Table of Content

30 December 2021, Volume 0 Issue 12

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Overview

Review of Relay Life Prediction Methods Based on Deep Learning

LIU Baixin, WANG Zhaobin, QIAO Qingyun, ZHU Jiamiao, LI Zhen

2021, 0(12):  1-6.  doi:10.16628/j.cnki.2095-8188.2021.12.001

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In recent years,with the continuous development of science and technology,the remaining service life of relay and other electrical components has gradually become a research hotspot.The accurate and efficient analysis of massive monitoring data is the main task of fault detection and health management.Because the traditional methods are limited to rely on the physical models and prior knowledge,the deep learning methods emerge as the times require.First,the current research status of the remaining life of relays at home and abroad is introduced.Second,it analyzes the remaining life prediction method based on deep learning in detail is analyszed,and the advantages and disadvantages of each method are summarized.Finally,the future is looked forward to.

Research & Analysis

Research on Arc-Extinguishing Performance of C4-PFN-CO₂ Mixed Gas in 145 kV Disconnecting Switch

WANG Wei, LUO Yan, HUANG Qingdan, ZHUO Ran, SONG Haoyong, WANG Dibo

2021, 0(12):  7-12.  doi:10.16628/j.cnki.2095-8188.2021.12.002

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In order to verify C4-PFN arc extinguishing ability in the 145 kV disconnecting switch and the application prospects,C4-PFN-CO₂ mixed gas is selected as the medium for the current interruption experiments.Before the experiments,the saturated vapor pressure characteristics of C4-PFN gas was studied,and the optimal mixing ratio of C4-PFN-CO₂ mixed gas was obtained under the limit of -25 ℃ liquefaction temperature.The maximum proportion of C4-PFN in the mixed gas is 5.8% at -25 ℃.Through the experiments,it can be found that at 0.6 MPa,the arc voltage of the C4-PFN-CO₂ mixed gas is lower than that of SF₆,and the amount of arc energy injection is also smaller.It shows that the energy dissipation rate of SF₆ is higher and the arc extinguishing ability is better.When the pressure increase to 0.7 MPa,the arc voltage of the C4-PFN-CO₂ mixed gas is very close to SF₆ at 0.6 MPa,and voltage spikes also appear at the start of the arc.It means that the increase of pressure can significantly improve the energy dissipation rate of the mixed gas and the arc extinguishing performance.For arc time dispersion,the increase of pressure also reduces the dispersion,which significantly improves the arc stability during the current interruption process.

Research on Constant Voltage Output MC-WPT System

YIN Yong, ZHU Lujing, WANG Chengliang, XIAO Yuhua

2021, 0(12):  13-19.  doi:10.16628/j.cnki.2095-8188.2021.12.003

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A constant voltage output magnetic coupled wireless power transfer(MC-WPT) system is designed to solve the problem that the output voltage can not be constant due to the wide input voltage range,large load fluctuation and mutual inductance variation in some special application scenarios.The system uses LCC-S type compensation topology,cascades phase-shifted full-bridge inverters and Boost converters as voltage regulation circuit,deduces the system output voltage expression,establishes the system mathematical model,designs a closed-loop controller,and achieves a constant voltage output when the system has a wide range of input voltage,large range of load and mutual inductance.The feasibility of the design scheme of this constant voltage output MC-WPT system is verified by the simulation and experiment.

Short Circuit Characteristics Analysis and Modeling on Inverter End of Energy Storage Power Station

LV Lixing, XU Feng, SUN Haoquan, DENG Huabin, JI Tongjun, CHEN Qian, ZHANG Zhengwei

2021, 0(12):  20-27.  doi:10.16628/j.cnki.2095-8188.2021.12.004

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As the intra-day peak-valley difference of grid load has further expanded,a large number of energy storage power stations have been put into operation in order to meet the needs of grid peak shaving and other requirements.Compared with the traditional power supply,the short-circuit current output characteristics of the inverter terminal have changed greatly after the fault.At present,steady-state fault models are often used for analysis and calculation,but the accuracy is not high.This paper introduces the control strategy of the inverter end of the energy storage power station under the low voltage ridethrough state,and builds a fault simulation platform.The impact of three main factors on the transient short-circuit output characteristics is compared and analyzed,and then a short-circuit current mechanism model based on voltage drop is proposed.According to the different degrees of voltage drop,the short-circuit current is modeled segmentally,and a certain algorithm is used for parameter identification.Finally,the accuracy of the built model is verified by simulation comparison.

Technical Evaluation Index System for Integrated Energy System

GONG Ping, LUO Shuqi, ZHANG Yuanxin, ZHU Yongqiang, XIA Ruihua, DUAN Chunming

2021, 0(12):  28-33.  doi:10.16628/j.cnki.2095-8188.2021.12.005

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The integrated energy system (IES) can realize the coupled utilization of multiple energy sources and meet the diversified energy demand of users.Technical evaluation of IES can help improve its energy supply capacity.First,the system energy supply and operation capability was taken as the evaluation purpose of this article,and a technical evaluation index system was established from the perspectives of energy efficiency,reliability and safety according to the characteristics of IES.Then the quantitative methods for the evaluation indices were given.Finally,taking the park-level integrated energy system as a case,the analytic hierarchy process was used to demonstrate the technical evaluation.

Multi-Energy Storage Power Station Planning Method Based on Overload Ratio of Main Transformer

YANG Jun, HUANG Jiyuan, HUANG Keli, ZENG Linjun

2021, 0(12):  34-41.  doi:10.16628/j.cnki.2095-8188.2021.12.006

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To effectively relieve the overload and peak regulation pressure of the main transformer in the power grid.A planning method of the multi-energy storage power station is proposed,which is constrained by the heavy load ratio of the main transformer.While satisfying the operating constraints of the system,this method builds an optimization objective of maximizing the net present value (NPV) of economic benefit and dynamic life cycle cost for the operating cycle of the energy storage power station to optimize the installation location and capacity of the energy storage power station as well as the installation number.The improved NSGA-Ⅱ algorithm is used to solve the problem.Finally,taking a demonstration project as an example,this planning method is used to plan multiple energy storage power stations.The simulation results show that this planning method can effectively reduce the peak-valley error rate and the overload rate of the main transformer,and improve the stable operation ability of the system.

System Design & Discussion

Comparative Study on Electrical Contact Performance of Flexible Spring Components for Electromagnetic Relays

ZHAO Zien, ZHANG Chao, REN Wanbin

2021, 0(12):  42-46.  doi:10.16628/j.cnki.2095-8188.2021.12.007

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The spring components of electromagnetic relays play a vital role in its electrical performance.In this paper,the relationship between contact force,contact position,contact area,sliding distance and the travel of push rod (or armature) is obtained by finite element simulation,and the relationship between circuit resistance,contact resistance and contact force is further analyzed.Finally,the electrical contact performances of different types of flexible spring components are compared and analyzed.

VIENNA Rectifier Midpoint Potential Fluctuation Principle and Balance Method

ZHANG Deyang, CHANG Wenjing, HUANG Haihong

2021, 0(12):  47-51.  doi:10.16628/j.cnki.2095-8188.2021.12.008

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As a kind of three-level rectifier,the mid-point potential of Vienna rectifier also has the problem of triple frequency fluctuation.Aiming at the problem of mid-point potential fluctuation,the current solutions are mainly to inject zero sequence to suppress the mid-point potential fluctuation.Firstly,this paper analyzes the principle of mid-point potential fluctuation and obtains the factors influencing the mid-point potential fluctuation and its fluctuation law.Secondly,according to the space vector modulation method,the mid-point potential control principle is analyzed,and the space vector modulation strategy is proposed.Finally,an experimental platform is built to verify the effectiveness of the proposed method.

Research on Intelligent Patrol System Based on Multi-Perception Technology

CUI Yu, WANG Ye

2021, 0(12):  52-57.  doi:10.16628/j.cnki.2095-8188.2021.12.009

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In order to ensure the safe and reliable operation of relay protection device,it is necessary to inspect the protection device regularly.In this paper,an intelligent inspection system based on multi perception technology is developed.With the help of the intelligent cabinet composed of high-definition and infrared cameras,temperature and humidity sensors,smoke sensors and other multi-perception devices installed in the front and back of the cabinet,the automatic inspection of the protection device is realized through image recognition technology and intelligent inspection and fault diagnosis technology.Firstly,the overall architecture and data flow diagram of the intelligent patrol system are introduced.Then,it focuses on the image recognition technology based on convolution neural network,which is a key technology in the inspection system.Through the construction of neural networks for different inspection items such as device appearance recognition and pressing plate recognition,the abnormal equipment and circuit can be identified.The recognition accuracy of all items is above 96%,and the effect is good.Furthermore,it introduces another key technology in the inspection systemintelligent inspection and fault diagnosis technology,introduces its working principle,and gives an example of inspection and fault diagnosis.The intelligent inspection system based on multi-sensor technology lays a foundation for the realization of unmanned or few people inspection of relay protection.

Design of High Efficiency Wireless Charging System for UAV Based on Lightweight Magnetic Coupling Structure

CHEN Shaonan, CHEN Qianyi, GAO Like, CHEN Jin, LIANG Guangsheng

2021, 0(12):  58-63.  doi:10.16628/j.cnki.2095-8188.2021.12.010

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Because of its high efficiency and convenience,unmanned aerial vehicle (UAV) patrol inspection has become an important trend in the field of electric power patrol.The short range of UAV patrol inspection seriously restricts the work radius of UAV.The charging autonomy and intellectualization of UAV can be greatly improved by wireless power transfer (WPT).Firstly,the anti-offset performance of coil structures with different shapes is studied comparatively.And the range of mutual inductance of the coupling structure is obtained by analyzing the voltage and current constraints of system.Secondly,the coupling structure is optimized with the aim of lightweight pickup based on the parametric scanning function of COMSOL finite element simulation software.Finally,a WPT system based on the optimized coupling structure is built with efficiency of 91%,which is in good agreement with the theoretical analysis.

Focus Bypass Type Parallel UPS Phase Lock Method

SHI Wei, ZHAO Qiliang

2021, 0(12):  64-66.  doi:10.16628/j.cnki.2095-8188.2021.12.011

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In order to solve the problem that focused bypass type parallel UPS system phase-locked control complex,and low precision,according to the theory analysis and engineering conditions,this paper puts forward a second order phase locked control method and the control precision and harmonious wave characteristics are analyzed in detail.The experimental results show that the proposed method is simple and can effectively improve the synchronization control precision of parallel UPS system,which can restrain the circulation and ensure the stable operation of parallel UPS system.

Distribution System Technology

Grid Division Principle of Medium Voltage Distribution Network Based on Planning Difference

XUAN Jingyan, CUI Hongbo, LI Qin, QI Yibin

2021, 0(12):  67-70.  doi:10.16628/j.cnki.2095-8188.2021.12.012

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Based on the three-level division of power supply area,grid and power supply unit,this paper describes and analyzes the difference planning and non difference planning of medium voltage distribution network,studies the principle of grid division,and explains that the grid division of medium voltage distribution network should be based on the masching the capacity difference of planning unit (substation and line unit) and the load density difference.Through the actual grid planning application in a certain area,it is proved that the grid division principle proposed in this paper is very reasonable.

Flexible Grounding Arc Suppression Method of Distribution Network Based on Discrete Domain Double Closed Loop Control

LU Yang, PAN Yifan, YANG Yajun, WU Jiaheng

2021, 0(12):  71-77.  doi:10.16628/j.cnki.2095-8188.2021.12.013

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When a single-phase grounding fault occurs in a neutral point non-effectively grounded distribution network,the traditional arc suppression coil can only compensate for the reactive components of the grounding current,but not the active and harmonic components.In this paper,by analyzing the mechanism of active arc suppression for single-phase grounding faults,an active arc suppression method based on double closed-loop control in the discrete domain is proposed.The inner current loop provides virtual damping for the system,and the optimal gain design method of the current inner loop is proposed based on root locus analysis.The voltage outer loop adopts a resonant controller to realize the non-static adjustment of the AC voltage,and a delay compensation method is proposed to improve the stability of the system.The simulation results verify the effectiveness of the proposed discrete domain double closed-loop control strategy.When a single-phase grounding fault occurs in the distribution network,the ground current can be fully compensated to ensure the safe and reliable operation of distribution network.

Restoration Method for Distribution Networks Considering Distributed Generators

FENG Yi, JIN Bin, CHEN Na, ZHANG Hui

2021, 0(12):  78-84.  doi:10.16628/j.cnki.2095-8188.2021.12.014

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Due to the volatility of power supply,more uncertain factors need to be considered in the recovery of distribution network failures.Therefore,this paper proposed a fault recovery method that considers the uncertainty of distributed power output.First,based on the affine theory,the uncertainty of distributed power output is analyzed,and a distribution network fault recovery model with the maximum loss of load recovery as the objective function and system operation reliability as the constraint is established.Secondly,according to the piecewise linear approximation idea the original quadratic constraint is converted into a linear solvable form,and at the same time,a decomposition algorithm is used to iteratively solve the converted fault recovery model.Finally,the simulation test results of a numerical example show that the proposed fault recovery method can recover more power-loss loads under severe scenarios of power fluctuations,which has high engineering application value.

Research on Key Technology of Uninterrupted Operation Load Without Power Outage in Low Voltage Transformer Area of Mobile Generator

CHEN Chao, DING Yimin, JIN Guozhong, WU Xiangyuan, BAO Weifeng, BAI Huadong

2021, 0(12):  85-89.  doi:10.16628/j.cnki.2095-8188.2021.12.015

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This paper describes the application status of 0.4 kV emergency power generator vehicle to ensure the power supply,the load outage and operational defects caused by the operation detection of distribution network are described in detail.A fast switching method of uninterrupted operation load without power outage in lowvoltage transformer area of mobile generator is proposed. It uses high response excitation driving technology of the change-over switch,and through the DSP high-speed sampling to predict the action time of grid connection conversion accurately.After the grid-connection,instantaneous detection at grid-connection time and instantaneous disassembly technology are used to ensure the load in the case of without power outage to achieve a smooth transition between the mains and generators.After the field operation test,it shows that this method is more efficient,safe and reliable for the operation and inspection of distribution network without power outage.