Table of Content

28 February 2024, Volume 0 Issue 2

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Arc Detection & Research

Research and Analysis on Laser-Induced Discharge Arc Characteristics of Spacecraft Solar Array

WEI Dejie, ZHU Liying, WU Jianwen, TONG Ziang

2024, 0(2):  1-5.  doi:10.16628/j.cnki.2095-8188.2024.02.001

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The discharge arc of solar array seriously threatens the reliable operation and safe life of spacecraft. Based on the discharge arc theory of solar array in space plasma environment, the discharge arc mechanism of high-energy pulse laser-induced solar array was analyzed. The discharge arc characteristics of solar array under three different working conditions were studied by using space discharge ground simulation experiment system. The energy density thresholds of laser-induced discharge arc under three working conditions were obtained, which were about 1.8×10⁸ W/cm², 1.45×10⁸ W/cm² and1.08×10⁸ W/cm², respectively. In the Low-Earth-Orbit plasma environment, the probability of each pulse laser-induced discharge arc is about 60%, and the peak value of the laser-induced discharge arc current is 5.4 A, and the average duration is 16.68 μs, which is very easy to cause great harm to the solar array.

Arc Simulation and Performance Optimization of Non-Polar Low Voltage DC Circuit Breaker Based on Magnetohydrodynamics

WEN Hui, GUO Xiaoxue, ZENG Xinyi

2024, 0(2):  6-12.  doi:10.16628/j.cnki.2095-8188.2024.02.002

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In response to the problem that traditional low voltage DC circuit breakers weaken their arc extinguishing ability when the current is reversed due to the unidirectional magnetic field, the arc simulation model of non-polar low-voltage Dc circuit breaker based on COMSOL is established to analyze the arc motion of non-polar low-voltage Dc circuit breaker under the reverse current. The influence of magnetic field and current on the arc-extinguishing ability of non-polar low-voltage Dc circuit breaker is analyzed. The simulation results show that the non-polar low-voltage Dc circuit breaker can eliminate the blocking effect of current reversal on arc motion, and the arc extinguishing ability is strongest at 240 mT and 16 A. In addition, the simulation results are consistent with the experimental results. The arc-extinguishing ability of the non-polar low-voltage Dc circuit breaker is the strongest in the appropriate magnetic field, and the smaller the current is, the strongest arc extinguishing ability.

Series Arc Fault Detection Method Based on Improved MobileNet

ZHENG Li, BAO Guanghai

2024, 0(2):  13-20.  doi:10.16628/j.cnki.2095-8188.2024.02.003

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A series arc fault detection method based on an improved lightweight network MobileNet is proposed to adress the unsatisfactory detection performance of series arc faclts with noulinear loads and complex combination loads. According to the asymmetric distribution of magnetic flux, the neutral and phase lines are simultaneously passed through the current transformer to obtain the high-frequency current coupling signals. By simulating a large number of arc fault experiments in the laboratory, various arc fault samples are obtained for 7 types of loads specified in the national standard and 5 types of loads commonly used in household appliances. Data augmentation is used to generate datasets for training and testing. Finally, the arc fault detection network model is mounted on the arc fault protection prototype for online detection testing.The experimental results show that the proposed method can effectively identify series arc faults and is conducive to the productization of arc fault protectors.

Arc Fault Detection Method Based on Whale Optimization Algorithm to Improve Random Forest

ZHU Hai

2024, 0(2):  21-27.  doi:10.16628/j.cnki.2095-8188.2024.02.004

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Based on the wide variety of appliances, it is difficult to detect similar current waveforms when different appliances experience a fault arc, which can easily lead to misoperation and rejection of protection. A arc fault detection method based on whale optimization algorithm (WOA) to improve random forest (RF) algorithm is proposed. According to the national standard GB14287.4—2014, a arc fault experimental platform is independently designed and built to collect fault arc signals and extract feature values. Introducing an improved WOA to intelligently optimize and solve RF parameters. Comparing the experimental results of the classical random forest algorithm, a total of 320 sets of normal fault data from seven load combinations are collected for experiments. The experimental results show that the recognition effect of the optimized model is better than that of the classical random forest algorithm, and it can effectively diagnose arcs fault.

Simulation Analysis of Fast Transient Overvoltage in GIS Under Mayr Arc Model

YANG Fan, GAO Youhua

2024, 0(2):  28-32.  doi:10.16628/j.cnki.2095-8188.2024.02.005

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When the disconnector in SF₆ gas insulated switchgear (GIS) is used to open and close the busbar, a very fast transient overvoltage (VFTO ) with high amplitude and extremely fast rise rate is generated, which threats the insulation of GIS and adjacent equipment.The testing circuit of an 800 kV GIS disconnector switching on and off busbar is selected as the research object.The electromagnetic transient program (EMTP/ATP) is used for modeling and simulating, the Mayr arc model is used when the disconnector is ignited, and its influence on VFTO is analyzed.The voltage waveforms of the disconnector, circuit breaker side disconnector and transformer side disconnector considering the Mayr arc model are obtained,compared with the VFTO considering the time-varying resistance model. Discrete Fourier analysis of VFTO waveform is carried out to obtain the variation characteristics of overvoltage frequency and amplitude, and the research results provide a reference for GIS insulation design.

Research & Analysis

Discontinuous Pulse Width Modulation Suitable for Vienna Rectifier

ZHUANG Qingxu, LIU Haixun

2024, 0(2):  33-38.  doi:10.16628/j.cnki.2095-8188.2024.02.006

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With its advantages of high power density and high reliability, Vienna rectifier is widely used in communication power supply and electric vehicle charging and other high-voltage high-power situations. In order to realize the power factor correction (PFC) circuit characteristics of Vienna rectifier, the AC side current should be controlled as a sine wave with the same frequency and phase as the grid voltage to reduce the zero crossing distortion of the current. To further improve the power density of Vienna rectifier, switching losses should be reduced as much as possible. From the perspective of space vector,the space vector modulation strategy applicable to Vienna is analyzed. According to different control targets, discontinuous pulse width modulation (DPWM) is proposed to reduce the maximum switching loss and the zero crossing distortion of the current. Finally, the two proposed DPWM strategies are compared with SVPWM strategy through simulation. The feasibility and superiority of the two proposed DPWM strategies are verified.

Research on TCM Control Strategy of Single-Phase Inverter Based on GaN

CHEN Yu, ZHOU Baoding

2024, 0(2):  39-43.  doi:10.16628/j.cnki.2095-8188.2024.02.007

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Gallium nitride (GaN) high electron mobility transistor (HEMT) has the advantages of fast switching speed and low device loss, and is widely used in high frequency applications. In order to further improve the efficiency and power density of the converter, the triangle current mode (TCM) modulation is applied to the single-phase inverter based on GaN device.The full range zero voltage switching (ZVS) is realized by controlling the negative current and dead time, so as to improve the efficiency and power density of the converter. A prototype is built for verification. The experimental results show that TCM modulation can achieve soft switching under different load conditions. The maximum switching frequency can reach 300 kHz, and the peak efficiency can reach 98.5%.

Multiple Proportional Resonant Control Strategy of 400 Hz Single-Phase Voltage Source Inverter

YUAN Guoqing

2024, 0(2):  44-49.  doi:10.16628/j.cnki.2095-8188.2024.02.008

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A single voltage loop multiple proportional resonance (PR) control strategy is proposed to address the difficulties of proportional integral (PI) controllers in achieving zero static error control of output voltage and low order harmonic suppression.The characteristics of the PR controller is analyzed, a design method for PR parameters is provided, the simulation verification using MATLAB is finished, and the experimental verification on a 2 kVA prototype is conducted. The results show that the proposed strategy can achieve the complete elimination of specific harmonics, the total harmonic distortion of output voltage less than 1%,and the good steady-state and dynamic performance.

Detection & Text

Research on Optimization of Maintenance Interval of Urban Rail Vehicle Relay

SUN Hongliang, SU Dan

2024, 0(2):  50-55.  doi:10.16628/j.cnki.2095-8188.2024.02.009

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A method for estimating the average number of relay actions under the condition of no failure data is proposed to address the issue of limited failure data generated during the actual operation of urban rail vehicle relays, which is difficult to analyze their lifespan using commonly used parameter evaluation methods such as Weibull analysis. Furthermore, using the binomial distribution parameter estimation and actual reliability requirements the reliability life of relays under actual operating conditions is evaluated, and the maintenance interval is optimized.The feasibility and effectiveness of the proposed method is proved through examples. The application of the proposed method can effectively reduce operation and maintenance costs while ensuring the safe and reliable operation of rail vehicles, and improve the level of operational economy.

Research on Fault Diagnosis Method of High Voltage Circuit Breaker Based on Convolution Prototype Network

SHA Haoyuan, LIU Pei, WANG Zhihe, SUN Yi, ZHAO He, DENG Kai, ZHU Chao

2024, 0(2):  56-65.  doi:10.16628/j.cnki.2095-8188.2024.02.010

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Aiming at the problem that unknown samples cannot be effectively distinguished in existing circuit breaker fault diagnosis research, a circuit breaker fault diagnosis algorithm based on the convolutional prototype network is proposed. Firstly, the classification function is constructed using the clustering approach and the probability space is divided based on the distance constraint of the prototype sample point feature space for various types of faults, which can achieve the recognition of a sample set containing unknown fault classes. At the same time, with each type of prototype sample points as the cluster center, the sample feature space distance is used as the optimization target of the convolution feature self-extraction network, which can effectively improve the intra-class aggregation and inter-class dispersion of fault sample features and improve the classification accuracy of the model. Finally, the validity and accuracy of the proposed algorithm are verified based on the field experiment data of 110 kV circuit breaker. The results show that the proposed algorithm can accurately distinguish the unknown faults in the test samples and effectively improve the spatial distribution of fault sample features.

Life Prediction Method of Electromagnetic Contactor Based on Overtravel Time Degradation Characteristics

CHEN Sheng, LIU Liang, SUN Kaige

2024, 0(2):  66-71.  doi:10.16628/j.cnki.2095-8188.2024.02.011

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Starting from the failure mechanism of contactors, a detailed analysis of the overtravel time degradation process is conducted through the finite element and dynamic simulation. A life prediction method for electromagnetic contactors based on the overtravel time degradation characteristics is proposed. A life prediction model for electromagnetic contactors based on the overtravel time degradation characteristics is established. A reliability testing platform for contactors is designed and built. The remaining life of contactors is analyzed and predicted based on SJD-10048NK electromagnetic contactor testing data with a relative error of about 10%. The effectiveness of the proposed method is verified. The results indicate that the proposed method can accurately predict the life of contactors, which has important guiding significance for the reliability status evaluation and maintenance management of contactors.

Application

Location and Restoration of Single-Phase-Grounding Fault in Distribution Network Based on Feeder Terminal Unit

PENG Junlin, SHI Yong, YU Zhe, ZENG Xianfeng, DU Jun

2024, 0(2):  72-78.  doi:10.16628/j.cnki.2095-8188.2024.02.012

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The most common fault in distribution networks is grounding fault. To accurately detect and isolate grounding fault lines and restore power supply as soon as possible, a single-phase grounding fault location and recovery method based on distribution switch monitoring terminal (FTU) is proposed.Using the wavelet packet transform transient line selection and phase current transient characteristic line selection technology of FTUs at each node of the distribution network, combined with the fault path adaptive processing control strategy, and coordinating the delay closing logic of the first switch, the multi branch distribution network fault localization and automatic isolation recovery can be achieved. The proposed method can quickly select faulty lines and isolate faulty sections, which is conducive to the rapid elimination of faults and improves the safety and reliability of system operation.