the equalization characteristics of the flow in the dynamic case when the gates are not synchronous are considered. The simulation results show that the use of long guide rods can achieve a good equalization effect, the skin effect does not have a significant impact on the uniform distribution of the current of a single guide rod, and the maximum current deviation between the guide rods is 3.4%.

There is a lack of some effective monitoring means in the operation of dry hollow reactor. In order to clearly understand the important state quantity related to the operation reactor, simulation modeling is adopted to simulate the state of dry hollow reactor in operation, simulate the short-circuit fault between turns, and analyze the current change of the star arm. It is concluded that for dry hollow reactor, Star arm current detection is an effective means of detection.

In order to remove the large amount of white noise mixed in partial discharge (PD) signals, this paper proposes a novel denoising method that combines optimized variational mode decomposition (VMD) and threshold denoising method. In this work, particle swarm optimization algorithm was introduced, based on the principle of minimum envelope entropy, to adaptively solve the difficult selection of VMD parameters, and removes white noise in PD signals through threshold denoising. The results of simulation, actual noise reduction analysis, and comparison with wavelet thresholds show that the proposed method has better noise reduction effect. The improved methods may also be contributed to the denoise of PD under high dv/dt and high frequency voltage.

The breaking and closing operation process of bi-stable permanent magnetic actuator (BPMA) is flexible and controllable, and can achieve the permanent magnet locking effect at the steady-state position. However, during its operation, the breaking and closing air gap electromagnetic and permanent magnet flux linkage are coupled, which will affect the action characteristics of the moving core. Therefore, this article constructs the voltage balance equation of the breaking and closing coils through the equivalent circuit of coil decoupling, and analyzes the parameters that affect the coupling phenomenon; Design a current closed-loop to control the actuator. Through co-simulation of LabVIEW and Multisim, analyze the influence of the electromotive force induced by the coupling phenomenon at each stage of the breaking and closing process, explore the mechanism of the coupling phenomenon, and the impact of the coupling effect on the action process; Finally, experimental waveforms were obtained through an embedded control system, and the accuracy of the simulation was verified by comparing the simulated waveforms. This indicates the reliability of the coupling phenomenon analysis through simulation.

The integration of renewable energy into the power grid poses inherent 1 risks and complex challenges due to the volatile nature and seasonal variations of these energy sources. Energy storage clusters play a pivotal role in addressing these issues by providing flexible and responsive energy storage capabilities. They effectively balance the supply and demand, maintain grid stability, and ensure the reliability of grid operations. Demand analysis is imperative for optimizing the operation of individual energy storage stations within a cluster. It entails a comprehensive examination of their characteristics, such as peak shaving capacity and frequency regulation capacity, to develop effective deployment strategies and power dispatch plans. This article proposes a power allocation strategy for coordinating multiple energy storage stations in an energy storage dispatch center. The strategy addresses the temporal demands of peak shaving and frequency regulation in the power grid. It quantifies the minimum capacity, power, rate and duration time requirements for energy storage stations to actively support the grid, helping the dispatch center make informed decisions and identify suitable stations for each demand scenario.

The traditional Weighted Average Current (WAC) control method loses its loop-order reduction characteristic due to control delay, resulting in significant instability risk for the system in weak grid conditions. This paper, based on the equivalent impedance model, analyzed that the main cause of system instability is the introduction of a positive feedback loop associated with grid impedance through the voltage feedforward channel, resulting in phase lag. To address this issue, the paper proposes the introduction of a Second-Order Generalized Integrator (SOGI) in the voltage feedforward channel to attenuate the impact of the positive feedback loop on the system, improve the phase margin of the equivalent output impedance in the medium to low frequency range, and enhance the system's adaptability to a wide range of grid impedance variations. Furthermore, in order to eliminate control errors in the indirect control of WAC and enhance the system's background harmonics suppression capability, the quasi-Proportional Resonant (QPR) controller is combined to improve the quality of grid-connected current. Finally, the effectiveness and feasibility of this improved WAC control strategy are verified through simulation in MATLAB/Simulink.

Electrical equipment is a crucial infrastructure in the power system, susceptible to quality issues, and posing threats to the power system. Tracing quality problem causes helps prevention while predicting quality status based on these causes enables swift action. Most studies target quality problem identification, neglecting cause tracing. This paper introduces the concept of quality tracing, prediction, and early warning using LightGBM-SHAP. Firstly, LightGBM is employed to model the relationship between quality-related factors and target variables. Subsequently, the SHAP method is applied to analyze the significant importance of each influencing factor and deeply assess its impact pattern. This facilitates the effective identification and tracing of quality-influencing factors within electrical equipment. Finally, pivotal influencing factors are selected based on their characteristic importance, and LightGBM is utilized to predict the quality issues. Illustrating with transformers as an example, the predictive and early warning capabilities of the LightGBM-SHAP model are proposed to outperform the comparison model. Furthermore, it effectively dissects the causes of quality problems and offers decision support for quality tracing, prediction, and early warning in the realm of electrical equipment.

Wireless charging technology shows great promise for efficient power transfer. However, the effectiveness of power transfer largely depends on various operational parameters such as coupling coefficients, load resistance, and operating frequency, making it challenging. To address this issue, a novel fuzzy control algorithm is proposed in this paper to continuously track the optimal efficiency point of a wireless charging system. First, this paper designs the topology of the wireless charging system and analyzes its optimal efficiency point. Then, it proposes the control scheme, which can adjust all the parameters and maximize its efficiency. Finally, the scheme is then evaluated through simulations and experiments and the results show that the proposed control scheme effectively optimizes power transfer and enhances the overall performance of the wireless charging system.

In order to eliminate the DC-side power pulsation of high-voltage direct-mounted battery storage systems, a bridge-arm multiplexed symmetrical half-bridge power decoupling structure is constructed to achieve decoupling control of the pulsating power. Firstly, the causes of pulsation power generation and the principle of decoupling control are described. Then, a virtual quadrature is constructed by applying the Second-Order-Generalized-Integrator and the mathematical model of power decoupling control in DQ coordinate system is obtained by coordinate transformation. On this basis, the corresponding passive controller is designed according to the passive control theory, and the power decoupling control strategy is proposed in combination with the pulsating voltage feedforward. Finally, a simulation model is established in PLECS, and the simulation results verify the effectiveness and correctness of the proposed power decoupling control strategy.

The corrosion behavior of carbon steel, a grounding electrode material for power grids, in the northwest saline soil environment was studied by weight loss method, polarization curve and electrochemical impedance spectroscopy (EIS). The results show that the grounding electrode materials all undergo oxygen uptake reaction in the saline soil environment under laboratory simulated saline soil conditions, and the corrosion types are all localized corrosion. The grounding electrode does not increase the corrosion rate with the increase of alkalinity, when the pH = 12, passivation reaction occurred, corrosion was inhibited. After adding 2%, 4% and 6% chloride ions respectively and the negative direction of the corrosion potential shift is obvious, the corrosion rate is obviously accelerated, but at 4% the corrosion rate is the fastest, is only pH 22 times. The synergistic effect obviously accelerated the corrosion of the grounding electrode material and shortened the service life of the material.

Insulation structure changes, operational state variations, and internal defects in a 750 kV autotransformer can cause changes in the capacitance of the transformer windings, resulting in asymmetrical capacitance parameters of the three-phase windings and unbalanced foundation voltage on the low-voltage side winding bus. This paper offer a capacitance state evaluation fashion for 750 kV transformer windings based on BP neural network. By constructing a simulation model of a three-phase 750 kV autotransformer and considering the actual range of variation in winding capacitance parameters, a measurement dataset of unbalanced voltages on the low-voltage winding is obtained. The unbalanced voltage of the low-voltage winding and the winding capacitance are selected as input and output datasets, respectively. Based on BP and PSO-BP neural networks, transformer winding capacitance state evaluation models are established and trained. The capacitance state of the windings is evaluated and verified through simulation experiments exploitation unbalanced voltage data from a certain 750 kV transformer. The verification consequence show that the PSO-BP neural network model has better forecasting accuracy.

The pulse power supply based on capacitor has the characteristics of simple structure, mature technology and reliable operation, and it is widely used in electromagnetic launcher. The improvement of system efficiency can reduce the volume and weight. The model of the launching system has been established by discrete method with s-domain. This model has been verified with the Pspice model. Based on the established model, parameters sensitivity analysis including internal resistance, initial voltage and capacitor value is conducted to obtain the sensitivity parameters under the time sequence. The results show that internal resistance is the most sensitive parameter in the launching system.

The sorting into groups is a critical step in the cascade utilization process of retired power lithium-ion batteries. In order to enhance the consistency performance of grouped batteries in cascade utilization, the various static and dynamic features based on battery charge and discharge experimental data are extracted in this paper, A two-tier sorting architecture is established and the combined sorting of static and dynamic features are achieved. In the first-tier sorting, fuzzy logic is employed in combination with static battery characteristics for an initial sorting. The simulated annealing algorithm is used to optimize the initial selection of cluster centers in the K-means algorithm. In the second-tier sorting, an improved K-means algorithm is applied to conduct a secondary sorting based on the dynamic characteristics of the batteries. Following the second-tier sorting, the consistency of open-circuit voltage among battery groups improved by 92%, the consistency of internal resistance improved by 94%, and the consistency of capacity improved by 33%. It can be observed that the approach proposed in this paper effectively enhances the consistency of retired battery grouping.

In order to improve the accuracy and efficiency of fault arc detection, this paper adopts the characteristic quantity of arc current wavelet decomposition coefficient to pre-judge arc signals, and adopts the wavelet Mallet algorithm to perform multi-scale decomposition of arc signals. The decomposed wavelet coefficient of arc current wave is taken as the characteristic quantity, and an adaptive threshold algorithm is proposed for detection. According to the results of the threshold detection algorithm, the current signal is selectively input into the residual neural network, which effectively improves the detection accuracy. Finally, the feasibility of detecting fault arc with residual neural network is verified, and its accuracy rate reaches 98.73%.

In order to study the vibration characteristics of the enhanced electromagnetic railgun, a full model of barrel vibration coupled with electrical, magnetic and structural Multiphysics simulation was established based on the LS-DYNA platform. Combined with theoretical analysis and experimental research, the preliminary time-frequency characteristics of barrel vibration signals were obtained. The theoretical analysis shows that the frequency component of the barrel vibration signal is mainly related to the excitation frequency, and the excitation includes the electromagnetic repulsion force between the rails and the impact of the armature on the rails (that is, the armature-rail contact force). The experiment shows that the trend of vibration signals at a certain position of the barrel in the time domain is related to the position of the armature. Before and after the armature passes through this position, the amplitude of barrel vibration is relatively slow, mainly caused by electromagnetic repulsion between the rails; When the armature passes through this position, the vibration amplitude of the barrel is relatively large, mainly caused by the impact of the armature on the barrel. In frequency domain, the vibration frequency band caused by electromagnetic repulsion force is lower, and the vibration frequency band caused by armature-rail contact force is higher. The trend obtained from the simulation results is basically consistent with the experiment, and based on further analysis of the simulation, the impact force on the barrel will slowly increase in the time domain after the armature is activated. As it approaches the muzzle, the impact force will slowly decrease, while in the frequency domain, it shows an increasingly concentrated trend in the high-frequency band.

In response to the problem of slow differential protection action caused by the continuous blocking of the second harmonic braking criterion during the actual inter turn short circuit fault of ultra-high voltage converter transformers, this article analyzes the characteristics of inrush current and developmental inter turn short circuit faults in converter transformers through theoretical analysis. It is found that by comparing the corresponding differential current of two parallel operating converter transformers horizontally, the inrush current and inter turn fault of converter transformers can be identified. Based on this, Propose an optimization method for differential protection of converter transformers based on lateral differential current identification. Through on-site waveform recording and real-time digital simulation system (RTDS) simulation verification, the proposed protection method has high speed in the event of inter turn short circuit fault and second harmonic braking criterion mislocking. For actual faults that expose problems, the protection action time is shortened from 56 ms to 23.6 ms. At the same time, it ensures reliable and reliable operation under various inrush current conditions.

The vast majority of electrical equipment will be set in the outdoors, because some electrical equipment needs to communicate with the outside world, and the outdoor environment can provide better signal transmission and reception quality, so as to ensure the normal operation of the equipment. However, in the summer weather is hot, electrical equipment for a long time in the extremely hot environment, its internal temperature may exceed the normal working range, will reduce the reliability of equipment operation and service life. For the cooling of electrical equipment is less studied, this paper proposes the use of radiation cooling film to reduce the temperature of outdoor electrical equipment. This paper uses the control variable method and statistical analysis method to conduct experiments on the performance effect of radiation cooling film. The experiment shows that the surface of the outdoor equipment after attaching the film during daytime work can be reduced by 10–14 ℃. This paper applies the radiation cooling technology to electrical equipment for research, which has good market application prospects and certain reference value.

Based on an augmented railgun system, the influence of the current rising time on the initial velocity is studied by simulation and experiment. The driving current with the faster rising time does not increase the muzzle velocity of launch system under the same discharge voltage. When the rising time is raised to a certain extent, the discharge current peak and the initial velocity will be decreased. The conclusion is instructive to the optimal design of pulse power source for electromagnetic launch system.

The curing curve of epoxy resin was determined using a differential scanning calorimeter (DSC) to investigate the preparation method of the epoxy resin. A comprehensive experimental study was conducted on the mechanical properties of glass fiber-reinforced epoxy resin composites with glass fiber content ranging from 40% to 50% using a universal testing machine and a pendulum impact tester. The stress-strain curves of the materials at different glass fiber contents were obtained, revealing the influence of glass fiber content on tensile strength, compressive strength, and impact strength of the materials. By analyzing the fracture morphology of the specimens, the fracture mechanisms were revealed. The results showed that the glass fiber-reinforced epoxy resin composites exhibited excellent mechanical properties, and increasing the glass fiber content significantly improved the mechanical performance of the composites. Analysis of the specimen surfaces indicated that tensile failure was primarily due to shear fracture and delamination damage at the glass fiber-epoxy resin interface. Cracks appeared on the surface of the compressed composites, with damage in the form of delamination and resin cracking. During impact failure, fiber fracture and interlayer separation of glass fibers were observed on the impact surface, while delamination damage occurred on the impact backside of the glass fibers.

Vacuum circuit breakers are an environmentally friendly electrical equipment. At present, vacuum circuit breakers are widely used in 40.5 kV distribution power system with the excellent opening capacity and low maintenance loss. Decreasing the use of high greenhouse gas SF6 is an urgent task to build an environmentally friendly power system toward the dual carbon goal. Developing the vacuum circuit breakers to transmission level is one of the effective ways to replacing SF6. In the vacuum arc, the arc evolution process determines the performance of the circuit breaker. The arc plasma distribution in the inter-electrode region is an important characteristics of the vacuum arc evolution process. Because it is difficult to measure the arc parameters in the experiment, the present work establishes a magneto-hydrodynamic model to calculate the arc parameters. The current density distribution characteristics is also calculated in the model and it is found that the current constriction phenomenon mainly occurs near the anode. Moreover, the influence of opening velocities and magnetic fields on the arc plasma is investigated. The higher magnetic field and lower velocity could suppress the arc constriction. The results can provide a theoretical reference for the development of transmission level vacuum interrupters.

In order to solve the problem of low efficiency of traditional intelligent contactor performance test, this paper proposes a contactor dynamic characteristic test and analysis system based on NI CompactRIO, which is convenient for measuring the performance index of intelligent contactor. The system includes a Human-Machine-Interaction(HMI) interface, which can control the action of the contactor to be detected and collect signals in the host computer platform. According to the trend of the collected signal waveform, the performance indexes of the contactor, such as the closing/opening time, the closing/holding power, are calculated. The system also has the functions of cyclic switching test and automatic data storage, which greatly improves the automation level and efficiency of the test. It provides data support for the improvement and optimization of the control strategy of intelligent contactor.

Optical fiber current transformer (OFCT) is widely used in flexible DC transmission to improve the ability of information perception of power grid, and optical fiber insulator is the key component of OFCT to provide insulation and protection. However, discharges in optical fiber insulator seriously affect the stable operation of the power system. Here, the effect of defects including bubbles and cavities on the electric field distribution in insulator is explored to figure out the inner discharge mechanism. A ± 400 kV optical fiber insulator 3D simulation model is constructed in COMSOL Multiphysics, and differences in the electric field distribution in the insulator are compared and analyzed by finite element method under different defects. The results show that the bubbles do not have a significant effect on the electric field distribution. However, when there is a cavity, the inherent electric field distortion on the fiber sheath due to the mismatched potential caused by the semi-conductive fiber coating layer will extend into the cavity. The electric field strength at the interface between the cavity and the fiber sheath is up to 6 kV/mm, which exceeds the breakdown strength of the air. Therefore, the existence of the cavity causes the air discharge on the surface of the optical fiber sheath, which can make damage to the optical fiber sheath and leads to insulation failure.

The mathematical model of permanent magnet motor is analyzed in dq coordinate system, and a vector control strategy is designed for hybrid electric vehicle and other applications. When the motor running speed is lower than the rated value, MTPA control is used to enhance the motor’s torque output capacity and reduce its energy loss, and the DC bus voltage utilization rate is determined according to the AC direct axis voltage calculation. When the inverter reaches saturation, the phase Angle of the stator current vector is adjusted by the weak magnetic leading Angle, so that the motor can run at high speed and stably. At the same time, a decoupling module is added to reduce the interference of coupling terms when the speed is high. Considering the heat consumption of the controller under rated working conditions, the cooling of IGBT module is realized by water cooling. The experimental results show that under this control strategy, the speed fluctuation of permanent magnet motor is small, the torque response speed is fast, and the temperature running speed range is wide. The results of thermal simulation show that this water-cooled cooling structure can meet the heat dissipation requirements of motor controller.

Based on dsPIC33F series microcontroller and the full bridge drive circuit built by BridgeSwitch1267C integrated half-bridge chip, this paper designs an integrated intelligent contactor controller with the function of voltage drop resistance: The volume and cost of the control module are further reduced by reusing the rectifier output voltage regulator capacitor as a backup power supply; With the intelligent control strategy of flux closed-loop starting, silent energy saving reliable holding and negative pressure rapid breaking, the control module not only has the function of resisting voltage drop, but also takes into account the dynamic performance of contact bounce suppression, noise elimination and arc erosion reduction; By controlling the drive circuit alone, the control module can gently switch among starting, normal holding, voltage drop resistance holding and breaking, which reducing the coil excitation loop and increasing the reliability of the control module.