Table of Content

30 August 2021, Volume 0 Issue 8

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Research & Analysis

Influence of Contact Rotation and Breaking on Electric Field Between Electrodes in Vacuum

LIU Jiajia, CAO Yundong, FU Si

2021, 0(8):  1-5.  doi:10.16628/j.cnki.2095-8188.2021.08.001

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This paper established a physical model of the space charge distribution between the contacts in the rotary breaking mode.Based on the Poisson equation,the finite element analysis method is used to calculate the electric field distribution between the contacts when the contacts rotate at different angles.The intensity change and the extreme value of the spatial electric field intensity are used to analyze the influence of the rotating motion of the contact on the electric field between the contacts during the breaking process in a vacuum state,and the reasons for the electric field intensity change between the contacts are explained from a microscopic point of view.The research results show that the rotating motion of the contact helps increase the space charge distribution area,reduce the distortion effect of the space charge on the external electric field,and reduce the extreme value of the space electric field.

Research on Digital Precision Measurement Technology and Micro-Breaking Performance Improvement of Miniature Circuit Breaker

YANG Wenqiang, ZHANG Baoliang, ZHANG Penghe, YUAN Xuebing, ZHAO Hu

2021, 0(8):  6-10.  doi:10.16628/j.cnki.2095-8188.2021.08.002

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In this paper,the digital precision measurement techniques such as laser shadow technology,laser light-filling high-speed photography and splitter voltage measurement system are used to quantitatively analyze the miniature circuit breaker(MCB) arc behavior and parameter of arc starting,arc root transfer and splitter voltage in the short-circuit breaking.By analyzing the arc motion behavior,the factors affecting the arc motion are diagnosed and the precise optimization scheme is provided.A certain type of YL miniature circuit breaker was taken as an example.Firstly,the parameters of arc motion are measured by digital precision,and then through diagnosis and analysis,two optimization schemes of optimizing arc starting angle and enlarging arc starting plate are given.Through improvement and optimization,the breaking capacity of the miniature circuit breaker is rapidly improved.The above results show that the digital precision measurement technology can provide a rapid precision diagnosis for the improvement of the breaking performance of the miniature circuit breaker,and has great practical significance in engineering.

Influence of Contact Welding Process on Performance of Low Voltage Circuit Breaker

LI Ziqi, CHEN Yinbing

2021, 0(8):  11-15.  doi:10.16628/j.cnki.2095-8188.2021.08.003

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As the core component of low voltage circuit breaker,electrical contact bears the role of connecting,loading and breaking current in the circuit,and its performance directly affects the service life and safety of related equipment.The ideal electrical contact should meet the requirements of high breaking capacity,strong arc resistance,good welding resistance and low temperature rise.This paper analyzes the important influence of contact welding process on the performance of low voltage circuit breaker based on the fixed mode of electric contact and the relevant tests in the design and certification process of low voltage circuit breaker.At the same time,some reasonable suggestions are put forward for the contact welding in the manufacturing process of low voltage circuit breaker.

Research on Power Information Network Security Situation Awareness Based on LDA-RBF

ZHANG Xiaofei, ZHANG Daoyin, ZHENG Luolin, CHEN Decheng, FU Rong

2021, 0(8):  16-23.  doi:10.16628/j.cnki.2095-8188.2021.08.004

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To accurately predict the security situation of power information network,a network security situation awareness method based on machine learning is proposed.In this method,the network security situation awareness is abstracted as a numerical quantization problem,and a large number of test samples are used as data sources to input the situational awareness model to characterize the perceived results.Based on the linear discriminant analysis (LDA),the test data is preprocessed to optimize the sample data to obtain combined features and find out the best projection.Then the processed data are used as input of RBF neural network to find the nonlinear mapping relation of the network situation value,and the network security situation is quantified.Finally,the effectiveness of the proposed method in the security situation analysis is verified through KDD Cup99 dataset and the cyber attack data in the power information network.

Research on Load Curve Shape Clustering Based on Variance Comparison

YAN Kun, GAN Jingfu, TIAN Xincheng, HE Pengkang, MA Minhan, HE Chen

2021, 0(8):  24-30.  doi:10.16628/j.cnki.2095-8188.2021.08.005

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The traditional load curves clustering method is generally based on Euclidean metric,but the curves with different shapes can have the equal Euclidean metric relative to the same clustering center.Therefore,the Euclidean metric based clustering method can not accurately classify the curves in morphology.Aiming at the this shortcomings,an adaptive shape clustering algorithm based on discrete curves variance comparison is proposed.The proposed method takes the variance of the difference between the load curve and the clustering center as the basis,to realize the classification based on the curve shape.In this paper,the principle and shortage of Euclidean metric based clustering method are analyzed,then the basic principle of shape clustering based on variance comparison and its corresponding clustering center updating method are detailed related.Based on the simulation and the actual examples,theses two clustering method are analyzed and compared with each others.The results show that the variance comparison based clustering algorithm has better performance on shape classification,the feasibility and validity of the proposed method are verified by the final analysis results.

Electrical Design & Discussion

Design of In-situ Analysis System of Characteristic Parameters for Electrical Connector

MENG Yuan, REN Wanbin

2021, 0(8):  31-35.  doi:10.16628/j.cnki.2095-8188.2021.08.006

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In order to simulate the real service conditions and obtain the degradation data of electrical connector,a test rig for in-situ analysis characteristic parameters of electrical connector is designed.The repetitive insertion and withdrawal test and the continuous ohmic heating test could be carried out under the setting temperature,humidity and fretting environment.Meanwhile,the contact resistance,mechanical force,insulation resistance and other characteristic parameters could be recorded simultaneously with the help of designed multi-channel signal measurement and control circuit and programmed software.It is valuable for the recurrence of the failure phenomenon and the study of failure mechanism of electrical connectors.

Optimizati on Design of Contactor Vibration Index Based on Finite Element Analysis

WANG Jianxiong, XIAO Bin

2021, 0(8):  36-39.  doi:10.16628/j.cnki.2095-8188.2021.08.007

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The application fields,such as aeronautics and astronautics,require high performance of contactor in vibration and other endurance environment.In this paper,the optimization design of the contactor vibration index is studied.Through the finite element simulation calculation,the weak points in the structure of the auxiliary contact components of the contactor are obtained,and the improvement direction and expected improvement effect are determined through the virtual prototype simulation,which provides a theoretical basis for the optimal design of the contactor vibration index.According to the calculation results,the vibration index of the contactor is improved obviously,which fully demonstrates the effectiveness of the optimization design method.The performance of the optimized product is obviously improved,which can meet the needs of use.

Experimental Study on Terminal Block Temperature Rise of Miniature Circuit Breaker

HUANG Jia, REN Changbin, ZHANG Yanyang

2021, 0(8):  40-42.  doi:10.16628/j.cnki.2095-8188.2021.08.008

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The terminal temperature rise of miniature circuit breaker is not only the main performance in product development and design,but also an important parameter for fire prevention,which has an important impact on the actual use of products.Among them,the current size,wire type and specification,structure design of wiring frame,tightening torque and so on are important factors affecting the temperature rise of terminal.This paper mainly compares the terminal temperature rise under different influence factors through experiments,and obtains some important conclusions.

Distributed Generation and Grid-Connection Technology

Optimal Dispatch of Micro Energy Grid Based on Exergy Efficiency

CHENG Jiawei, MU Longhua, LIANG Ziwen

2021, 0(8):  43-50.  doi:10.16628/j.cnki.2095-8188.2021.08.009

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Micro energy grid can provide multiple types of energy such as cold,heat,and electricity,making it possible to integrate and dispatch the various kinds of energy resources.Exergy analysis shows the efficiency of different types of energy in two aspects of quantity and quality.Based on the exergy theory on the basis of the second law of thermodynamics,this paper analysed exergy of the whole system and then established a micro energy grid scheduling model with exergy efficiency maximization as the optimization goal in order to improve energy utilization,and solve the model with particle swarm optimization algorithm.Using an example to verify the proposed optimization scheduling model can reveal the utilization of energy accurately,and realize the transformation of energy evaluation index from quantity characteristic to quality characteristic.

Photovoltaic Power Prediction Method Based on Improved Long Short Term Memory Network and Gaussian Process Regression

DENG Weiji, XIAO Hui, LI Jinze, WANG Jiaqi, LU Wentao

2021, 0(8):  51-57.  doi:10.16628/j.cnki.2095-8188.2021.08.010

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In order to obtain accurate photovoltaic power prediction results and quantify its uncertainty,a photovoltaic power prediction method based on improved long-term memory network (LSTM) and Gaussian process regression (GPR) is proposed.Firstly,in order to reduce the variables that need to be optimized,the structure of LSTM is improved.Then,the optimal characteristic variables obtained by genetic algorithm are combined into the improved LSTM to get the first point prediction result.Then,the first point prediction result and the actual value are combined with GPR to get the final prediction result with probability significance.Finally,taking Zhujia photovoltaic power station in Hunan Province as an example,the simulation results show that compared with other methods,this method can obtain high-precision,suitable prediction interval and strong reliability prediction results in a short time,which proves that this photovoltaic power prediction method can take into account both accuracy and reliability,and has a certain practical engineering significance.

Adaptive Two-Stage Droop Control Method for Islanded DC Micro-grids

LIU Wenliang

2021, 0(8):  58-63.  doi:10.16628/j.cnki.2095-8188.2021.08.011

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An adaptive two-stage droop control method is proposed for islanded DC micro-grids.A time-delay feedforward path is deployed in the droop relation,through which the system can maintain economic operation by meeting the equal incremental cost principle while restoring the DC bus voltage adaptively at the same time.Detailed small-signal analysis is conducted to illustrate the impacts of different control parameters on system stability.In addition,two plug-and-play strategies are presented to enhance the system robustness and reliability,one with full autonomy and one with distributed communication.Finally,the simulation results verify the effectiveness of the proposed control method.

Research on Pulse Width Modulation Strategy of High Power Two-level Voltage Source Inverter

XU Dong, WANG Ying

2021, 0(8):  64-69.  doi:10.16628/j.cnki.2095-8188.2021.08.012

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ing at the problem caused by low switching frequency of power devices in high-power two-level voltage source inverter,a multi-mode PWM strategy with asynchronous space vector pulse width modulation (SVPWM) in low frequency and synchronous SVPWM and specific harmonic elimination pulse width modulation (SHEPWM) in medium frequency is proposed.This modulation strategy can avoid the problems of excessive storage of SHEPWM switching angle at low frequency and high harmonic voltage content at medium frequency.The voltage vector equivalent method is used to realize the smooth switching between SHEPWM and SVPWM,and the current harmonic zero crossing method is used to realize the smooth transition between SHEPWM.different carrier ratios of MATLAB/Simulink is used to build the simulation platform to verify the feasibility of the multi-mode PWM strategy.

Design of Energy Storage Power Converter

WANG Xiaoping, CHEN Yanlian, MAO Xingkui

2021, 0(8):  70-75.  doi:10.16628/j.cnki.2095-8188.2021.08.013

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The charge discharge switching control and parameter design of energy storage PCS (Power Conversion System) are of great significance to optimize the performance and efficiency of energy storage system.Aiming at the problems of high reactive power and serious current distortion in charge discharge switching of PCS,a linear soft switching method based on single current loop decoupling control is proposed.Firstly,the mathematical model of energy storage PCS is established,and the decoupling control block diagram of single current loop is designed.Secondly,the problems of current distortion and impact in charging and discharging switching of energy storage PCS are analyzed.The control strategy of charging and discharging soft switching by changing the direct axis current command linearly is proposed,and the key hardware parameters and software program block diagram are designed.Finally,a 12 kW bidirectional PCS prototype is built according to the designed parameters,and the correctness of the parameter design and the effectiveness of the linear soft switching control strategy are verified by experiments.

Development of Fast Power Control Device for Grid Connection Point of new Energy Station

BAI Shenyi, YU Gaowang, YANG Guixing, XU Shenglong, WEI Yanwei

2021, 0(8):  76-81.  doi:10.16628/j.cnki.2095-8188.2021.08.014

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In order to make full use of the primary frequency regulation capability of new energy stations,a fast power control device suitable for grid connected operation of new energy stations is developed.Firstly,the function of the device is introduced,the hardware and software design scheme is proposed,and then the fast power control strategy flow is analyzed.The device supports IEC 103,Modbus TCP and other communication protocols.UDP protocol or GOOSE communication can be used for millisecond level control of inverter to realize fast power regulation of photovoltaic station.The device integrates station AGC function design,and can receive the regulation instruction of dispatching AGC system.The test results show that the frequency measurement accuracy of the device is as high as 0.001 Hz.The whole set of action time is less than 60 ms.The response speed of new energy fast power regulation is significantly improved.

Application

Application of Energy Fusionsystem Based on LoRa and Edge Computing

CHEN Shifeng, ZHANG Jianxing, SUN Huili, XU Honggang, MA Shuai

2021, 0(8):  82-87.  doi:10.16628/j.cnki.2095-8188.2021.08.015

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With the rapid development of new energy and rechargeable vehicles,the role of adjustable load in the power system is becoming more and more obvious.When the adjustable resources mainly including energy storage and distributed photovoltaic participate in peak load shifting and valley filling of substation area distribution,it is necessary to collect the information of grid connection point,transformer,new energy and load,and carry out advanced strategy implementation.The information collections need to add metering devices and cable laying,which increases a lot cost.The energy fusion device developed in this paper adopts the Internet of things(IoT) technology,uses intelligent measurement switch to collect information,and transmits information through LoRa technology to meet the optimal control of active and reactive power,and realizes various functions such as peak shaving and valley filling,reactive power compensation,new energy consumption,orderly charging of electric vehicles etc.,and realizes localized edge calculation,which is verified by experiments.