Table of Content

30 April 2022, Volume 0 Issue 4

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Research & Analysis

Improved Gray Model Based on Firefly Algorithm Optimization Method for Relay Storage Life Prediction

CHEN Kangning, WANG Zhaobin, LI Zhen, QIAO Qingyun

2022, 0(4):  1-5.  doi:10.16628/j.cnki.2095-8188.2022.04.001

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Aiming at the problem of contact resistance prediction and prediction accuracy of missile relays,a new gray model based on the firefly algorithm (FA) optimized and improved gray model is proposed.On the basis of the traditional gray GM(1,1) model,the model is dynamically updated using the equal-dimensional gray number recursive method to establish an improved gray model RGM(1,1),and the firefly algorithm is introduced to optimize its weight parameters,and get new model RFGM(1,1),the RGM(1,1) model and the RFGM(1,1) new model are used to predict the trend of contact resistance.After a comparative analysis of the prediction results,it shows that the new model has a higher prediction Accuracy.

Equivalent Modeling Method of SiC MOSFET Based on Graphical Modification

WANG Zicheng, LAI Yaokang, WANG Haonan, CAO Yufeng, YE Xuerong, ZHAI Guofu

2022, 0(4):  6-11.  doi:10.16628/j.cnki.2095-8188.2022.04.002

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Accurate SPICE model of SiC MOSFET will play an important role in product simulation and testing.A modeling method of SiC MOSFET is introduced.The spice model of CPM3-0900-0010A is established and modified by combining automatic fitting with graphic correction technology considering physical meaning.The established model characteristic curve fits well with the measured curve provided by the product parameter manual.The key parameters generated in the modeling process are more consistent with the parameters provided in the product parameter manual,which improves the preciseness and accuracy of the simulation model.Compared with the actual test results,the fitting effect of the model is good,which can provide the basis for the simulation method of complex circuit with SiC MOSFET,and provide support for more accurate evaluation of the performance and system characteristics of SiC MOSFET.

Research on Control Strategy of Vienna Rectifier Under Unbalanced Grid Condition

HE Chen, HUANG Haihong

2022, 0(4):  12-18.  doi:10.16628/j.cnki.2095-8188.2022.04.003

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When the grid voltage is unbalanced,the original control strategy will generate a large amount of third harmonic current,and the stability of the rectifier operation in Vienna will be seriously affected.Based on the analysis of the causes of rectifier operation power pulsation when the grid voltage is unbalanced,the quasi-PR regulator control strategy is applied to inject an appropriate amount of negative sequence current into the grid side to suppress the active power and DC side voltage pulsation.The algorithm can separate the grid phase sequence precisely and quickly,which makes the control of the system faster.Finally,the feasibility of the control strategy is verified by MATLAB/Simulink.

Improved Single-Cycle Control Based on Linear Active Disturbance Rejection

WAN Lufeng, XU Yuzhen

2022, 0(4):  19-27.  doi:10.16628/j.cnki.2095-8188.2022.04.004

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Taking a high gain boost Cuk converter with scalable unit as the research object,an improved single-cycle control strategy based on linear active disturbance rejection is proposed.A control method combining linear active disturbance rejection control strategy and single-cycle control technology is adopted to solve the problem that the single-cycle control technology has limited effect on the nonlinear characteristics and time-varying disturbance of Cuk converter when it is disturbed by the system.Compared with other control methods,the stability of large signal and the rapid recovery performance in case of disturbance is ensured.The simulation and experimental results show that the proposed control strategy can suppress the system disturbance more effectively and make the system more robust than the traditional single-cycle control.

Research on Triboelectric Magnetic Energy Harvester Based on Magneto-Mechano-Electric Effect

SUN Tianzi, ZHAI Xiaoshe, GENG Yingsan, ZHANG Gaochao, WANG Xiaohua

2022, 0(4):  28-34.  doi:10.16628/j.cnki.2095-8188.2022.04.005

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A triboelectric magnetic energy harvester structure is proposed based on the abundant and widely distributed magnetic energy in power systems.By building a magnetic energy harvesting test platform,the electrical output performance of the magnetic energy harvester is tested and analyzed in terms of magnetic field strength,material thickness,and environmental humidity variation.The experimental results show that the output voltage and current of the magnetic energy harvester increase with the increase of magnetic field strength,and the maximum instantaneous output power increases from 846 μW to 4 400 μW,which increases the output power by 4.2 times.With the decrease of PDMS material thickness,the output open circuit voltage and short circuit current of the magnetic energy harvester increase first and then decrease.With the increase of relative humidity,the output open-circuit voltage and short-circuit current of the triboelectric magnetic energy harvester both show a decreasing trend.

Research on Reliability Investment of Distribution Network Based on Combination Weighted Grey Correlation Analysis

WANG Xiaodong, FEI Ke, SHA Yuchen, HOU Siwei

2022, 0(4):  35-40.  doi:10.16628/j.cnki.2095-8188.2022.04.006

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Aiming at the problem that the traditional grey correlation analysis method adopts the equal weight treatment method for each influencing factor when solving the grey correlation degree,and does not consider the different influence degree of historical data on the existing situation with the growth of years,a combined weighted grey correlation analysis method is proposed.Based on the reliability historical data of a region,the key factors affecting the power supply reliability are determined,and the correlation equation between the reliability index and the key factors is established.The improvement value of reliability index is decomposed into the improvement objectives of key influencing factors,and the total investment to achieve the reliability objectives is obtained according to the investment calculation model of typical engineering scenarios.The example shows that the method proposed has certain advantages over the traditional method,which can reduce blind investment,improve the use efficiency of Engineering funds and achieve accurate investment.

Electrical Design & Discussion

Design of Multifunctional Electronic Load Based on Active Power Filter

LI Xinyuan, GAO Peng, YU Haoran, SHEN Zhendong, WANG Baichao, LIN Yan

2022, 0(4):  41-46.  doi:10.16628/j.cnki.2095-8188.2022.04.007

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In order to solve the load problem of in-factory commissioning and factory inspection of power quality governance products,a multifunctional electronic load based on active power filter (APF) is proposed.The load consists of two APFs and a transformer.The two APFs adopt different control strategies.Switching the working mode of the device through monitoring,the active power,reactive power,harmonic,interharmonic and unbalanced currents are generated,and the flexible adjustment and control can be achieved.Simulation and experiment verify the feasibility and effectiveness of the device.

Short-Circuit Current Fast Identification Device for MVDC System

JU Xingbao, WANG Wei

2022, 0(4):  47-54.  doi:10.16628/j.cnki.2095-8188.2022.04.008

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In order to improve the stability and reliability of DC system and ensure that the short-circuit current can be judged and cut off in time after the failure of DC system,a short-circuit current fast identification device for medium voltage DC(MVDC) system is proposed.The hardware is designed with the dual processor structure of FPGA+AVR as the core of each functional circuit,which realizes the extraction and conditioning of the main circuit current,as well as the communication,human-machine interaction and communication functions between the two processing chips.The software system of the short-circuit currnt identification device is projected respectively using top-down and modular programming ideas for FPGA and AVR.The short circuit current fast identification software system based on DDL algorithm,FIR filter and sampling algorithm is designed.Finally,the rapid and accurate identification of the short-circuit current by the device is verified through experiments,which provides a guarantee for the stable operation of MVDC system.

Analysis on High-Voltage Fuse Abnormal Fusing of 10 kV Potential Transformer in Internet Data Center

YANG Yang, SHI Guifeng, XU Xianqing

2022, 0(4):  55-59.  doi:10.16628/j.cnki.2095-8188.2022.04.009

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In order to investigate the high-voltage fuse frequent fusing of 10 kV secondary cabinet V-V connection potential transformer (PT) in internet data center,the steady-state power quality of the system is tested,and the voltage and current signals of the PT are recorded and analyzed for a long time.The excitation characteristics of the PT are tested on site to eliminate the causes of ferromagnetic resonance and product quality.The fuse was dissected.Combined with the time characteristic curve of the fuse,it is preliminarily inferred that the reason for PT fuse fusing is that the primary fuse is damaged and fused gradually due to frequent impact of disturbance current.Finally,the monitoring data of the PT with the fuse specifications of 1A and 2A are compared and analyzed,and the solution to replace the 1A fuse with 2 A at this stage is proposed.Then,the suggestions are put forward for further troubleshooting.

Design of External Residual Current Circuit Breaker for Self-Checking and Self-Restoring Electric Energy Meter

ZHAO Ce, ZHENG Yuanchang

2022, 0(4):  60-64.  doi:10.16628/j.cnki.2095-8188.2022.04.010

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The external residual current circuit breaker the for with the checking and self-restoring function is proposed.The principle and hardware design of checking and self-restoring are analyzed in detail.The difficulty that the residual current protection of traditional products may not be inspected regularly in practical application is solved,and the safety and reliability of products are improved.

Influence of Contact Welding Surface Structure on Electric Contact Brazing Quality

LI Li, ZHOU Haiming, GAO Yubao, ZHANG Yang, WANG Yuehua, BIAN Jian

2022, 0(4):  65-69.  doi:10.16628/j.cnki.2095-8188.2022.04.011

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From the actual production of brazed electrical contacts in the field of low voltage electrical apparatus,the principle is analyzed for the frequently unqualified products combined with the ultrasonic testing and metallographic diagrams.It’s determined that the major reason for the unqualified product brazing rate is that the contact grid-like welding surface structure is not conducive to the spreading,wetting and interaction of the liquid solder to the base metal.The four different welding surface structure design contacts for brazing used.After welding,the appearance,brazing rate,metallographic structure and shear strength of the electrical contacts are compared and analyzed.The results show that the welding effect of striped contacts on welding surface is better than that of flat contacts and grid contacts.The shear strength range is (140.1±3.6) MPa,and the brazing rate range is (95.11±3.66)%.

Distribution System Technology

Evaluation and Analysis of Uninterrupted Operation Capacity in Distribution Network Based on AHP-Delphi Method

WANG Qingze, ZHANG Shouqiang, AI Maomin, WANG Jia, ZHANG Shuo

2022, 0(4):  70-75.  doi:10.16628/j.cnki.2095-8188.2022.04.012

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Uninterrupted operation in distribution network is an important technical hand to improve the reliability of power supply. In order to continuously improve the uninterrupted operation capacity in distribution network, explore and analyze the influencing factors of uninterruptible operation capacity in distribution network, and accurately find out the key factors,the evaluation and analysis method of uninterruptible operation capacity in distribution network based on the analytic hierarchy process(AHP)-Delphi method is proposed.Firstly,the influencing factors of uninterrupted operation capacity in distribution network are listed,and the hierarchical evaluation index system of influencing factors is constructed.Then,the judgment matrix is constructed by Delphi method and AHP is used to calculate and analyze,and the weight coefficient of influencing factors is output to provide the basis for the decision-makers to implement policies accurately.Finally,combined with the status of uninterrupted operation capacity in distribution network in a certain area,it is verified and analyzed.The results show that the method can accurately judge the importance of the influencing factors,accurately and efficiently use existing resources,improve the ability of uninterrupted operation capacity in distribution network continuously,and maximize the overall benefits.

Fault Simulation of DC Distribution Network with Distributed Power Access

LI Jiaxu, XIA Hua, BAO Xiangyu

2022, 0(4):  76-82.  doi:10.16628/j.cnki.2095-8188.2022.04.013

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The power access requirements and the topology of modular multi-level converters in the multi-terminal flexible DC distribution network,are introduced.The scope of protection required in the multi-terminal flexible DC distribution network is clarified.The typical faults in each protection area are analyzed theoretically.According to the equivalent circuit diagram after each failure,the current and voltage characteristics are numerically calculated.Based on the actual engineering construction of a three-terminal flexible DC distribution network simulation model,the faults in eacharea are simulated and verified.

Research on Control Strategy and Consumption Capacity Evaluation of Distributed Generation Access to Distribution Network

WANG Yunhui, ZHENG Qiangren, GUO Miao, XIAO Huanchun, HE Houdao, CHEN Wanxi

2022, 0(4):  83-87.  doi:10.16628/j.cnki.2095-8188.2022.04.014

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Due to its own advantages,distributed generation (DG) is mainly connected to medium and low voltage distribution network.Large scale access has many impacts on distribution network.DG grid connection structure and control technology are greatly different from the traditional power generation methods.By analyzing the impact of DG access to distribution network, starting from the control of distribution network after grid connection,the surrounding load is coordinated and the five control strategies for distribution network planning and voltage level are summarized.From the capacity of the selected access location,its acceptance capacity is analyze by evaluating the consumption level after access,and the improvement measures are summarized.Finally,taking a regional distribution network as an example,a model is established for calculation and analysis,which not only solves the consumption problem after access,but also improves the overall energy utilization rate and improves the stability and flexibility of the power grid operation.