Transactions of China Electrotechnical Society 2024 No. 17 Item and Abstract

Transactions of China Electrotechnical Society is a comprehensive academic journal in the field of electrical engineering sponsored by the China Electrotechnical Society, reporting international and domestic leading academic and scientific research achievements in basic theoretical research and engineering application. Ma Weiming, academician of the Chinese Academy of Engineering, is the director of the editorial board of the Journal and the editor-in-chief of the journal.

Electrical Theory and New Technologies

Electromagnetic field calculation method based on physical information neural network

Author: Zhang Yujiao; SUN Hongda; ZHAO Zhitao; XU Bin; Huang Xiongfeng

Abstract:Physical Information Neural Networks (PINNs) encode partial differential equations (PDEs) and their solution conditions into the network, so that the residuals of PDEs are minimized and the solution conditions are approximated, so that the PDEs can be solved. Due to the problems of local high gradients, difficult training problems caused by source equations, and interface identification problems with high contrast coefficients, PINNs are rarely used in solving electromagnetic field equations due to their low training efficiency and low calculation accuracy.

In this paper, the training difficulty of PINNs in the electromagnetic field is analyzed theoretically, and a modification method is proposed for the form of electromagnetic field PDEs and the neural network architecture, and the electrostatic field and the stable magnetic field based on PINNs are solved, and the calculation results are accurate. The method is extended to the solution of eddy current field in the frequency domain with more complex equations, and the results show that PINNs can ensure good accuracy in the complex frequency domain equations. This research work provides a new idea for the rapid calculation of electromagnetic fields.

Study on electromagnetic force characteristics of permanent magnet electric levitation under multiple working conditions

Author: Cao Ting; SHI Hongfu; LIU Junzhi; Wu Xuejie; Deng Zigang

Abstract:Due to the characteristics of weak damping, the attitude of the magnet is easily changed by external disturbances during operation, which affects the electromagnetic force characteristics of the system. In this paper, the electromagnetic force characteristics of the system are studied by combining analytical calculation, simulation analysis and experimental verification for the tilt, traverse and deflection of the magnet.

Firstly, the structure and principle of the system are described, the magnetic field distribution function of the Halbach permanent magnet array in the horizontal, inclined and deflected states is derived, and a three-dimensional analytical model suitable for multiple working conditions of the system is established. Secondly, a three-dimensional simulation model was built, and the simulation results verified the correctness of the analytical model, and the floating resistance characteristics and levitation capacity of the system under typical working conditions were compared and analyzed in combination with the analytical model. Finally, based on the self-developed dynamic orbit test bench with a maximum design speed of 600 km/h, the electromagnetic force characteristics and vertical self-stability ability of the system under fixed parameters were analyzed, and the accuracy of the analytical model and the electromagnetic force characteristics of the magnet at different traversing positions were verified.

Research on the power transmission characteristics of a new wireless power suspension system based on YBCO high-temperature superconducting coil

Author: Zheng Zhiqiang; Weng Tingkun; LI Zhuo; Shen Liufei; HUANG Shoudao; Zhai Yujia

Abstract:In recent years, the second-generation high-temperature supercoated conductors represented by yttrium-barium copper oxide (YBCO) have been widely used in electric power, medical, transportation, military, energy and other fields due to their extremely high current-carrying capacity and superior mechanical and electromagnetic properties in the temperature range of 20~77 K. In this paper, a small charging suspension system based on YBCO high-temperature superconducting coil is designed and constructed, which can realize both wireless charging and self-stabilizing levitation functions, and can be applied to the wireless charging suspension display for small objects.

Through theoretical derivation and finite element simulation analysis, it is found that the introduction of high-temperature superconducting coils with low resistance and high current-carrying density into the wireless charging system can significantly improve the output power and output efficiency of the system, with a maximum increase of 3 times and 2.6 times, respectively, especially in low frequency bands.

In addition, the experimental results show that the system can maintain a stable suspension and efficient output of load voltage in the range of 10 mm levitation height, which solves the problems of complex device and short continuous power supply time due to the need to design a specific magnetic circuit structure and install a built-in battery or power supply in the existing electromagnetic levitation and electric levitation technologies, and opens up a new direction for the application of superconducting wireless power transfer technology.

Cardiac pacemaker wireless power transmission LCC-LCC magnetically integrated printed helical coil research

Author: Chen Weihua; SONG Yuhang; YAN Xiaoxiao; Yao Jinshu; Ge Shuaishuai

Abstract:In order to reduce the size of the implantable pacemaker wireless power transfer system and improve the transmission performance of the system, a pacemaker wireless power transfer system based on LCC-LCC magnetically integrated printed spiral coil (PSC) is proposed. Firstly, the coil model was established to study the influence of turn width and turn spacing of PSC on the transmission efficiency under the condition of fixed filling ratio, and the optimal coil parameters were determined. Secondly, the simulation models of the non-integrated and integrated coupling mechanisms were established to calculate the magnetic field distribution of the two coupling mechanisms under different offsets. Finally, the non-integrated and integrated wireless power transmission systems are built to verify the advantages of the integrated structure in terms of transmission performance.

The results show that at a transmission distance of 12 mm, the transmission efficiency is increased from 62.3% to 68.1%, and the output power is increased by 0.39 W. In addition, the safety of the system is evaluated by simulating the distribution of electric field strength and specific absorption rate (SAR) values in the human body during wireless charging. The proposal of integrated PCS will help to promote the commercialization of wireless power transfer systems for pacemakers.

Magnetostrictive displacement sensor measures the failure mechanism of the blind zone and the optimization of magnetic shielding

Author: Bian Tiechi; LI Mingming; WANG Xinyu; HUANG Wenmei; Weng Ling

Abstract:There is a measurement blind area near the detection coil of magnetostrictive displacement sensor, and the effective measurement range is difficult to meet the application requirements in the limited installation space. In order to solve this problem, based on the Weidemann effect, the magnetoelastic coupling effect and the Villari effect, the measurement blind zone model of the magnetostrictive displacement sensor under the action of the synthetic magnetic field was established, and the failure mechanism of the sensor in the measurement blind zone was analyzed. The experimental platform was built to provide adjustable pulse current and axial magnetic field, and (Fe83Ga17)99.4B0.6, Fe46.5Ni48.5Cr2Ti2.5Al0.5 and Fe30Co70 waveguide wires with a diameter of 0.6 mm were selected to verify the accuracy of the model.

The magnetostatic shielding device was added and the best parameters were determined, the prototype was made and the test showed that the measurement blind area of the optimized (Fe83Ga17)99.4B0.6 waveguide wire sensor was shortened from 30.05 μs to 18.45 μs, and the width was shortened by 38.6%. The measurement blind area of the Fe46.5Ni48.5Cr2Ti2.5Al0.5 waveguide wire sensor was shortened from 31.15 μs to 19.15 μs, and the width was shortened by 38.5%. The measurement blind zone of the Fe30Co70 waveguide wire sensor is shortened from 29.55 μs to 18.85 μs, and the width is shortened by 36.2%.

A method for characterizing and measuring the metaphysical properties of thermoelectric materials based on quasi-steady state method

Author: Ren Hongrui; HE Hailong; NEW Chunping; Rong Mingzhe; Tian Haoyang

Abstract:Thermoelectric power generation technology can realize the direct conversion of heat energy to electrical energy, and has a wide range of applications in the fields of waste heat utilization, spacecraft power supply and self-powered sensors, and one of its cores is the thermoelectric materials used to realize heat-electricity conversion. The characterization of the physical parameters of thermoelectric materials is of great significance in the application of thermoelectric devices, optimization design, fault diagnosis and other researches. At present, most of the physical property parameter characterization methods of thermoelectric materials consider the thermoelectric parameters of the material to be constant, ignoring the nonlinear correlation between the thermoelectric parameters and temperature, and not fully considering the contact resistance and thermal resistance in the device.

In this paper, a method for the characterization and measurement of metaphysical parameters of thermoelectric materials based on the quasi-steady-state method and the thermoelectric device test device is proposed: firstly, the quasi-steady-state method is proposed to characterize and calculate the physical property parameters of materials, and the correctness of the method is verified by simulation. On this basis, combined with the thermoelectric device test device, the thermoelectric materials are characterized by experiments, and the results show that the maximum error between the test results and the manufacturer's parameters is only 4.3%, which can achieve accurate characterization of the thermoelectric parameters. This method can accurately characterize the physical parameters of thermoelectric materials in a wider temperature range, enrich the functions of thermoelectric device test equipment, and reduce the equipment investment and testing cost of material testing equipment.

Self-calibration analysis and measurement uncertainty assessment of Rydberg atomic electric field sensors

Author: Xiao Dongping; Shi Zhuxin; YAN Sheng; ZHANG Huaiqing; Yu Chuanxiang

Abstract:Traditional electric field sensors require standard field or higher accuracy level sensors for calibration, while Rydberg atomic electric field measurements based on atomic intrinsic energy level structure and spectral characteristics can be traced back to fundamental physical constants, and quantum sensing has its own calibration function.

In this paper, the quantum coherence effect of the interaction between the Rydberg atom and the external field is described, the electric field measurement principle of the Rydberg atom sensor is explained, and its self-calibration is analyzed. Based on the Rydberg atomic sensing measurement system for low-frequency electric field, the error sources are analyzed, various uncertainty components are defined and calculated, and the synthetic relative standard uncertainty is 3.885%. Conservatively, the extended uncertainty is 7.77% under the inclusion probability greater than or equal to 95.45%. In this process, the main influencing factors of uncertainty are identified and suggestions are put forward to reduce their impact. Finally, the fitting function between the measured electromagnetic induced transparency (EIT) spectral frequency shift and the electric field strength of the sensing system is given, and the fitting certainty coefficient reaches 0.996 9, which verifies the accuracy of the constructed low-frequency electric field quantum measurement system.

Optimization of winding baffle structure of oil-immersed transformer based on the radial basis function response surface model of whale optimization algorithm hyperparameter optimization

Author: Liu Gang; GAO Chenglong; HU Wanjun; LIU Yunpeng; Li Lin

Abstract:In order to improve the stability of transformer operation, the radial basis function (RBF) response surface model is used to optimize the size of the transformer winding baffle and improve the oil flow distribution to achieve better heat dissipation. In order to improve the fitting accuracy of the RBF response surface model, the whale optimization algorithm (WOA) is used to optimize the hyperparameter values of the radial basis function, and compared with the traditional grid search (GS) optimization method and the definite parameter RBF model. The comparison results show that for the hyperparameter optimization problem, the WOA optimization efficiency is 3.13 times that of the GS optimization method under the premise that the fitting accuracy is superior.

On this basis, the structure size of the winding baffle is optimized based on the WOA-RBF response surface model, and the optimized hot spot temperature is reduced by 3.81°C compared with the hot spot temperature of the initial structure, and the maximum temperature rise is reduced by 13.42% relative to the whole field, and the overall temperature rise of the winding is effectively reduced. At the same time, the proposed algorithm is compared with the optimization results of Genetic Algorithm (GA), and the optimization efficiency of the WOA-RBF response surface model is 13.41 times that of GA while ensuring the accuracy. According to the analysis of the above results, it can be seen that the proposed algorithm has good optimization performance, and compared with the genetic algorithm, it can significantly improve the optimization efficiency while ensuring the optimization accuracy.

Research on automatic segmentation switching technology without communication in dynamic wireless power supply system of automatic guided vehicle

Author: Jing Rui; ZHANG Yao; LIU Shunpan; ZHOU Lingyun; Wang Zhoulong et al

Abstract:In order to reduce the complexity of position detection and segment handover in dynamic wireless power supply system of automated guided vehicle (AGV), an automatic segment handover technology integrating non-communication position detection function is proposed. The position detection coil is wound around the transmitting coil, and the transmitting coil and the detection coil are decoupled by decoupling capacitors, and when the receiving coil moves above the transmitter coil, the detection coil will only induce a voltage in the magnetic field of the receiving coil, which is the position signal of the receiving coil. Combined with the proposed transmission coil segmentation switching strategy, the induced voltage is used to drive the segmentation switching switch, and the corresponding transmitter coil is automatically turned on. There is no need for communication, segment switching controller, auxiliary power supply, etc., and position detection and segment switching can be completed at the same time.

The experimental results of the 500 W power level prototype show that when the receiver coil moves, the position of the receiver coil can be accurately detected by the detector coil, and the detector coil can drive the transmitter coil to switch in the correct sequence, which is consistent with the theoretical analysis.

An online capacity estimation method based on the half-peak area of the capacity increment curve of lithium-ion batteries

Author: Li Leqing; WANG Peng; SUN Wanzhou; Peng Peng; Duan Yanzhou et al

Abstract:The continuous breakthrough and large-scale application of key materials for lithium-ion batteries is an important technical path for the realization of the dual carbon goal in mainland China. However, due to the complexity of the battery's ready-to-use decay and aging characteristics, accurate aging analysis and capacity estimation are extremely difficult. Therefore, the mapping relationship between the half-peak area and life attenuation of the battery capacity increment curve is discovered, and the maximum usable capacity estimation method based on the characteristic peak half-peak area of the charging capacity increment curve is proposed, and the available lithium loss is clarified as the main capacity decline mode of the battery. Considering the influence of ambient temperature and charging rate on the capacity estimation algorithm, a capacity optimization estimation algorithm based on ambient temperature and charging rate is further established, and the verification results of different aging states and batteries show that the maximum usable capacity estimation error is less than 3%.

Power Systems & Integrated Energy

Research on transient real-time simulation of new energy low-voltage DC distribution system based on FPGA

Author: Wang Shouxiang; ZHANG Chunyu; Zhao Qianyu

Abstract:The transient real-time simulation of the new energy low-voltage DC distribution system plays an important role in optimizing its operation control. Due to the integration of a large number of circuits with different functions inside field-programmable gate arrays (FPGAs), FPGAs are becoming one of the main computing carriers in the field of transient real-time simulation of power systems. In order to meet the transient real-time simulation requirements of new energy low-voltage DC distribution system, a transient real-time simulator for new energy low-voltage DC distribution system based on FPGA including small distributed wind power generation, photovoltaic power generation and battery energy storage unit is developed.

Firstly, the computing modules of distributed generation units and typical control loops were constructed, and the parallel computing characteristics of FPGA were used to establish the series-parallel hybrid solution structure of the underlying modules by combining the concept of "algorithm-structure-effective matching (AAA)". Then, under the framework of the node analysis method, a parallel solution method for the conductivity matrix of electrical system nodes combining matrix LDU decomposition and Directed Acyclic Graph (DAG) is established. Finally, on the basis of establishing the parallel solution architecture of electrical system and control system, a transient real-time simulator for new energy low-voltage DC distribution system based on FPGA was developed, and the effectiveness and accuracy of the developed transient real-time simulator were verified by comparing the simulation results with the calculation results of the PSCAD/EMTDC offline simulation platform.

Mechanism and suppression method of active step-down arc extinguishing based on the change characteristics of generator stator grounding arc resistance

Author: Li Li; YU Kun; ZENG Xiangjun; WANG Zhan; He Shigeng

Abstract:The arc fault of stator grounding is a technical bottleneck that restricts the safe and reliable operation of large generators. In order to solve the problem of insulation breakdown and core damage caused by the grounding arc of the stator winding, a flexible grounding active step-down arc extinguishing method based on the change characteristics of the arc resistance of the generator stator grounding is proposed.

In this paper, the analytical relationship between the arc resistance of the stator grounding and the arc voltage is established, and the variation law of the increase of the grounding arc resistance is revealed during the decrease of the voltage at the stator grounding fault point. When the voltage of the ground fault point is suppressed below the arc re-ignition voltage, the suppression method of returning the breakdown gap of the stator winding to the normal insulation state is clarified. According to the step-down arc extinguishing strategy of the flexible grounding mode of the stator of large generators, in the arcing stage of the grounding fault, the neutral point voltage source outputs the power frequency of the fault point and the reverse potential of the 3rd harmonic, actively reduces the voltage at the fault point, reduces the voltage at the fault point below the arc voltage, and extinguishes the grounding arc of the stator. The injection signal is used to perceive the state of the stator grounding arc, and the change trend of the vector angle of the stator damping rate is monitored in real time, so as to determine whether the grounding arc fault is eliminated in the process of step-down arc reduction.

The proposed method does not need to reduce the voltage at the fault point to zero, which can effectively reduce the voltage rise of the non-fault phase and reduce the breakdown risk in the winding groove of the stator non-fault phase. The arcing condition of stator grounding fault was simulated in the PSCAD/EMTDC simulation environment, and the proposed method was tested and verified.

The test results show that the flexible grounding arc suppression method based on the variation characteristics of stator grounding arc resistance can actively reduce the voltage of stator grounding fault points, help increase the return of insulation resistance at fault point gaps, inhibit grounding arc reignition, reduce the risk of stator non-fault phase insulation breakdown, and realize reliable arc suppression of stator grounding arc faults.

The influence of action delay and measure quantity on the control effectiveness of low inertia system in frequency emergency control

Author: Li Zhaowei; FANG Yongjie; Wu Xuelian; LI Jianhua; Lai Yening

Abstract:Frequency emergency control is the second line of defense to ensure the frequency safety after the power grid failure, which is usually realized by the event-triggered stability control system, and has become the standard configuration to support the safe power transmission of UHVDC. With the rapid development of a high proportion of new energy, the frequency modulation ability and inertia level of the system are decreasing, and the frequency response characteristics of the power grid after the fault have the new characteristics of large drop depth and fast speed, and whether the emergency control can be effective is the key factor related to the frequency safety of the system.

In this paper, a frequency response model and transfer function of a high-proportion renewable energy power system considering frequency emergency control are established. Secondly, from the aspects of permanent disturbance and short-term disturbance, the frequency response characteristics of the system, the effectiveness of the action delay and the amount of measures for the emergency control of the frequency are analyzed in detail, and the limit of the proportion of new energy access when the emergency control is effective is given. Finally, the time-domain simulation verification is carried out based on the actual power grid simulation model, and it is pointed out that the interlocking short-term power disturbance caused by the short-circuit fault of the low-inertia power system will become the key and difficult point of frequency security defense.

Regional equivalent inertia evaluation method of new energy power system based on measurement data

Author: Ma Yanfeng; LI Jinyuan; Wang Zijian; ZHAO Shuqiang; Guo Runsheng

Abstract:The different types, permeability and control methods of new energy power generation will affect the real-time inertia of the power system, and the evaluation of the inertia level is helpful to improve the anti-disturbance ability of the power system. Based on the analysis of the virtual inertial response characteristics of wind power and photovoltaic power and its influence on the frequency stability of the power system, and considering the characteristics of the load static voltage, a real-time evaluation method of regional equivalent inertia of the new energy power system based on the measured data is proposed. The evaluation results take into account the generator inertia, the new energy virtual inertia and the load equivalent inertia.

In order to reduce the error caused by the frequency distribution characteristics after disturbance, the selection of frequency sampling points and the calculation method of regional frequency are proposed from the perspective of weighted average, which solves the problem of large number of measurement data and difficult acquisition. A numerical example is given to verify the feasibility and effectiveness of the proposed method for the evaluation of regional equivalent inertia of both traditional power system and new energy power system.

Communication queue scheduling strategy for intelligent substation based on asynchronous shaping mechanism

Author: Jia Huibin; Wu Wenrui; WU Kun; LIU Yu; Chang Naichao

Abstract:Time-sensitive networks (TSNs) have attracted extensive attention because they can provide deterministic low-latency transmission services for key communication services in smart substations. In order to solve the problem that the existing communication queue scheduling strategy of industrial Ethernet switches in substation is difficult to ensure the real-time and reliability of key communication services theoretically, a communication queue scheduling strategy for intelligent substation based on TSN Asynchronous Shaping Mechanism (ATS) is proposed.

Firstly, based on the service quality requirements and transmission characteristics of intelligent substation service flow, the priority division and shaping queue allocation scheme of intelligent substation service flow were proposed. Secondly, a shaper parameter optimization model with the goal of minimizing the end-to-end delay of service flow is established, and the solution is solved by the interior point optimization algorithm. Finally, the shaper uses the token-bucket-based traffic shaping method to shape the divided service flows, and the shaped traffic is scheduled for transmission based on the strict priority algorithm. Simulation experiments are carried out based on OMNet++, and the experimental results show that the proposed method can ensure the deterministic low-latency transmission of key communication services.

Federated learning incentive mechanism for image object detection of power inspection

Author: Zhong Linlin; Liu Keyu

Abstract:The object detection algorithm based on deep learning can efficiently process power inspection images and find hidden faults in time. However, due to data integration difficulties and data privacy protection, a single power company or third-party organization may not be able to train a high-performance model. In order to solve this problem and motivate more participants to join the federated learning for power inspection image object detection, a federated incentive mechanism for power inspection image object detection based on model fairness and benefit fairness is constructed. The incentive mechanism based on model fairness is applicable to the situation where all participants are data owners, and the model with different performance is allocated through contribution evaluation; The incentive mechanism based on revenue fairness aims at the model where there is both a data owner and a data demander, and the data owner gets the corresponding benefits, while the data demander gets a high-performance model.

The experimental results show that the fairness correlation coefficients can reach 0.96 and 1 respectively in the two incentive mechanisms. This indicates that the proposed incentive mechanism can effectively improve the fairness and motivate more participants to join the federated learning for image object detection of power inspection.

Research on the uniqueness recognition of pins in aerial power tower images

Author: Yan Guangwei; Ma Yilin; JIAO Runhai; He Hui

Abstract:In recent years, defect pin detection technology based on deep learning has been widely used in the inspection of power towers. However, this technology can only locate the defective pin in the image space, and cannot accurately give the unique number of the corresponding pin of the defective pin in the actual power tower. In order to solve this problem, a unique identification method of defect pins based on deep learning and 3D reprojection is proposed.

Firstly, by constructing the three-dimensional model of the inspection power tower system, the number of the component model in the power tower system was obtained, and the coordinates of the vertex and center points of the three-dimensional space bounding box of the component model were calculated. Secondly, the YOLOv5 model was used to detect pins and context-dependent objects in the image space. Thirdly, the camera pose estimation algorithm based on structural constraints is used to estimate the camera pose of aerial images. Finally, the pin bracket box in the 3D power tower system is reprojected according to the camera pose to calculate the matching degree with the pin detection frame, and the pin detection frame with a specific number is output in the image space. Based on the pin detection frame output by the YOLOv5 model, the uniqueness recognition accuracy of the pin is 100%, and the accuracy of the uniqueness recognition obtained by the experiment using the simulation data is 100%, and the accuracy of the uniqueness recognition obtained by the experiment using the real data is 93.3%, which verifies the effectiveness of the pin uniqueness recognition method proposed in this paper.

Through the unique identification of defective pins, the workload of manual secondary review of fault images can be reduced, and the number and specific location information of defective pins can be accurately counted, so as to provide support for refined management such as follow-up fault maintenance and fault correlation analysis.

High voltage and discharge

Research progress on plasma catalysis and its application in power multivariate conversion

Author: Li Tianyu; SUN Jing; GAO Yuting; Qu Zhongping; Zhou Renwu

Abstract:With the continuous development of new energy technology, Power-to-X has gradually become an important research direction in the field of low-carbon transition. Atmospheric pressure cryogenic plasma technology has become a well-anticipated solution due to its ability to adapt to the intermittency and fluctuation of renewable energy power supply systems such as wind and solar. By using renewable electricity to generate plasma under mild conditions, it directly drives the production and emission reduction of high-value products, which provides a strong guarantee for the realization of the "dual carbon" goal.

In this paper, the common types of plasma discharge are introduced, and the complex synergistic effects between plasma and catalyst are illustrated with examples. Secondly, the progress of three typical research cases at home and abroad in plasma-catalyzed CO2 conversion, plasma-catalyzed nitrogen fixation and plasma-catalyzed CH4 reforming is summarized. Finally, based on the current research status, the problems and challenges faced by plasma catalysis in Power-to-X technology are analyzed, and the prospect of laboratory research and commercialization of plasma catalysis is proposed.

In conclusion, further research on plasma catalysis technology and its important application in sustainable development and low-carbon economy is of positive significance for promoting the use of clean energy and reducing carbon emissions.

A review of anti-icing/de-icing methods for wind turbine blades under icing conditions

Author: Hu Qin; WANG Huan; Shu Lichun; JIANG Xingliang; Xia Hanlin

Abstract:The icing of wind turbine blades in iced areas will lead to power loss, and timely prevention and treatment of blade icing disasters will help to ensure the safe, stable and reliable operation of wind turbines. In this paper, the research status of anti-icing methods for wind turbine blades under icing conditions is reviewed. Firstly, the mechanism and icing characteristics of blade icing were introduced, the effects of blade icing on its lift coefficient, drag coefficient and power loss were summarized, and the current challenges were analyzed. Secondly, the principles and advantages and disadvantages of the existing blade active anti-icing, passive anti-icing and collaborative anti-icing methods were reviewed, and a comprehensive comparative analysis was carried out. Finally, the key scientific problems and economic feasibility of blade icing are analyzed from a holistic perspective, and the future research trends are given, and it is believed that the electrothermal method, the electric pulse method, the aerodynamic pulse method, the ice-trapping coating and the collaborative anti-icing and de-icing method with electrothermal function are very promising in wind turbine blades.

High-current, high-speed sliding electrical contact interface heat distribution process

Author: Yao Jinming; Fu Qiang

Abstract:In the environment of high-current and high-speed sliding electrical contact, aluminum deposition occurs on the orbit surface after multiple launches. The melting and abrasion of the armature and the aluminum deposition layer under the action of the interfacial heat source will change the contact state, which will seriously affect the sliding electrical contact performance. The heat distribution characteristics of the interfacial heat source between the armature and the sedimentary layer track are the basis for studying the melting and wear of interfacial materials, so it is necessary to study the heat distribution process of the sliding electrical contact interface.

In this paper, the heat transfer model of the armature and sedimentary orbits is established, and the temperature distribution equations of the armature and sedimentary orbits are obtained. According to the continuity of the interfacial temperature, the governing equation of heat distribution is derived, and the error function is optimized by using the least squares estimation method, and a numerical calculation model of interfacial heat distribution based on the least squares estimation method is proposed. Based on the numerical calculation model of heat distribution, the influence of thermal parameters and velocity on the thermal distribution characteristics of materials is studied and analyzed, and the results show that the thermal parameters of materials affect the initial value of the heat distribution curve, and the velocity affects the decay rate of the heat distribution curve, and the higher the velocity, the faster the heat distribution decays with time.

Finally, the physical mechanism of the thermal partition process at the pivotal orbit interface is discussed through theoretical analysis, and the results of theoretical analysis are consistent with the results of numerical calculations. The research results can provide a deeper understanding of the interfacial thermal process and provide technical support for the study of the melting and wear characteristics of interfacial materials.

It can be used for the simulation study of the tensile fracture process of liquid metal bridges in the research and development of microswitches

Author: Zhu Xiaonan; YANG Fei; ZHANG Yunxuan; SUN Jinru; Rong Mingzhe

Abstract:The construction of a fluid simulation model can effectively analyze the fluid dynamics during the tensile fracture process of liquid bridges, and provide guidance for the control of arc breaking performance based on the tensile fracture process of liquid metal bridges. The existing simulation models of liquid bridges are based on dynamic mesh or other mesh deformation methods, and cannot simulate the large-scale tensile deformation and geometric fracture of liquid bridges. To solve this problem, a finite element simulation method for tensile fracture of liquid bridges without relying on mesh deformation is proposed.

In this method, the maximum viscosity value is set for the liquid, and the solid is approximated in the immovable liquid area, and the tensile fracture process of the liquid bridge is simulated by calculating the stretch of the equivalent liquid bridge flowing out of the domain through the movement of the maximum viscosity value boundary. Based on the simulation model, the influence of the volume and tensile velocity of the liquid bridge on the tensile fracture process of the liquid bridge was explored, and the transformation law of the tensile fracture characteristics of the liquid bridge in the whole tensile speed range was obtained. Finally, combined with the experimental results, the influence of the transition of tensile fracture characteristics of the liquid bridge on the arc combustion mode is analyzed, and the phase diagram of the arc combustion mode transition in the full tensile speed range is given, which provides a basis for the control of the arc breaking performance of the liquid bridge switch.

The research content of this paper is of guiding significance for the research and development of micro switches based on the principle of liquid bridge fracture, such as miniature relays and contactors.

Identification and data reconstruction of dissolved gas outliers in power transformer oil

Author: Jiang Jun; ZHANG Wenqian; Appl; LI Xiaohan; Fan Lidong

Abstract:High-quality sensing data is the basis for driving the digital and intelligent development of new power systems, but due to sensor performance degradation, transmission interruption or other interference factors, errors and outliers often occur in the data, resulting in low data utilization. In view of the online monitoring data of dissolved gas in in-service power transformer oil, a joint method based on COPOD, isolated forest (IForest) and Grub bs is proposed to improve the value of dissolved gas data in oil.

Firstly, the dataset containing outliers was screened out by COPOD and IForest, and then Grub bs was used to test the outliers to effectively identify the outliers. Furthermore, the mask method is used to optimize the training of the Transformer neural network model, and the data sequence of dissolved gas in oil is reconstructed by filling in the vacant value. Compared with the traditional K-nearest neighbor algorithm, the proposed algorithm improves the number of correct identification points, the correct identification of outlier points and the average area of the receiver operating characteristic curve by 3.5%, 29.4% and 5.0%, respectively, compared with the traditional K-nearest neighbor algorithm. For data filling, compared with the two-way scaling algorithm, the mean root mean error between the filled data and the actual data is 7.29 μL/L, and the mean absolute error is 2.7 μL/L, which improves the performance by 9.7% and 9.2%, respectively, effectively improving the quality and utilization of data. Finally, the analysis of dissolved gases in oil of 11 500 kV transformers was carried out, which strongly supported the status evaluation of transformers and the digital management of equipment.

Charge calculation and influencing factors of metal particle groups in flow-electric coupling field

Author: Zhang Ning; WANG Peng; LIU Zhijie; LIU Gongzhi; He Bo

Abstract:The charge distribution of metal particles in insulating oil is the key to study the motion characteristics of particles and the partial discharge and breakdown behavior in insulating oil. In this paper, an oil tunnel simulation observation system is built, and the motion model of metal particles in the liquid-solid interaction system is constructed by using the method of dynamic analysis, and on this basis, the particle image velocity measurement (PIV) is proposed to calculate the particle charge. The effects of different oil flow velocities, voltage levels and voltage types on the distribution of particle charge and their mechanism were analyzed.

The results show that the charge of particles in oil calculated based on PIV is similar to that of the traditional model, and the distribution curve of the proportion of charge of metal particles in insulating oil is close to Gaussian distribution, which is due to the charge transfer or neutralization of the collision between particles. The increase of the flow velocity under the DC voltage will hinder the charge transfer between the particles, increase the probability of collision between the particles and the plates, and lead to the decrease of the particle charge. The increase of voltage level will change the streamline of the particle group from flat to oscillating, and the particle charge will generally increase. Compared with DC voltage, at AC voltage, particles with large charge account for more.

Aging phenomenon of composite insulators based on the change of silicone rubber molecular chain traps

Author: Shen Yao; LIU Xingjie; LIANG Ying; Bo Tianli; Zhao Tao

Abstract:After the aging of silicone rubber composite insulators, it is easy to introduce strong polar groups such as vinyl, carbonyl and hydroxyl groups, which form chemical traps, which will aggravate the aging of insulators and even cause insulation accidents. In order to explore the trap characteristics of different chemical groups after aging of silicone rubber, the defect models of PDMS containing carbonyl, hydroxyl and vinyl groups were constructed by molecular simulation software using polydimethylsiloxane (PDMS) as the matrix, and the bond length, bond angle, atomic layout and dipole moment changes of PDMS with different structures under the action of electric field were calculated by first principles for the defect models after stable configuration, and the corresponding trap energy levels and density of states distribution changes were obtained. By analyzing the internal relationship between the micromolecular structure and trap characteristics of different defect models, the variation law of different chemical traps under the action of electric field was explored.

The results showed that the hydroxyl PDMS introduced a shallow trap, while the vinyl and carbonyl PDMS introduced a deep trap. The trap depths of the three defects all increased with the increase of the electric field, and the change rates were carbonyl, vinyl and hydroxyl in descending order. With the increase of the electric field, hole traps appeared in the structure of vinyl-containing PDMS, and electron traps in carbonyl-containing PDMS dissipated, while the trap distribution of hydroxyl PDMS did not change much. It can be seen that the role of the carbonyl group formed after the aging of silicone rubber cannot be ignored in its aging process. The trap state and group content of silicone rubber after aging are expected to be used as a new reference standard for the evaluation of silicone rubber aging, which can provide a theoretical basis for silicone rubber aging experiments.

Electric field design of integrated high-voltage vacuum interrupter based on two-gap asynchronous linkage

Author: Ge Guowei; WANG Wenbo; CHENG Xian; CHEN Hui; Duan Xiaohui

Abstract:In order to overcome the problems of single-break vacuum interrupter insulation bottleneck and complex multi-fracture series structure, an integrated high-voltage vacuum interrupter structure based on two-gap asynchronous linkage is proposed, which adopts the auxiliary gap and the main gap series asynchronous linkage, and the auxiliary gap assists the main gap insulation and arc extinguishing, which is expected to realize the engineering application of vacuum interrupter with voltage level of 252 kV and above. The electric field simulation model of the integrated high-voltage vacuum interrupter with asynchronous linkage between two gaps was established, and the influence of the direction of the incoming and outgoing lines, the main and auxiliary clearances, and the shielding cover on the relationship between the electric field strength and the voltage distribution was analyzed, and the effects of the shielding cover structure and the annular ceramic voltage-dividing capacitor on the electric field improvement were studied.

The results show that when the static end cover is the outlet end and the moving end cover is the inlet end, the main gap opening distance is 60 mm and the auxiliary gap opening distance is 30 mm, which can meet the distribution of the partial voltage relationship according to the opening distance, and the maximum electric field strength is reduced by 27.3% compared with the long gap opening distance of 60 mm. The maximum electric field strength of the arc extinguisher of the external parallel annular ceramic divider capacitor is reduced by about 30% compared with that of the interrupter without parallel capacitor when the incoming end is covered at the static end, which preliminarily illustrates the feasibility and effectiveness of the integrated high-voltage vacuum interrupter structure based on two-gap asynchronous linkage, and the research can provide new ideas and new methods for the development of high-voltage vacuum interrupter.