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

The transformer is a key link in the power system, and its internal temperature has a decisive effect on the health status of the transformer and various decisions on it. Therefore, it is of great significance to study how to accurately predict the oil temperature of transformers. In this paper, a method for predicting transformer hot spot temperature based on digital twin technology is proposed. First, a transformer twin model is built in the virtual space, and multi-physics field coupling simulations are performed on it under various working conditions, and the transformer oil temperature data is saved as the twin body temperature database. Then combined with algorithms such as the extreme learning machine (ELM) in the neural network, the database data can be learned and the oil temperature can be actively predicted. Finally, the predicted temperature is compared with the actual temperature data to verify the accuracy of this method. The results show that the extreme learning machine algorithm has better prediction accuracy than other algorithms. This hot spot temperature prediction method based on digital twin technology can provide a certain reference value for the stable operation of the power system.

Closing resistors are mainly used in line circuit breakers of 800 kV and above and AC filter circuit breakers of 550 kV and above to suppress the closing inrush current and transient overvoltage during the closing process of circuit breakers. Due to the special characteristics of its operating conditions, it needs to be cast and cut frequently, resulting in frequent failures of the closing resistor piece. In this paper, the electric field and modal simulation model of the closing resistor stack is established. Simulation results show that when the closing resistor is broken, the electric field around it produces distortion, which is 39% higher than the normal working condition, harming the normal operation. Modal simulation results show that the resonance frequency of the resistor stack in the first 6 orders is 18.7–43.37 Hz, which is close to the intrinsic frequency of general trucks and vans, and the vibration should be reduced as much as possible to avoid resonance of the resistor stack in the transportation process to ensure the reliability of the product.

This paper presents a comprehensive diagnostic method for cable connection faults in permanent magnet synchronous motor (PMSM). The method utilizes high-frequency voltage injection at zero speed and considers single and multiple faults, including the misconnection of two-phase powerlines, disconnection of one-phase powerlines, and cable swap of position sensors. Mathematical derivations of the response current are provided and an offline diagnosis is performed using a support vector machine (SVM). The SVM is trained with a range of response signals, and feature extraction algorithms are employed to enhance the classification accuracy. Experimental results demonstrate the effectiveness of the proposed method in detecting, identifying, and locating faults, thereby achieving a comprehensive and highly accurate diagnosis for various PMSM cable faults with different causes. This contributes to the overall reliability of the system.

As a large number of grid-following converters (GFLs) have joined the power system, transient characteristic of the power system is profoundly being changed. Aimed at the case of coupling system integrated by GFL and synchronous generator (SG), it is necessary to analyze synchronization stability of coupling system in the large-disturbance case. To address that, this paper investigates the coupling system between GFL and SG firstly. Then, the equivalent model of coupling system is derived. Next, transient stability analysis of GFL based on the equivalent model is conducted to detect the transient instability mechanism. Two instability modes of GFL are defined. Finally, time-domain simulation results verify the correctness of theoretical analysis.

As cities grow, cables play an increasingly important role as part of the power transmission system. But as the number of cables increases, so do the safety hazards that come with them: the generation of cable arcs and even the start of fires. Cable fire blankets are necessary to protect against the initial stages of cable fires. In this paper, three different pairings are compared and analyzed by a combination of experiments and simulations. These include Kevlar-Teflon, Polyimide-Teflon, and Kevlar-Polyimide material pairings. The study illustrates the possibilities of polyimide materials for the application of cable fire blankets. The bearer of the simulation part is COMSOL software. By combining experiments and simulations with each other, the excellent fire protection properties as well as the arc resistance of polyimide are illustrated for the use of polyimide in cable protection blankets and also provide theoretical support for the application of polyimide in the field of cable protection.

CORC cables have the advantages of high current density, low inductance, and ease of manufacturing, making them one of the best candidate cables for fusion projects. In fusion projects, there is a huge background magnetic field, and the current carrying capacity of the CORC cable can reach the level of ten thousand amperes. Therefore, CORC cables are often affected by significant transverse compressive electromagnetic forces. Excessive transverse compression load can cause irreversible degradation of the current carrying capacity of the CORC cable, thereby affecting its normal operation in fusion projects. Therefore, it is crucial to improve the ultimate transverse compressive load that CORC cables can withstand. This article investigates the influence of different winding methods of superconducting tapes under arc-shaped load blocks, as well as the copper plating thickness of superconducting tapes, on the transverse compression load performance of CORC cables. The experimental results show that reducing the number of layers, increasing the number of superconducting tapes per layer, and reducing the copper plating thickness of superconducting tapes can effectively increase the ultimate transverse compression value of CORC cables when the number of superconducting tapes is constant; When the number of superconducting tapes per layer is fixed, increasing the number of superconducting tape layers can also increase the ultimate transverse compressive load value of CORC cables. When the number of layers is fixed, increasing the number of winding layers of the superconducting tape material in each layer can also increase the ultimate transverse compressive load value of the CORC cable. The research results of this article provide a theoretical basis for the parameter design of CORC cables in the future.

Image fire detection technology is a new fire detection technology, which often needs to segment fire images according to their brightness, color, texture and other characteristics. The more features that are used, the more detailed the segmentation is often performed. This paper studies the application of fractal features in image segmentation, proposes an improved image box dimension measurement method without the fitting algorithm for many times, and finally simulates the oil fire, which provides some reference for the detection of oil fire.

The control problem of Interior Permanent Magnet Synchronous Motor (IPMSM) under external disturbance has always been a difficult problem in the industry, although H∞ control can effectively improve the robustness, it is difficult to solve the Game Algebra Riccati Equation (GARE) analytically due to the time-varying uncertainty of motor parameters. To solve this problem, this paper proposes an off-policy reinforcement learning method, which uses the data-driven way to learn the solution of GARE online, completely without the mathematical model of the motor, successfully realizes the H∞ optimal control of the time-varying system, and applies it to the current control of IPMSM. Firstly, using the saddle point theory of game theory and the linear discrete mathematical model of the motor, the H∞ optimal control problem was transformed into a two-player zero-sum game problem, and the GARE equation was constructed. Then, the reinforcement learning algorithm based on Actor-Critic framework is used to update the Q function and the strategy by using the input and output data of the system, and the optimal H∞ controller satisfying Nash equilibrium is learned. The test results of Processor In Loop (PIL) prove the feasibility of the proposed scheme, and its performance is far superior to PI control.

Boron Neutron capture Therapy (BNCT) is an advanced targeted radiotherapy method with great application prospect and rapid development. BNCT has become a new hotspot in the research and development of energetic particle therapy and one of the important options for future tumor treatment. The DC high-voltage accelerator is an important component of the accelerator based BNCT device, which utilizes a DC high-voltage electric field to accelerate charged particles. The DC high-voltage generation system is one of the indispensable components of the DC high-voltage accelerator, providing megavolt level DC high-voltage for the DC high-voltage accelerator tube. According to the design requirements of the prototype project of the 2.5 MV accelerator Neutron source device for the DC high-voltage power supply, this paper first proposes the structural design scheme of the 2.5 MV DC high-voltage generation system, and then briefly introduces the components of the 2.5 MV DC high-voltage generation system, mainly including controllable silicon DC stabilized power supply, high-frequency high-voltage oscillator, high-frequency high-voltage transformer and voltage doubling rectifier system, And briefly analyzed the principle of the core component of the DC high voltage generation system, the voltage doubling rectifier circuit, derived the output voltage of the voltage doubling rectifier circuit, and simulated the 2.5 MV voltage doubling rectifier circuit in this study. Finally, the output performance of the 2.5 MV DC high voltage generation system was experimentally tested. The experimental results show that the 2.5 MV DC high-voltage generation system meets the design requirements of the 2.5 MV accelerator Neutron source device prototype project, and lays a certain foundation for the physical experiments of the 2.5 MV accelerator Neutron source device prototype.

In order to improve penetration rate of new energy on-grid power generation, reduce carbon emissions, promote energy security and environmental protection, and solve the power quality problems caused by frequency and voltage fluctuations in photovoltaic on-grid power generation, the paper uses Voltage-controlled Virtual Synchronous Generator (VVSG) technology to control grid-connected inverters, which can enable photovoltaic grid-connected power generation to actively take part in the frequency and voltage regulation of power grid, meanwhile it can making the operation of the power system more secure and stable. In the paper, combined with the characteristics for photovoltaic power generation system, a hybrid energy storage link is added, it is used to stabilize DC bus voltage and perform peak shaving and valley filling, set a VVSG mathematical model, and this control strategies of each part, active power-frequency control and reactive power-voltage control are analyzed. Finally, this effectiveness of control strategy is verified by establishing a simulation model in Matlab/Simulink.

In this paper, a generalized model of underground refuge is established with the size of a typical pumped storage power plant, and the values of rock parameters, contact surface parameters, stresses and boundary conditions are determined in the surrounding layers of the model. In order to analyze the influence of rock dip angles on the relaxation and deformation of underground caverns, we conducted numerical simulations on ten different rock dip angles. Comparison analysis of the deformation displacement and relaxation deformation characteristics of the surrounding rock under ten different inclination angles of rock formations is carried out, and the influence of the inclination angle of rock formations on the relaxation deformation of underground chambers is concluded.

More Electric Aircraft (MEA) will drive sustainable development in the aviation industry, reducing environmental pollution and noise. Electro-Mechanical Actuators (EMAs) can carry out tasks such as rudder deflection and have great influence on the MEA power system, especially when multiple EMAs act together. However, most previous research focused on the enhancement of EMA performance or the input characteristics of a single EMA, in which the impact of multiple actuators working together on the power system has not been touched. In this article, an MEA power system model with multiple EMAs is built and the impact of multiple EMAs on power system stability is analyzed. Firstly, the functions of different EMAs are reviewed and the working scenes of multiple cooperative EMAs are designed. Afterward, the control schemes of speed-controlled and position-controlled EMAs are studied, after which the power system model, including generators, uncontrolled rectifiers, and EMAs, is built. Finally, the impact of EMAs on MEA power system stability is simulated in Simulink. The results show that speed-controlled EMA impacts the power system just when the command target changes and lasts for a relatively short period of time. In addition, position-controlled EMA continuously impacts the power system. To conclude, EMAs may cause significant voltage fluctuations in the power system and should be addressed by implementing control methods involving supercapacitors and batteries.

Electromagnetic launch technology is a kind of launch technology that uses electromagnetic force to propel an object to high speed or ultra-high speed, which has incomparable advantages over traditional launch methods in terms of launch speed, launch efficiency, controllability, concealment and cost. In order to solve the problem of low service life and low reuse rate caused by ablation damage of copper alloy slide rail in the practical process of rail electromagnetic launcher, an equivalent scaling model under electromagnetic thermal multi-field coupling is established in this paper, and the overall distribution of electromagnetic field and temperature field are simulated. It is concluded that the current density and magnetic induction intensity are concentrated in the armature groove and tail and around the contact point between the armature and the slide rail, and the heat is concentrated in the armature groove and the slide rail. These areas are where the electromagnetic launcher is prone to ablation damage. It provides the guidance for the manufacture and test of electromagnetic launcher.

Since the proposal of the strategy in strengthening the country with science and technology, electromagnetic emission technology has gained wider and wider application in military, aviation, industry and other fields. Clarifying the thermal damage mechanism of the armature-rail under extreme impact conditions and improving the reuse rate and service life of the device have become a hotspot for researchers at home and abroad. Based on previous achievements, this paper adopts finite element simulation methods to establish a more comprehensive three-dimensional model of the electromagnetic launch system. The temporal and spatial distribution characteristics of the transient temperature at the armature-rail interface are investigated under the coupling analysis of electromagnetic thermal multi-physical field. Furthermore, the influence of externally applied current waveform on temperature peak is analyzed, and the temperature rise mechanism is also analyzed based on the theories such as heat source and skin effect. The series of studies conducted are of great significance for clarifying the working performance of electromagnetic emission systems and guiding the manufacturing, operation and maintenance of the equipment.

Aiming at the influence of surface work function and internal atomic structure of nanoelectrodes with different crystal orientations on the theoretical mechanism of vacuum breakdown, the current electrodynamically-coupled molecular dynamics and particle simulation method (ED-MD-PIC) was used in this paper. The effect of crystal orientation on the vacuum breakdown characteristics of copper nanoelectrodes was studied by comparing the evolution of characteristic parameters of different crystal orientations ({100}, {110}, {111}). The emission current and the shielding effect of space charge on the local electric field at the tip of the nanoelectrode at the initial time of different crystal orientations increase with the decrease of the work function of the crystal surface of the material. The necking, sharpening and evaporation of atomic clusters of nanoelectrode tips with different crystal orientations lead to differences in field enhancement factor and internal heat transfer rate. The higher electric-thermal field is the main reason for the lower critical electric field and vacuum breakdown delay of Cu {111} electrode. The maximum difference of the critical electric field of vacuum breakdown of nano-electrode with different crystal orientations is less than 7%.

Considering the mismatch of the intrinsic vibration frequency between the cable and the mechanical device laid in the bridge offset, the vibration mode of the high-voltage (HV) cable and the mechanical device laid in the bridge offset is vital for the condition monitoring of the power transmission systems on the bridge. However, the vibration characteristic of the cable laid in the bridge offset has not been studied by simulation. In this paper, a model considering the electromagnetic force has been established. The results show that the displacement and stress reach their maximum values at the junction between the cable and the mechanical device. The maximum displacement is observed at the right of the junction, measuring 30 μm, while the maximum stress is observed at the left end of the junction, measuring 90 kPa. Besides, the vibration of the mechanical device is trend to move to low frequency.

Driven by the sustainable development strategy of ‘’dual carbon’’, the consumption situation of renewable energy in China is worrying, and it is urgent to need more flexible control resources to adjust Power system networks. To some extent, electric vehicles can interact with the power system network in both directions. When the electric vehicle is not in the driving state, it can transmit excess electrical energy back to the grid, thus playing the role of an energy storage device; And when an electric car needs to be charged, it can take power from the grid to charge it. A large number of electric vehicles continue to be put into market use, and if their charging behavior is not properly guided, it will cause a huge impact on the power system network. Therefore, the focus of this paper is to use the electricity price elasticity matrix to guide the charging behavior of users, It reduces the impact on the power system network, standardizes the charging behavior of electric vehicle users, and ensures high utilization of renewable energy To achieve the maximization of bilateral benefits for both the grid and users in the optimization process, it shows that under the consideration of multiple interests The most effective scheduling method is to adopt the collaborative optimization strategy.

Ultraviolet (UV) irradiation is an environmentally friendly method for material modification. In order to explore the effect of UV irradiation on surface properties of epoxy resin and further explore the feasibility of this method on improving surface flashover of epoxy resin, in this paper we experimentally study the surface morphology and chemical structure of epoxy resin after UV irradiation. It was shown that after irradiation, the surface morphologies and roughness of the samples shown little change. The FTIR results showed that after UV irradiation, the O-H and C=O groups on the surface were increased, while the content of CH2 and CH3 groups was decreased greatly. We further studied the surface chemical components by XPS and it was revealed that the C-C/C-H and C-O-C bonds on the surface decreased significantly by UV irradiation, and the C-O-H and C=O bonds increased significantly. Through molecular simulation calculations, it was found that the bond energies of C-O-C, C-H, and C-C bonds in epoxy molecules are low, and thus they were prone to fracture by UV irradiation. This study elucidated the mechanism of UV irradiation on changing the surface chemical structure of epoxy resin, and provided a basis for improving the surface flashover performance of epoxy resin by UV irradiation.

The fast vacuum switch can reach a high open velocity. It is a key part of the mechanical high voltage direct current circuit breaker. The fast vacuum switch is mainly driven by the current flowing repulsive coil. Now many researchers focused on the optical designed of the repulsive mechanism. Some common faults on the key component, including the repulsive coil, the repulsive disk and the bistable spring, were seldom discussed. In order to get a better understanding of the common fault, this paper carried out simulations about the aging of repulsive coil and bistable spring, the deformation of repulsive disk. The simulation results indicated that the aging of repulsive coil and bistable spring showed small effects on the motion of the fast vacuum switch. The deformation of repulsive disk showed obvious effect on the opening process.

In order to study the insulation characteristics of glass fiber/epoxy composites under extreme physical fields of typical electromagnetic coil launchers, 3240 and G11 glass fiber/epoxy composites were used as research objects. The temperature distribution characteristics of electromagnetic coil launchers were analyzed by finite element method, and an equivalent test platform was constructed for thermal aging test. Combined with macroscopic and microscopic tests, the aging mechanism of glass fiber/epoxy composites for coil launchers was revealed. At 110 ℃, 130 ℃, 150 ℃ aging temperature and 24 h(1 d), 72 h(3 d), 144 h (6 d), 216 h (9 d) aging time. The changes of aging characteristic quantities such as mass loss rate and impact strength of glass fiber/epoxy composites were studied respectively. The thermal aging mechanism of glass fiber/epoxy composites was analyzed by scanning electron microscopy and Fourier infrared spectroscopy. The results show that G11 glass fiber/epoxy composites have smaller mass loss rate, greater impact strength and greater elastic modulus than 3240 glass fiber/epoxy composites, which proves that G11 glass fiber/epoxy composites have better thermal aging characteristics.

The fault characteristics of new power distribution systems are changing significantly due to the development of renewable energy generation. Conventional protection and control methods are difficult to adapt to the problems caused by high penetration of renewables. A wide area protection scheme based on coordination of control and protection is proposed in this paper. The influence of renewable energy sources on distribution system protection is firstly studied. Then partitioning method for active distribution system is introduced to ensure that load can survive and be securely supported by distributed generators in local feeders after system splitting. Next, advanced feeder terminal units and intelligent electronic devices based wide area protection scheme is designed for achieving fast, selective, and reliable operation protection and fault isolation taking account into intentional islanding operation. The activity analysis of the control-protection coordination is conducted as well. Finally, the feasibility and effectiveness of the proposed scheme are analyzed through case studies.

Partial discharge (PD) online monitoring of high-voltage (HV) cable systems has been widely applied as an effective means of online monitoring in power systems. The present PD online monitoring systems' data analysis function, however, differ significantly, and their application has not yet achieved the anticipated impact. Additionally, both locally and globally, there is currently no comprehensive way for verifying and evaluating the data analysis function of HV cable PD online monitoring systems. Therefore, this paper proposes a verification technology for the data analysis function of HV cable PD online monitoring systems. The effective verification schemes and comprehensive evaluation rules have been established. And 3 different types of PD monitoring systems have been verified field by the method. The technical support is provided for the selection of HV cable lines PD online monitoring systems, by verifying the data analysis function of the PD online monitoring systems in this paper. It can also better ensure the intrinsic safety of HV cables and channels.

In this paper, an island DC microgrid composed of wind energy conversion system (WECS), photovoltaic system (PVS), storage battery and electric loads is investigated, and an optimization strategy based on Distributed Projected Subgradient algorithms (DPS) is proposed to solve the problem of power distribution among distributed power sources. First, wind power is used as the main source of power generation and photovoltaic is used as the secondary source, and batteries are used to adjust the power when needed to meet the load demand and maximize the utilization of wind power generation as much as possible, and to improve the charging and discharging process of batteries. To achieve this goal, the DPS algorithm is used to optimize the three subsystems locally, and the power reference values of each subsystem are obtained through information exchange and iterative updating. Then, the local controller adjusts the operating state of each subsystem according to the power reference value to achieve the overall optimized operation of the system. Finally, through simulation analysis, it is proved that using DPS algorithm to deal with the power optimization problem of isolated DC microgrid can well achieve the goals of balancing load supply and demand, making full use of wind power and photovoltaic power generation, extending battery life, and reducing system operation cost.

Multi-micro-source islanding active restoration is an important measure to protect critical loads and regional power supply under extreme conditions. Load self-organization will cause bus voltage unbalance and frequency fluctuation, in which the nonlinear and unbalanced loads will further aggravate the situation, affecting the safe and stable operation of islanded microgrid active recovery. To address this problem, an unbalanced voltage and frequency fluctuation suppression strategy based on model-free predictive control algorithm is proposed. The strategy outputs the optimal reference power to the sag control in real time according to the load demand. By adjusting the optimal power output, the traditional negative sequence compensation algorithm solves the problem of voltage imbalance and voltage and frequency fluctuation when nonlinear unbalanced loads exist simultaneously at multiple PCC points of islanding active recovery. Finally, the parallel restoration strategy based on the black-start principle is formulated, and the effectiveness of the proposed method is verified by building simulation models under different control modes using simulation software.

Aiming at the problem of surge voltage and current under 28 V DC power supply environment of airborne computer, this paper designs two kinds of surge current suppression circuit according to the different power and a surge voltage suppression circuit. Firstly, for circuits with 50 W–100 W power, precise control of surge current peaks is not required, a MOSFET based surge current suppression circuit for airborne system is designed by using the Miller plateau effect of MOSFET. Secondly, For circuits with power less than 30 W whose surge current peaks requires precise control, a low-power current surge suppression circuit is proposed by using NPN transistor and bandgap reference. Simulations and experiments are performed on LTspice and application circuit. The simulation and experimental results show that the proposed method can achieve the surge current suppression and surge voltage suppression and have a good application value.

Ultrasonic motor (USM) has the advantages of low speed and high torque, no interference from electromagnetic field, power off self-locking and so on. However, due to the special operating mechanism based on friction, the operating state of ultrasonic motor has obvious nonlinear characteristics. Therefore, the traditional analytical method is too complicated to construct the mathematical model of USM. In this paper, the second order model of USM is established by using system identification method based on Hammerstein model. In order to improve the speed stability of the USM, to overcome the speed fluctuations caused by temperature changes and frequency changes, the sliding mode control algorithm is applied to the design of the controller to improve the speed regulation performance and operation robustness of the USM. The control algorithm is designed based on the second-order mathematical model of the motor, and the robustness of the sliding mode control algorithm is verified by simulation. Design experiment based on DSP TMS320F28069 to observe the speed regulation performance of the proposed control algorithm. Experiments show that the algorithm has good control effect.

In capacitor energy storage pulsed power supplies, it is common to use a pulse inductor to adjust the discharge current waveform. To avoid magnetic saturation, hollow copper windings are typically employed for the pulse inductor. In this study, we utilized copper foil as the base material and adopted an epoxy casting method to manufacture an 80 μH pulse inductor. However, during experimentation, when the test current amplitude reached 45 kA, the pulse inductor suffered severe damage with the electrodes and epoxy core being detached, and the detachment area was heavily burnt. Through analysis, it was determined that the main causes of these issues were the inadequate design of the copper windings and electrode structure, as well as insufficient strength in the epoxy casting structure. To address these problems, we improved the epoxy core, copper windings and electrode structure, and fabricated an improved inductor by using epoxy glass around the copper windings. The improved inductor performed well without any abnormal occurrences under a pulsed current of 51 kA. This development process holds practical value for the research on pulsed power supplies.

Dynamic Line Rating (DLR) holds significant importance in fully tapping transmission potential of overhead transmission line and mitigating power shortage challenges compared to Static Line Rating (SLR). However, existing interval prediction methods based on affine arithmetic for DLR exhibit limitations such as excessively conservative prediction intervals and high computational burden. In order to tackle these challenges, the multiplication and division operations of affine arithmetic are improved by reducing the quadratic terms and introducing the interval Taylor formula in this paper. Based on these improvements, an interval prediction method for DLR is proposed by using the improved affine arithmetic. Finally, the computed results of the improved affine arithmetic, traditional affine arithmetic, and Monte Carlo algorithm are compared to validate the accuracy and practicality of the proposed method.

The possibility of strong electromagnetic radiation caused by lightning waves invading substations has always been a concern. This article aims to introduce an accurate calculation method for evaluating the radiation field generated after lightning waves invade substations. This method combines the theory of traveling wave antennas and the theory of electromagnetic wave refraction and reflection, and can accurately analyze and predict the distribution and intensity of the radiation field. By deeply understanding the physical mechanism and mathematical model of lightning wave intrusion into substations, we can better address this challenge and ensure the safe operation of substations.

To obtain the accurate motor position and speed feedback information, this paper presents a new position and speed measurement method of segmented long primary double-sided linear motor (SLP-DSLM). Considering that the SLP-DSLM has a double-sided long primary and dynamic secondary structure, a grating sensor based on laser array to measure the position is used in this paper firstly. Then, a new position acquisition method based on polynomial fitting is proposed in this paper. Finally, the adaptive tracking differentiator (TD) is introduced to obtain the velocity of secondary. Compared with the conventional position accumulation method, the hardware-in-the-loop experiment proves the effectiveness of the proposed method.

The operation quality of low-voltage current transformer directly affects the accuracy of electric energy measurement. This topic analyzes the metering performance of low-voltage current transformers in long-term operation, puts forward targeted optimization management suggestions, and guides the research on lean management optimization of low-voltage current transformers.This topic first investigates the characteristics of low-voltage current transformers that have been in operation for a long time. After that, this topic focuses on the research on the spot check of low-voltage current transformers, establishes a sampling plan based on Stratified sampling, completes the spot check analysis of 599 low-voltage current transformers, and analyzes and summarizes the influence law of multiple factors such as the unified recruitment mode, operating years, test current, transformation ratio, etc. on the measurement performance change of long-term operating low-voltage current transformers. At the same time, the targeted guiding opinions on the research of lean management optimization of low-voltage current transformers are proposed.

Traditional voltage transformers often encounter problems such as large size, insulation damage, and core saturation. Voltage sensors based on the electric field coupling principle avoid these problems. In early research, the method of changing the mutual capacitance between differential electrodes had many problems and was difficult to apply in practice. This study uses multilayer ceramic capacitors to replace mutual capacitance to create a new voltage sensor. Tests have shown that the sensor has excellent linearity and phase accuracy, and performs superiorly in high-frequency response. In addition, it offers the advantages of cost-effectiveness, compactness, shape adaptability, and easily adjustable voltage divider ratio.

Gas detection is an effective early warning method of thermal runaway of lithium-ion battery (LIB). This paper proposes a method for in-situ detection of LIB thermal runaway gases based on Raman spectroscopy. Firstly, the detection platform is developed and the limit of detection (LOD) is obtained. According to the LOD, the sensitivity of gas Raman spectroscopy detection is significantly improved by fiber-enhanced technology. Next, a thermal runaway monitored by the platform is performed. Benefiting from the unique advantage of simultaneous and non-destructive analysis of Raman spectroscopy, real-time and in-situ detection of multiple gases generated during LIB thermal runaway is realized. A warning time of 526 s is achieved by the detection of CO2 in the early stage of thermal runaway, which provides sufficient time for battery safety management as well as personnel evacuation, and demonstrates the potential of gas Raman spectroscopy detection in LIB thermal runaway gas analysis and fault warning.

Presently, most of the ramp-type gravity energy storage devices through transport heavy blocks between the upper and lower stacking yards to switch between energy storage and energy release, but this method cannot regulate the energy output by changing the number of heavy blocks released in time, so it is difficult to quickly and accurately respond to the demand of the load, and it causes additional energy loss as the load demand changes. In this paper, we add auxiliary heavy block stacking yard on both sides of the ramp channel, and by controlling the release quantity of heavy blocks in the top stacking yard, selecting different heights of the ramp stacking yard to release the heavy blocks, and controlling the position of the grasping heavy blocks in the ramp stacking yard, we realize the precise control of the output energy of the gravity storage device, which improves the response speed of the gravity storage device and reduces the extra energy loss. Finally, based on Matlab/Simulink simulation, the correctness and effectiveness of the proposed method are verified.

The contact resistance of GIS contacts is related to the stable operation of the power system. In this paper, a GIS contact resistance measurement device based on the pulse current method is developed on the FPGA platform, which accurately measures the time-domain curve of contact resistance by compensating for the influence of inductance, which is of positive significance for further evaluating the contact contact state.

With the advancement of new energy storage technologies and their widespread industrial applications, the issue of thermal runaway in lithium battery energy storage systems has become increasingly significant. Thermal runaway in energy storage systems can not only result in equipment damage and extended downtime but also pose serious threats to personnel safety and the environment. Therefore, early warning of thermal runaway in energy storage systems has gained paramount importance and has garnered extensive research attention among domestic scholars. However, conventional methods for thermal runaway prediction primarily rely on empirical models, lacking a comprehensive analysis and profound understanding of operational data from energy storage systems. Data-driven approaches offer a fresh perspective on thermal runaway prediction, enabling the identification of potential risk factors from extensive historical data and providing accurate warning and prevention strategies. This paper first introduces the principles and methods of data-driven algorithms, while exploring how abundant historical data can be utilized to identify latent thermal runaway risk factors. A comparison with traditional warning methods is also provided, demonstrating that the approach proposed in this paper outperforms in terms of false alarms and missed warnings. Finally, the paper discusses the potential challenges and future directions in proactively addressing thermal runaway risks through data-driven prevention.

With the rapid development of national industry, the demand for power energy in all walks of life is increasing, which poses a major challenge and huge demand for the safe and stable operation of the power system. 550 kV/8000 A combined electrical appliances are representative of large-capacity power switchgear in the power system. The safe and stable operation of GIS is the key to the normal operation of power system. It is of practical significance to study the thermal distribution characteristics of GIS for improving the reliability and security of power system. This paper establishes an electromagnetic thermal coupling model for 550 kV/8000 A combined electrical appliance. Through multi-physical field coupling, electromagnetic loss is calculated and input into the thermal field as a load to calculate the temperature distribution. The results show that the contact resistance between the highest point of temperature rise and the intermediate conductor and the contact base is in line with the national standard, which provides a reference for the future optimization design of the product.

With the high-proportioned distributed PV supply connected to the distribution network, the voltage quality problem is particularly prominent. Firstly, a reactive voltage optimization model based on distributed PV reactive voltage regulation capability is established to improve the voltage quality by using PV reactive voltage regulation capability. At the same time, considering that the VVO model is nonlinear non-convex optimization model, the direct solution of the heuristic algorithm takes a long time, which is not conducive to the online VVO. In this regard, the SA algorithm is applied to obtain the distributed PV optimal output data set, and then the XGBoost model is trained according to the distributed PV optimal output data set, and the VVO of the distribution network is realized from the data-driven perspective, which significantly improves the solving speed of the distribution network optimization model. Finally, a typical distribution network example of IEEE 33 nodes is used to analyze the rationality of the proposed method.

The national holiday policy has a significant impact on the holiday load, and the curve's shape differs from the regular daily load, making it challenging to directly anticipate the overall load. The categorization predicting approach presented in this research is based on the division of regular days and holidays. First, the load is divided depending on the date variable after an analysis of the characteristics of an ordinary day and a holiday load. The combined model based on similar day selection and generalized regression network is then utilized to forecast in accordance with the usual daily load. In order to predict the holiday load, a fusion model based on LightGBM and XGBoost is used. The experimental results demonstrate, using the data set provided by a power supply bureau in southern China as a practical example, that the classification forecasting method put out in this study increases the precision of global load forecasting.

In electromagnetic launch systems, the sliding electrical contact formed by the armature and the rail poses challenges to track heat management research due to ultra-high-speed friction. To investigate the serious impact of armature-rail overheating under high-speed sliding electrical contact on the launch performance and service life of the launch system, researchers have established a transient simulation model of armature-rail launch system high-speed sliding electrical contact based on finite element analysis software. This model takes into account both the frictional heat and the Joule heat effect generated by contact resistance between the armature and the rail. Researchers have analyzed the current density, heating power, and temperature distribution between the armature and rail in the linear propulsion system and compared these data with the actual abrasion and burn conditions of the armature and rail obtained from actual launch experiments. Through these comparisons, researchers have identified the distribution rules of current density and temperature in the armature-rail launch system before and after the separation of the armature and rail, verifying the effectiveness of the simulation model. This study provides theoretical support for the subsequent modification design of armature materials and the preparation of abrasion-resistant materials.

To enhance the inertia and damping of power grid, enhance the support ability of voltage and frequency, virtual synchronous generator (VSG) technology is widely applied. An improved pre-synchronous grid connection strategy is proposed to address the issues of large power oscillations and current surges during VSG off grid switching. Under the coordinate αβ axis, a method similar to reactive power calculation is used to obtain the adjustment amount of VSG output voltage, and through control, fast and accurate synchronization with grid voltage is obtained to achieve smooth switching of VSG off grid. Finally, the effectiveness of the proposed improved pre-synchronization grid connection strategy is verified through simulation and a 50 kV/A prototype is built to prove the feasibility of proposed method.

In order to solve the manufacturing, transportation, installation and repair problems of the giant fan, on the basis of the traditional one-piece dual-rotor induction machine, the two rotors of the fractional-slot centrally wound dual-rotor induction machine (15-slot 7-pair poles versus 24-slot 11-pair poles) are modularized separately, and the use of the T-type modular structure, which is equivalent to inserting a rotor gap in the yoke part of the rotor, thus changing the rotor magnetic circuit. According to the machine principle of this machine, the analytical method is used to derive the winding coefficients of the rotor for the T-type modular structure, and it is analytically obtained that the modular rotor structure reduces the amplitude of the winding coefficients of the non-operating subharmonics to a certain extent, and reduces the amplitude of the air-gap magnetism of the non-operating subharmonics. And through the finite element analysis on the traditional dual-rotor induction machine and modular dual-rotor induction machine no-load and load simulation, the results of comparative analysis, theoretical analysis and simulation results basically match. The modular rotor structure effectively improves the performance of the machine and increases the operating efficiency of the machine.

With the aim of double carbon in China, the incorporation of a significant quantity of novel energy devices and dynamic compensation devices and dynamic compensation devices into the grid has caused many instances of sub-synchronous oscillation (SSO) incidents, which have a considerable impact on the secure and stable operation of the power system. Rapid identification of SSO parameters can provide characteristic parameters for suppression measures, real-time warning, and analysis of SSO. Therefore, this paper proposes a time-frequency analysis approach based on the Short-Time Fourier Transform (STFT) and incorporates it with the Sparse Time Domain (STD) technique for the identification of sub-synchronous oscillation parameters. The proposed method first applies the SST time-frequency domain transformation to the oscillation data collected by Phasor Measurement Unit (PMU) at key nodes in the power grid, decomposing a set of signals with multiple modes into different modal components. Subsequently, an improved ridge extraction method is employed to reconstruct the time-frequency domain signals of each mode. The STD method is subsequently employed to precisely identify the modal parameters of SSO. Finally, through the analysis and verification of ideal examples and real-world power grid data, the identification results demonstrate the accuracy, robustness, and computational efficiency of the proposed method, thus satisfying practical engineering applications.

In response to the problem of low fault identification rate of induction motor, An induction motor fault diagnosis method based on the combination of fast overall average empirical modal decomposition (FEEMD) and support vector machine (SSA-SVM) optimized by sparrow search algorithm is proposed. First, the stator current is decomposed into intrinsic modal components (IMFs) of sequentially decreasing frequency by FEEMD, and then the IMF components with larger correlation coefficients are selected by correlation coefficient method and the energy entropy and sample entropy are calculated as the eigenvectors, which are then inputted into the SSA-SVM model in order to receive the diagnosis results. The results show that the fault diagnosis accuracy of SSA-SVM model reaches 96.7%, which has higher accuracy and shorter time compared with the two models of Grey Wolf Algorithm (GWO) optimized SVM and Particle Swarm Algorithm (PSO) optimized SVM, which verifies that the method is a reliable method for fault diagnosis of induction motors.

In recent years, the frequent occurrence of high-voltage cable buffer layer ablation faults seriously threatens the safe and stable operation of the power system. In order to eliminate the hidden danger of high-voltage cable ablation, a kind of buffer layer ablation fault repair liquid with acrylic resin as the matrix was designed in this paper. The influence of the repair liquid on the electrochemical corrosion of aluminum sheath was analyzed, and the application performance of the repair liquid was tested. The results shown that the repair liquid prepared with acrylic resin as the matrix, ethyl acetate as the solvent, and carbon black as the conductive filler adhered well to the buffer layer. In addition, the repair liquid formed an acrylic resin-carbon black coating in the ablative buffer layer. The corrosion current density of aluminum in the mixed liquid of water-blocking powder and acrylic resin was about 9.72 × 10–4 μA/cm2. Therefore, the acrylic-based repair liquid did not cause new electrochemical corrosion problems in a short time after injection into the cable. The repair liquid, at low viscosity, was able to reduce the volume resistivity of the ablative buffer layer, and cured quickly at a certain temperature by evaporating. The study provided a reference for the repair of high voltage cable ablation fault.

In order to solve the problems of traditional image processing algorithms in handling precise target detection and condition monitoring of power cable, this paper proposes an improved infrared image-based condition diagnosis scenario of power cable based on Mask R-CNN and BP joint algorithm. Mask R-CNN is used to solve the problem of refined image segmentation when the background of cable infrared image is complex. And BP neural network algorithm is used to classify and identify the key features of power cable. The results show that the proposed method has a good detection effect on the operation status of cables in infrared images with an average accuracy rate of 87.63%, which presents a good solution to the problem of infrared image identification of substation equipment and its status assessment.

With the increasing application of computers, various analog signals (such as fire alarm/cabin door/fuel volume/control valve, etc.) need to be collected and calculated in the field of electromechanical control of aircraft. The conditioning circuit in these signal acquisition circuits is essential, and a large number of high-speed or low-speed amplifiers are used in the conditioning circuit. The stability of the amplifier determines whether the signal acquisition is stable, reliable, and accurate, Therefore, the stability analysis of amplifiers, as well as the gain and noise figure, are necessary factors to consider in the design of amplifier conditioning circuits. Based on these factors, an amplifier that can work stably and reliably in various harsh environments, such as gain, bandwidth, and noise, can be designed, truly reflecting the real-time changes of the input signal in the previous stage.

Aiming at improving the torque performance of the external rotor synchronous reluctance machine, this paper establishes a mixed surrogate model on the basis of analyzing various design parameters and performing multi-objective optimization. Firstly, the influence of parameters on the average electromagnetic torque and torque ripple ratio of the machine is analyzed. In order to improve the prediction accuracy and stability, shorten the optimization cycle, a novel mixed surrogate model based on the Kriging model and RBF model is proposed, the global accuracy and local accuracy of the model are verified, the addition criterion based on the dynamic dimension search algorithm is designed to improve the accuracy of the model, a dual optimization framework of constructing the surrogate model-optimizing model accuracy-optimizing torque characteristics is built, finally the electromagnetic torque and torque ripple ratio of the machine are optimized. The results show that the average torque and torque ripple ratio of the optimized external rotor synchronous reluctance machine are significantly improved compared with the initial design.

The fault of the shunt capacitor device in a 220 kV substation led to the 66 kV bus outage and the total shutdown of six 66 kV substations. In order to find out the specific cause of the fault and avoid the recurrence of similar problems, analysts conducted a comprehensive analysis and judgment on the capacitor fault process and causes from various aspects such as protection action, setting calculation, disassembly inspection and harmonics. Through analysis, it is determined that the reason for the expansion of the accident is the mismatch between the shunt capacitor bank unbalance protection current transformer and the protection device. In view of this accident, the corresponding measures and suggestions are put forward from the aspects of optimization protection setting principle, bridge difference current transformer transformation, etc., which is of great significance to improve the operation reliability of this type of shunt capacitor device.

In order to address the large amount of data interaction during high-speed train operation and the high reliability of data security, this paper designs a new type of security system based on FPGA+DSP as the main framework. The system adopts XINIF parallel interface in DSP to achieve interconnection with FPGA, which accelerates the data transmission speed. At the same time, on the base of the original double 2-vote-2, two-way redundancy system is added to improve the safety and reliability of the computer interlocking system. Analysed by simulation experiments, the new safety system has a certain degree of improvement in reliability and safety compared with the traditional double 2-vote-2 system.

In the new power system, the harmonic source and the content increase, which puts forward a new test to the oil-impregnated paper insulation performance of the transformer. Therefore, this paper carries out the research on the effect of harmonic voltage on oil-impregnated Paper insulation partial discharge (PD) by means of the partial discharge platform under the action of harmonic voltage, and analyses the influence law of harmonic voltage frequency on partial discharge parameters. The results show that the harmonic voltage changes the partial discharge inception situation for the oil-impregnated paper due to the differences in harmonic polarity at different frequencies from the 50 Hz-industrial voltage. The split-peak phenomenon appears in all of the PD patterns of the oil-impregnated paper under the action of harmonic voltages and it is more obvious in the higher harmonic frequency. The harmonic voltage causes the maximum and average discharge magnitude increases, whereas the number of discharge pulses and discharge repetition rate decreased under the positive and negative discharge.

The high frequency power transformer faces some problems such as partial discharge and premature insulation failure due to the effect of electrothermal coupling stress. In order to study the coupling effect of ambient temperature and humidity on the characteristics of polyimide partial discharge, this paper studied the characteristics of polyimide partial discharge at four temperature points of 75–150 ℃ and three humidity points of 40–80%. The initial partial discharge voltage, the maximum and average discharge amplitude and characteristic parameters were counted to observe the surface morphology. The test results show that temperature is proportional to the maximum discharge amplitude, humidity is proportional to the maximum discharge amplitude when the temperature is less than 100 ℃, and the maximum discharge amplitude increases first and then decreases when the temperature is greater than 100 ℃. For the average discharge amplitude and the number of discharge per unit time, with the increase of temperature, the first increase and then decrease, the temperature is less than 100 ℃ and the humidity is less than 60%, the temperature is more than 100 ℃ and the humidity is more than 60%, and the temperature is more dominant.

The stator laminations of large permanent magnet synchronous wind generators are often sectionalized and overlapped, which will cause the magnetic circuit asymmetry. The resulting asymmetric magnetic flux around the shaft yields intrinsic shaft voltage along the shaft. The shaft voltage will cause electric corrosion of the bearing and endanger the security of system. In this paper, the shaft voltage of a 5.57 MW permanent magnet synchronous wind generator with sectionalized and overlapped stator laminations is calculated through analytical method and finite element method. The results show that when the number of overlapped layers is the same, the voltage amplitude with symmetrical overlapping is much smaller than that of asymmetrical overlapping. It is necessary to properly match the sectionalized stator and the number of overlapped layers combination. In a certain range, the larger the rotating speed, the larger the shaft voltage amplitude; The shaft voltage amplitude of the generator under loaded condition is larger than that under no-loaded condition.

Due to the development of new power systems, the impact of stochastic loads, demand response participation, distributed voltage randomness and volatility and the variety of measurement devices lead to the complexity of the distribution network structure and the aggravation of the state estimation task, which may lead to a decrease in the estimation accuracy of the dynamic state estimation algorithm in some scenarios. In this paper, the dynamic state estimation method for distribution networks based on improved H∞ volumetric Kalman filtering is firstly combined with volumetric Kalman filtering and H∞ filtering to robust the model error uncertainty problem, and then finally combined with a noise valuer to estimate the parameters in the process noise online and to reduce the impact of noise on the prediction error. Simulations are carried out by the IEEE69-node system, and the results show that the method maintains a relatively high estimation accuracy under normal system operation, after the demand response is involved in peak shaving, and when the load undergoes sudden changes.

Bearing fault detection based on stator current signals has the characteristics of non-invasive and easy to implement, but weak fault features are submerged by strong background noise, posing a great challenge. Although adaptive chirp-mode decomposition (ACMD) has achieved good results in processing non-stationary signals in many fields, it requires some prior information to initiate, which limits its widespread application. Therefore, an improved ACMD method is proposed. First, the instantaneous frequency of initial estimation is obtained based on general linear chirplet transform. Then, the instantaneous frequency is used as the iterative condition, and the motor current signal will be decomposed into several modes. Finally, use power spectrum analysis to determine if it is faulty. The experimental results indicate that the improved method proposed in this paper is feasible for bearing fault detection.

The stator current of induction motor is not affected by environmental interference, so it is widely used in the motor bearing fault detection. But weaker fault features are easily masked by strong noise, and are difficult to detect. Therefore, an improved adaptive local iterative filtering fault detection method is proposed. Aiming at the problem of poor noise reduction effect of adaptive local iterative filtering, a method for screening data is proposed, which solves the problem of excessive noise components, and improves the accuracy of fault identification. Experimental results show that the proposed method is very effective for bearing fault detection and has better performance than the original method.

When the induction motor bearing fails, the stator current signal not only has weak fault features related to fault information, but also includes plenty of strong background noise, which increases the difficulty of fault detection. In order to effectively extract the fault features, this paper proposes a multi-parameter optimized resonance sparse signal decomposition (RSSD). The proposed method does not depend on frequency range, but divides the spectrum through resonance, and overcomes the limitation of traditional RSSD methods that rely on manual experience to set important parameters such as quality factors. The novelty of this method lies in the introduction of gorilla troops optimizer (GTO) algorithm to automatically select quality factor Q, weight factor A and Lagrange multiplier $$\mu $$ μ . Firstly, with the minimum fitness function as the goal, GTO is used to optimize the selected parameters. Secondly, RSSD is used to obtain the best resonance component and power spectral density (PSD) carried out to extract the bearing fault feature frequency. The experimental results show that the proposed method is more effective in detecting bearing faults than the traditional method.

To resolve the issue of lithium-ion batteries in electromagnetic emission work environments experiencing voltage drop at the battery output due to high rate discharge, which in turn cannot meet the DC voltage requirements of the load converter. Therefore, this article proposes an N+1 level dynamic chopping structure energy storage system topology to compensate and stabilize the DC bus voltage. Meanwhile, in order to improve DC bus voltage compensation performance, this paper adopts a composite compensation control strategy of LADRC+PI. In response to the problem of negative saturation caused by initial feedback in the LADRC controller, this article uses the method to start the observer feedback by judging the DC bus voltage and the reference voltage. Secondly, in order to reduce the three fold fundamental frequency ripple on the DC side caused by the modulation strategy of the load inverter, the bus voltage feedback value filtered by a notch filter is used for feedback to suppress the DC side current ripple. Finally, the above strategies were validated through the RT-LAB experimental platform.

Electric ducted fans are widely used in hybrid aircraft, electric aircraft, and VTOL vehicles. The future development of ducted fans will focus on achieving high power density, higher cruise speeds, longer battery life, and increased task load capacity. Under the conditions of specified tension and motor power constraints, the ratio of hub to blade tip and the ratio of inner and outer diameters of the motor stator are introduced to analyze the performance of the propulsion system in this paper. And this article mainly studies the relationship between the static thrust of the fan, motor power, and motor temperature rise, and proposes the direction for optimizing the design of duct fans based on the relationship between these three factors.

Fast and stable tracking of reference signals for each branch is an essential indicator for the output current control of a parallel H-bridge power supply system. Due to parallel structure of multiple inverters used in parallel H-bridge power supply, inconsistent output voltage parameters and line impedance coefficients for each branch can lead to circulating current effects. Excessive circulating current will lead to poor tracking stability for branch current. In response to circulating current problem for parallel branches of parallel H-bridge power supply, the causes of circulating current in parallel branches are analyzed, and the role of current sharing reactor in suppressing circulating current is studied, as well as the corresponding relationship for parameters of current sharing reactor and circulating current. A calculation method for electrical parameters based on current sharing reactors is proposed based on operating effects of parallel H-bridge power supply systems under different current sharing reactors are simulated and experimentally verified. The results verified that the proposed design method for current sharing reactors has good reliability and practicality.

For maintaining the stable operation of power systems, there is an urgent need to master the electro-thermal characteristics of DC cables. This paper establishes a three-dimensional electric-thermal coupling simulation model of 220 kV cable terminals, and simulates three kinds of operating conditions (no defects, small amount of water intake, and large amount of water intake) of the cable terminals respectively. Based on the simulation results, the electrical-thermal characteristics of cable terminals under defects are analyzed and summarized. The results show that the water ingress defects mainly affect the localized electrical and thermal characteristics of the cable terminal, with less influence on the overall affectivity. Slight increase in average temperature in the area around the defect, accompanied by a distorted electric field with a higher field strength (10% increase for small amounts of water intake, 15% increase for large amounts of water intake). The results of this paper can provide a reference for temperature rise phenomena and insulation design of DC cable terminals.

This research suggests an electric load forecasting method that takes into account the marginal price of electricity in order to further increase the forecasting accuracy for electric loads. By including the marginal electricity price, the approach creates the training and test sets for the electric load. The establishment of an electric load prediction model using a Wavelet Neural Network (WNN) is followed by load prediction using the local power grid's current data. By comparing the evaluation indicators with the electric load forecasting case without considering the marginal electricity prices of nodes, the results show that considering marginal electricity prices can improve the accuracy of electric load forecasting.

The structure of valve hall fittings in UHV DC converter station directly affects the reliability and stability of each system in the converter station, surface defects will inevitably occur in the process of processing, transportation and installation of large size fittings, and the existence of these surface defects will reduce the switching impulse voltage of air gap. In this paper, the simulation model of shielding ball with three kinds of surface defects including screw protrusion, burr and scratch under ±800 kV and ±1100 kV is established, and the influence law of different defects on the surface electric field of shielding ball is analyzed.

In this study, a fault diagnosis method for power transformers based on dissolved gas analysis (DGA) was proposed. Firstly, nuclear principal component analysis (KPCA) is used to preprocess the collected fault data to remove the interference data, and KPCA is used to perform feature extraction on the mixed DGA data. Then, the dung beetle optimization algorithm (DBO) was used to optimize the neural network algorithm (BP), and an improved dung beetle optimization algorithm (DBOBP) was formed to achieve better optimization accuracy and convergence speed. Since tent diagrams are used instead of traditional population initialization methods, this method improves population diversity. Simulation examples verify the superior performance of the proposed method, including high diagnostic accuracy, short diagnosis time, strong significance and effectiveness. This study provides a feasible research idea for solving practical engineering problems in the field of power transformer fault diagnosis.

Virtual synchronous generator (VSG) control technology is widely used in off-grid control of distributed power supply by simulating the characteristics of synchronous generator, increasing the inertia of the system, realizing the advantages of frequency regulation and voltage regulation. In the multi-VSGs islanded operating system, the damping function of VSG can play a role of primary frequency modulation similar to droop control. The load increment is distributed according to the damping coefficient. When the system frequency crosses the line due to sudden load change, the droop characteristic can be changed to bring the system’s frequency back to the normal range. The secondary frequency modulation characteristics of translation droop curve method and changing damping coefficient method are analyzed, and a joint adjustment method combining translation droop curve and changing damping coefficient is proposed. Finally, simulation experiments are carried out on Matlab/Simulink platform to verify the effectiveness of the proposed method.

Overcharging and runaway of lithium batteries is a highly challenging safety issue in lithium battery energy storage systems. Choosing appropriate early warning signals and appropriate warning schemes is an important direction to solve this problem. This research proposes a battery overcharge warning scheme based on the hard case lithium battery explosion proof valve Strain gauge. Starting from the external strain mechanism of the lithium battery, the strain change of the lithium battery explosion proof valve under normal conditions and overcharge is studied. Based on the comparison of the two conditions, an online warning scheme using sliding window and data standard deviation is proposed. The experimental results show that: (1) under normal charging and discharging conditions, the strain of the safety valve of the lithium battery will monotonically increase with the increase of SOC and battery temperature; (2) Under overcharging conditions, the inflection point of the strain change of the explosion-proof valve occurs earlier than the characteristic gas, at most about 600 s earlier; (3) The online warning method using sliding windows and data standard deviation can advance the warning of characteristic gases by about 500 s and improve the generalization ability of the method. This study proposes a cheap and reliable early warning scheme for lithium battery energy storage systems, greatly improving the safety of battery systems.

During the launch of electromagnetic railguns, the deformation of high strain rate materials in armature and orbit will affect the orbital launch performance, and it is of great significance to study the instability mechanism of electromagnetic energy materials under high strain rate. This paper presents a novel approach for evaluating the high-speed behavior of metallic materials through the utilization of magnetic pulse drive. The proposed method involves employing the magnetic pressure generated by the magnetic pulse driver (MPD) to apply stress input pulses, enabling uniaxial tensile deformation of the material. To measure the stress-strain relationship of the specimen, the study utilizes high-speed cameras and digital image correlation (DIC) systems. High-speed cameras and digital image (DIC) systems are used to measure the stress-strain relationship of the specimen. At the same time, by establishing a finite element model, it was found that the strain rate can reach 2000 s−1 within a short time and maintain relative stability. Additionally, a tensile experiment was carried out under a charging voltage of 35 kV. The results demonstrated great consistency between the calculation results and the experimental values, which confirming the effectiveness of the proposed method.

Low voltage multi-terminal DC system is one of the important forms of future power grids, and its commonly used control method is droop control. This article proposes a variable droop control mode based on traditional droop control and applies it to low voltage multi-terminal DC systems. Variable droop control has a larger operating boundary and better stability compared to traditional droop control. Similar to traditional droop control, the variable droop control strategy and key system parameters are closely related to the small signal stability of the system. In order to verify the stability of low voltage multi-terminal DC system based on variable droop control, this paper constructs a Small-signal model of low voltage multi-terminal DC system based on variable droop control, and uses the analysis method of dominant eigenvalue to study its stability and operating boundary. Validate through Matlab/Simulink simulation models, and compare the low voltage multi-terminal DC system based on variable droop with the low voltage multi-terminal DC system based on traditional droop. The results indicate that the variable droop control proposed in this paper has higher stability compared to traditional droop control.

In order to achieve high thrust density and dynamic performance, this study investigates design criteria and electromagnetic characteristics of a permanent magnet (PM) synchronous linear motor with star-delta winding. Firstly, analytical model of armature magnetic potential harmonics and winding inductance is established. Next, electromagnetic characteristics are calculated by finite element method. Simultaneously, inductance waveform characteristics considering end effects with different pole-slot combinations are analyzed respectively, and then design criteria for hybrid windings are summarized. Finally, experiment of 14-pole, 12-slot linear motor is carried out to validate analysis results.

In order to meet the urgent needs of high-reliability portable plasma generators in many fields, this paper designs a portable atmospheric pressure air discharge plasma generator and tests its discharge performance. By using a high-voltage package to amplify the low-voltage pulse generated by the micro-arc lighter, and then multi-stage amplification by the voltage-doubling rectifier circuit, a high-voltage pulse generator with low input, high output, compact structure and repeatable charging is realized, which can effectively break through the air to form a blue-purple plasma arc. The purpose of this paper is to provide a convenient and rechargeable plasma generation scheme, which is oriented to industrial applications and can meet the needs of plasma applications in material insulation detection, short-time discharge, confined space discharge and other occasions.

For the purpose of addressing the issue that the maximum power point tracking (MPPT) perturbation method of observation cannot realize both speed and accuracy, an improved perturbation observation method based on duty cycle is proposed in this paper, which tracks the maximum power point more quickly and accurately through the optimization of step size. It is minutely introduced the principle and implementation process of the revised algorithm and the viability of the proposed method can be seen from the simulation results. The improved disturbance observation method based on duty cycle can obviously have higher tracking accuracy than the traditional disturbance observation method on the basis of ensuring the tracking speed of the maximum power point, and can play a better role in ensuring the stability, accuracy and rapidity of the system, and achieve better results.

Sand weather often occurs in areas with an altitude of 3500 m, which affects the insulation character curve of transmission line gaps. Therefore, so as to investigate the impact of sand on the typical gap discharge character curve of rod and rod plane in high-altitude areas, gap discharge tests were conducted using a simulated wind and sand test device at an altitude of 3500 m in Nachitai under DC voltage conditions. The single variable method was used to obtain the impact of different wind speeds, sand grain charges, and sand grain sizes on the discharge character curve. The results show that in a high altitude area of 3500 m, the effect of sand parameters, including wind and sand conditions, wind speed, sand grain charge, and sand grain size, on the DC discharge voltage of typical gaps between rods and planes is within 3.2%.

Tower cranes, excavators and other external damage hazards lead to frequent transmission channel accidents. Effectively detecting the external damage hazards around the transmission channel is of great significance to ensure the safe and stable operation of the transmission line. Therefore, based on the edge intelligent chip, an intelligent edge detection device for the hidden danger of transmission channel is developed, and a lightweight hidden danger identification method suitable for the front-end device with limited computing resources is proposed. Firstly, the visual feature of the transmission channel image is extracted by using the depth residual network, and then the candidate area of the hidden danger target is captured by using the candidate area production network RPN, Then the full convolution neural network FCN is used to classify and locate the hidden danger of external damage. Finally, the actual collected transmission channel images are constructed into a sample set for model test and experimental verification. The experimental results show that the proposed method shows good applicability in the edge device.

In order to rapidly optimize the current waveform quality and the projectile velocity of the electromagnetic launch system, the multiphase trigger angle optimization problem of the pulsed alternator is simplified based on the two-dimensional finite element analysis and circuit co-simulation, and the corresponding equivalent circuit model is established. Based on the splitting process of armature winding, three kinds of trigger angle optimization strategies are proposed, which are equivalent two-phase, equivalent four-phase and full eight-phase. Based on the equivalent circuit, aiming to obtain the best current waveform quality and the maximum projectile velocity of the electromagnetic launch system, three trigger angle optimization strategies are optimized by using multi-objective genetic algorithm. Among the Pareto frontier points obtained by the three optimization strategies, the points with similar projectile velocity are selected as the optimization results, and the results show that they have similar output characteristics, which verifies the effectiveness of the three trigger angle optimization strategies. At the same time, the trigger angle optimization strategy can be extended to the pulsed alternator with similar armature winding characteristics, which has certain reference significance for the optimization of pulsed alternator.

During the actual operation of composite insulators, they may be affected by various deterioration factors. Acid generated by partial discharge and abnormal heating may accelerate the deterioration of ECR glass fibers in composite insulators, leading to decay-like fracture of composite insulators. In this article, the deterioration experiment of ECR glass fibers comprehensively considered the effects of acid and temperature. The acid heat deterioration experiment of ECR glass fibers were conducted to investigate the changes in morphology and mechanical properties of ECR glass fibers. The results showed that the degradation effect of acid solution on ECR glass fibers was not significant at room temperature, while the surface of ECR glass fibers deteriorated by acid heat became rough and a large amount of powdery debris appeared; Meanwhile, compared to nitric acid, oxalic acid has a more severe degradation effect on glass fibers. After 12 days of deterioration with 1mol/L oxalic acid at 80 ℃, the tensile strength and elastic modulus of glass fibers decrease by more than 90%; After acid heat degradation, there are a large number of “debris” on the surface of the glass fiber. Fiber damage and fracture phenomena occur at the same time.

At present, it is common to use external ultrasonic sensor and built-in UHF sensor to detect the partial discharge signal in GIS. The defects of this technology are the single function of the sensor, the low accuracy of the local discharge detection, and the sensor cannot fit the GIS equipment shell well. Based on the principle of partial discharge, an external ultrasound-UHF integrated sensor based on polyvinylidene fluoride (PVDF) is designed, which can simultaneously receive and output ultrasonic and UHF signals generated by partial discharge. The optimal parameters of the integrated sensor were obtained from simulations, which were proved to satisfy the national standard. The research in this paper effectively solves the problem that the two signals cannot be output simultaneously when the two kinds of sensors are installed separately, realizes the simple and reliable judgment of the location of the partial discharge.

Under the “double carbon” policy and the development of distributed energies, microgrids using photovoltaic-battery energy storage systems have encountered rapid development. The photovoltaic battery system not only improves the hosting capacity of renewable energy and local consumption rate but also ensures stable power supply through the electricity market by charging and discharging the battery storage system in the distribution network. In this paper, a target model, which considers the constraints of grid voltage, power balance, environmental benefit, operating cost of energy storage configuration, and line loss, is established. An improved particle swarm optimization algorithm is proposed to optimize this target model. Through the proposed algorithm, the configuration scheme of the energy storage system, the scheduling scheme, and the operation cost of the energy storage system on typical days in different seasons are obtained. The simulation results have shown that the proposed algorithm can solve the problem of microgrid location and energy storage system configuration, can reduce the line loss while taking into account economic benefits, can promote the consumption of renewable energy, and can give the scheduling model of different seasons.

This paper focuses on the issue of amplitude deviation and constant offset in the motor winding currents, which are caused by non-ideal factors such as variations in device parameters and changes in device parameters during the lifetime in the linear drive circuit of a three-phase open-winding permanent magnet synchronous motor (OW-PMSM). The influence of unbalanced three-phase current on motor torque and speed is studied. By deriving the effect of the deviation amount on the dq0 axis currents based on the mathematical model of OW-PMSM, the analysis further examines the effect on output electromagnetic torque. A closed-loop simulation system for the linear drive of OW-PMSM is developed using PSIM simulation software to verify the influence of unbalanced current on the closed-loop control system and analyzes the simulation results. These findings provide valuable insights for practical applications of linear drive system and future research on three-phase OW-PMSM.

The degradation process of Ultra high frequency PD sensors is complicated and random due to the harsh distribution station scenario. The reliability research of Ultra high frequency PD sensors has become an important topic. This article predicts the reliability and lifespan of sensors using performance degradation data by establishing an inverse Gaussian model. Firstly, the working performance and degradation mechanism of Ultra high frequency PD sensor are analyzed, and the output port voltage is determined as the performance degradation reference; Then, by selecting multiple groups of test data, the constraint relationship between drift parameters and diffusion parameters of the Inverse Gaussian Process is calculated, and the failure criteria are finally determined. The reliability function and reliability life of Ultra high frequency partial discharge sensors under normal operating temperature conditions are obtained, which verifies the feasibility of the reliability prediction method based on the inverse Gaussian process.

In the position sensorless control of permanent magnet synchronous motor (PMSM) based on pulsed vibration high-frequency voltage injection method, the position detection accuracy is very important. In this paper, firstly, the second harmonic error brought by the asymmetry of motor three-phase inductance to the sensorless control of PMSM based on carrier signal injection is theoretically analyzed, the specific expression of the second harmonic error is derived, and simulations are carried out to verify it. In addition, a novel position observation structure is proposed to suppress the second harmonic error using a second-order generalized integrator (SOGI), and a new strategy for suppressing the second harmonic error in combination with SOGI is proposed. Finally, simulation experiments using MATLAB/Simulink are conducted to verify that the proposed strategy can not only have better static performance, but also effectively eliminate the second harmonic error of position estimation during sudden changes in PMSM speed and load.

AC filters are important equipment in HVDC projects. In the operation and maintenance process, the frequent throwing of the AC filter will seriously affect the life of the circuit breaker. Its operating condition determines the voltage quality of the transmission system, so it is necessary to carry out a comprehensive life assessment of the circuit breaker for AC filters. In this paper, we have studied and analyzed the returned disassembly reports of circuit breakers, obtained some characteristic quantities during the operation of the circuit breaker and analyzed the relationship between the life of each circuit breaker component-contacts, operating mechanism, lightning arrester and seals and its corresponding characteristic quantities. The ageing estimation of the overall circuit breaker is summarized by combining the ageing mechanism of the various components, and reference maintenance strategies are provided.

Power inspection is a crucial aspect in ensuring the safety and stability of electrical equipment. To address the challenges of high difficulty and low efficiency in substation inspection tasks, a novel approach is presented in this paper – a substation inspection robot path planning method based on a genetic simulated annealing algorithm. This method involves applying simulated annealing to the offspring population generated through selection, crossover, and mutation operations in the genetic algorithm. The result is the derivation of the optimal path for the inspection robot within the substation. Compared to traditional genetic algorithms and simulated annealing algorithms, this approach offers distinct advantages. It demonstrates superior optimization capabilities and convergence properties, effectively resolving the intricate path planning predicaments faced by inspection robots within substations. By synergizing the strengths of genetic algorithms and simulated annealing, this method surpasses the limitations of each technique in isolation.

The ageing studies of silicon rubber applied for the gasket material in wet capacitors were proposed in the present study. Based on the extreme environment of high-altitude area, the silicon rubbers were impregnated in benzyl toluene (M/DBT) with the high-low temperature cycling, and the microstructure and the mechanical properties of silicon rubber were measured at 336 h, 672 h and 1500 h respectively. Results showed that M/DBT molecules could diffuse into the silicon rubber, causing the swelling of silicon rubber. Meanwhile the precipitated additives from the silicon rubber together with the scission of Si-O-Si and Si-CH3 gave rise to the erosion surface morphology. The destruction of physical crosslink and the encouragement of chemical crosslink caused the first rising and then dropping of the total crosslink degree. Consequently, both the hardness and the tensile strength first went down and then went up with the ageing time going by, which reached the minimum value at 672 h. The increased hardness and degraded elasticity finally brought about the failure of the sealing ring.

The cross-linked polyethylene (XLPE) is widely used in the insulation of the seam cable because it has good electrical performance, mechanical performance and heat resistance, and it is the basis for ensuring the insulation and safeness of the waters. However, during operation, high voltage 500 kV submarine cable is susceptible to complex thermal, electrical, mechanical and environmental stresses, resulting in an intrinsic aging process with time-varying characteristics of the cable insulation medium. Therefore, it is of great significance to carry out the analysis of the deterioration characteristics of insulation medium and the non-destructive state evaluation method of high voltage 500 kV submarine cable for the operation and maintenance of submarine cable. In this paper, the high-voltage frequency domain dielectric response test of XLPE submarine cable under different test voltage and different test temperature conditions is carried out, and the results show that the dielectric loss factor of the tested submarine cable gradually increases with the increase of test voltage and test temperature in the frequency range of 10−3–10−1 Hz. The correlation between the relative loss λ and the elongation at break retention rate K at different test temperatures is established, and a method for evaluating the insulation aging state of XLPE submarine cable is proposed to realize the effective evaluation of the insulation aging state of submarine cable.

In order to reduce the cogging torque of a six-phase permanent magnet synchronous motor, this paper proposes a multi-parameter composite optimization method to reduce cogging torque by using a 10-pole 12-slot six-phase permanent magnet synchronous motor as the research object. By analyzing the mechanism of cogging torque generation, the finite element models of polar arc coefficients and eccentric magnetic poles are parametrically analyzed separately to study their effects on cogging torque. The response surface method is used to solve for the combination of pole arc coefficient and eccentric chipping pole to find the optimal pole arc coefficient and the appropriate eccentric distance. The corresponding finite element models are established based on the parameters before and after optimization, and the performance parameters such as cogging torque, no-load back EMF, air gap flux density, and output torque are compared. The results show that the method reduces the cogging torque by 99.7%, which has a significant optimization effect and verifies the effectiveness and feasibility of the method.

With the rapid development of the power grid system, the impact of noise generated by vibration on the lifespan of power equipment and the health of surrounding residents is becoming prominent. One of the main sources of vibration and noise of power equipment is the magnetostrictive effect of electrical steel materials and the electromagnetic interaction among core laminations. This article mainly investigated the core deformation and stress sensitivity caused by magnetostriction in a single-phase double column transformer. Firstly, the magnetic field and structural force field of a single-phase double column transformer core were simulated, and the core deformation caused by magnetostrictive effect of electrical steel sheet was analyzed. Secondly, the single-phase transformer core model was setup experimentally, its local vibration deformation was measured, and the simulated results were verified compared with the measured ones. Finally, the variation law of core vibration acceleration under the influence of mechanical stress was measured and analyzed.

Accurately estimating the State of Charge (SOC), State of Health (SOH), and predicting the Remaining Useful Life (RUL) of lithium-ion batteries is crucial for extending their lifespan and ensuring system safety. Researchers worldwide have extensively studied methods for battery state assessment and life prediction, proposing various approaches.This article begins by introducing existing estimation methods for SOC and SOH, analyzing their strengths and weaknesses. Additionally, it explores leveraging machine learning and deep learning to uncover key parameters in battery management algorithms. Subsequently, it defines RUL and categorizes and compares existing methods for RUL estimation, discussing how to judiciously apply RUL estimation in practical battery management.Finally, the paper delves into potential challenges and future directions for lithium-ion battery management systems.

Currently, the deployment of converter station applications faces some challenges, such as complex resource dependencies and long deployment cycles, which severely hinder the efficient operation of converter stations. In response to these issues, this paper has analyzed the deployment processes of containerized applications and virtual machine-based applications, then proposed an application deployment metamodel framework. By defining deployment package specifications, a metamodel-based systematic application deployment model has been constructed, and intelligent analysis for converter station applications deployment has been carried out. This model focuses on defining and describing the overall architecture and configuration of applications, achieving decoupling between application deployment and application development, as well as with the runtime platform. This enables application publishers to concentrate more on core functionalities’ implementation while making application subscribers’ deployment process more efficient and convenient. As a result, the digital cloud-edge collaborative pathway of converter stations becomes smoother.

In order to enhance the electromagnetic characteristics for new energy vehicle (NEV) drive motors, an optimization design combining of the taguchi method and genetic algorithm is developed in this paper. The optimization concentrates on the rotor structure, and the variables are thickness of large and small magnets, angle of large and small magnets, and polar arc coefficients of large and small magnets. Employing a genetic algorithm with elite strategy, the quantities of torque ripple, line back EMF harmonic distortion, peak torque ripple, unit cost output torque, and electromagnetic force are solved. The taguchi method is used to uncover the sensitivity between variables and objectives, and the unique mutation operator for each variable is established. The best results are obtained through the selection of these mutation operators and selection operators. The research results demonstrate that, compared to the initial proposal, the optimized objective meets all technical specifications and effectively reduces noise. It confirms the feasibility and superiority of the current genetic algorithm, as well as its practical value in engineering.

Loose contact, insulation aging, damage and other reasons of electrical circuitry in power supply and distribution system or equipment will lead to the occurrence of arc fault, and arc fault is one of the main causes of electrical fire accidents. Arc fault detection device (AFDD) is a new type of protection device, which can detect the series arc fault in the line. When the series arc fault occurs, the fault current is usually lower than the threshold of the traditional protection device, and it is difficult to achieve timely protection. The research and development of AFDD has reduced the occurrence of fire accidents to a certain extent. The performance of AFDD on the market is uneven, and the detection accuracy of AFDD produced by different companies for different types of loads is different. In this paper, the performances of four AFDDs produced by different companies at home and abroad are compared, and four typical household load combinations are selected to carry out experiments. The experimental results show that AFDD4 without control function has the highest detection accuracy under all load conditions, with an average accuracy of 99.4% and the shortest response time. Among the three AFDDs with control functions, AFDD1 has the best overall performance and the highest average accuracy, reaching 87.2%.