Table of Content

25 February 2022, Volume 42 Issue 1

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Application of Matlab GUI in Ferroresonance Simulation

GAN Wangwei, PU Xi, TAO Jingsong, ZUO Jian, CHEN Daojun, LIU Yongyan

2022, 42(1):  1-7.  doi:10.3969/j.issn.1008-0198.2022.01.001

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In 10 kV low-voltage distribution network, the ferroresonance phenomenon caused by the saturation of electromagnetic voltage transformer core will seriously affect the safe and stable operation of power system. In this paper, a 10 kV neutral ungrounded distribution network system is taken as the research object, and the simulation model of ferroresonance is established by using Matlab/Simulink. Taking the disappearance of single-phase short-circuit to ground fault as the resonance trigger condition, the influence of system to ground capacitance on resonance type is studied. In order to optimize the shortcomings of Simulink simulation, such as the need to open the model parameter editing interface one by one when modifying the control parameters, this paper creatively introduces the Matlab graphical user interface (GUI) to present the parameter adjustment, model operation and result display in a unified interface, which improves the user experience to a certain extent.

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Magnetic Circuit Analysis and Loss Checking Test of Transformer Low Voltage Lead Wire

LIU Zhuochang, HUANG Dengwei, LI Weifeng

2022, 42(1):  8-12.  doi:10.3969/j.issn.1008-0198.2022.01.002

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At present, large-capacity distribution transformers and new energy transformers are widely used, the low-voltage lead wire used in this transformer need to occupy a larger fuel tank space. A new type of low voltage lead wire structure can effectively reduce the size of fuel tank and has been applied in pilot. After studying the magnetic circuit of the clamp with the new lead structure, it is found that although the overall magnetic motive force of the clamp is zero, there are local magnetic flux changes of the clamp. The results show that the local magnetic induction intensity of the low voltage clamp is higher and the loss of the clamp is increased obviously. It shows that the new lead wire structure has defects and local overheating risk. The load loss of the actual case is measured to verify the accuracy of the simulation results.

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Reactive Power Control Strategy of DFIG Grid-Connected Wind Farm Based on STATCOM/BESS

KUANG Wei, KUANG Honghai, YU Xiqi, SU Fuqing, TAO Cheng

2022, 42(1):  13-16.  doi:10.3969/j.issn.1008-0198.2022.01.003

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Aiming at the system stability problems existing in large-scale grid connection of new energy, this paper analyzes the reactive power compensation capacity of DFIG units, introduces battery energy storage static synchronous compensator (STATCOM / BESS) into DFIG grid connection system, and puts forward a method to maintain the power and voltage stability of DFIG wind power grid connection system by using STATCOM / BESS. Based on the traditional STATCOM reactive power compensation, the battery energy storage is connected in parallel on its DC side, which can quickly and smoothly adjust the active power of the wind farm input and network point, support the system voltage stability, and achieve the function of peak shaving and valley leveling. By comparing the reactive power compensation capability of DFIG, STATCOM and STATCOM / Bess in case of three-phase grounding fault, the results show that the system with STATCOM / Bess has the smallest voltage drop, the fastest recovery speed and the best compensation effect.

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Research on Ferroresonance and Lightning Overvoltage Identification Method Based on Multi-Level Support Vector Machine

ZHAO Hongbin, LUO Qingliang, LI Xin, XIANG Yingzhu, HE Zhiqiang, DENG Hualong

2022, 42(1):  17-22.  doi:10.3969/j.issn.1008-0198.2022.01.004

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Aiming at the frequent occurrence of overvoltage in power system, which seriously threatens the safety of equipment and personnel, a pattern recognition method based on support vector machine is proposed. Based on the overvoltage waveforms collected by Chongqing 110 kV substation, the characteristic differences of different overvoltage waveforms are analyzed, and then six kinds of characteristic quantities that can effectively reflect the difference between ferroresonance and lightning overvoltage are extracted by time domain analysis and frequency domain analysis. Finally, the extracted characteristic quantities are applied to overvoltage pattern recognition. The theoretical basis of support vector machine used in this recognition method is simple and intuitive. The simulation results show that this method can correctly identify ferroresonance and lightning overvoltage, and has the advantage of fast recognition speed.

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Research on Maximum Penetration Level of Wind Power Considering Wind Speed Fluctuation and Frequency Constraint

LU Dingwen, LIAO Kai, SHEN Yangwu, WANG Min

2022, 42(1):  23-31.  doi:10.3969/j.issn.1008-0198.2022.01.005

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With the continuous improvement of global wind power penetration level, the inertia level of power system continues to decline, and due to the influence of wind speed fluctuation, the fluctuation of system frequency is further increased, which restricts the maximum penetration level of wind generation. Therefore, aiming at the influence of wind speed fluctuation on system frequency, a low-order system frequency response model considering wind speed fluctuation is established, and a wind turbine primary frequency regulation control method based on virtual filter is proposed. By adding an additional control loop to the load shedding power controller, on the basis of not affecting the original primary frequency regulation ability of the wind turbine, the influence of wind speed fluctuation on system frequency is suppressed, and the maximum penetration level of wind generation is improved. In addition, in order to measure the improvement effect, a calculation method of maximum penetration level of wind generation considering wind speed fluctuation and frequency constraints is proposed. Finally, the IEEE9 node time domain model with wind turbines is built on Matlab/Simulink, and different simulation scenarios are set to verify the accuracy of the proposed calculation method and the effectiveness of the proposed control method.

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Research on Identification Method of Voltage Sag Cause Based on BiLSTM

SU Tingting, PENG Hexiang, WANG Can, LI Bo, LIAO Kai, LIU Shifeng

2022, 42(1):  32-37.  doi:10.3969/j.issn.1008-0198.2022.01.006

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Voltage sag is one of the most common power quality problems in distribution network. Accurately identifying the causes of voltage sag is of great significance to formulate comprehensive prevention and control scheme of voltage sag and division of power grid user responsibility. A method for identifying the cause of voltage sag based on bidirectional long-term and short-term memory(BiLSTM)neural network is proposed. Firstly, the time-domain characteristics of voltage sag and S-transform energy entropy are extracted, and the comprehensive characteristic index of voltage sag cause identification is constructed.Secondly, a BiLSTM network suitable for voltage sag classification is established to identify the causes of voltage sag.Finally, the evaluation index of multi classification problem is set, and the effectiveness of the proposed identification method is verified by simulation. Simulation results show that the proposed method can identify five voltage sag disturbance sources with high accuracy.

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Design of Low Current Standard Power Source for High-Precision Gateway Watt-Hour Meter Verification

YANG Jing, ZENG Weijie, WANG Zhi, SHEN Liman, SU Yuping

2022, 42(1):  38-42.  doi:10.3969/j.issn.1008-0198.2022.01.007

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In order to solve the problem that the accuracy of 0.3 A low current output is low in the verification of high precision gateway watt-hour meter, a low current output scheme based on trans-resistance negative feedback is proposed, and the feedback measurement module and noise filtering unit are designed, a low current standard power source is developed. The experimental results show that the designed small current standard power source is stable and reliable, and the problem of verification and tracing of small current points in 0.3 A and above gateway meter is solved.

New technology and Application

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Multi-End Traveling Wave Fault Location Algorithm for Distribution Network Based on Path Search

YOU Jinliang, ZHANG Di, KANG Tong, ZHU Zheming

2022, 42(1):  43-47.  doi:10.3969/j.issn.1008-0198.2022.01.008

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The distribution network has complex structure, and mostly tree-shaped radial distribution.Many branches on the feeder and the network topology often changes. The traditional fault location method is difficult to apply to the accurate fault location of the distribution network. In this paper, a multi-end traveling wave fault location algorithm based on path search is proposed. Firstly, a new distribution network association matrix is constructed, which fully expresses the topology of the distribution network. Then the path search method is put forward. The shortest path between the end nodes and the route that passes through are arranged. Finally, the multi-terminal transient traveling wave information is comprehensively utilized to achieve accurate positioning of the distribution network. The simulation results show that the algorithm can quickly and accurately give the fault distance and the path search can realize the initial traveling wave propagation process in the distribution network.

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Research on UAV Inspection System for Substation Oil Level Meter Equipment

ZHANG Haihua, CHEN Hao, LI Zhongxuan, LIU Huaiyu, SUN Xiaolei, XU Chi

2022, 42(1):  48-52.  doi:10.3969/j.issn.1008-0198.2022.01.009

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With the continuous in-depth application of unmaned aerial vehicle(UAV) in substation inspection work, reading of oil level/meter equipment such as current transformers (CT), transformers, and circuit breakers has become an urgent need. The current UAV inspections with manual flight operations, or with isolated network by manually exporting inspection image, have not been integrated with the intelligent inspection system of the running private network in the substation. Taking the construction of the UAV inspection system in the substation as the starting point, this article decomposes the components of the UAV inspection system in the substation and analyzes the various functional modules. Based on the communication protocol and network topology of UAV, airports, and third-party platforms, two private network access methods of wired network and wireless network are discussed. The actual application of the substation site verifies the feasibility and effectiveness of the scheme, and realizes the autonomous inspection of the 500 kV CT oil level by the UAV. The inspection accuracy and inspection efficiency are better than those based on high-definition video inspection technology.

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Summary of Anti-Freezing and Melting of Wind Power Transmission Lines in Hunan Power Grid

LI Bo, HU Jinli, MAO Xinguo, ZHU Siguo, ZHANG Jingfan

2022, 42(1):  53-55.  doi:10.3969/j.issn.1008-0198.2022.01.010

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With regard to current situation and existing problems of wind power transmission line in Hunan, this paper provides guidance for freezing prevention and deicing on both technology and management, introduces engineering applications, and guide scientifically the overall level of anti-freezing and melting of wind power transmission lines in Hunan power grid. It is of great significance to guide the overall level of anti-freezing and melting of wind power transmission lines in Hunan power grid in order to promote the implementation of “double carbon”and “building a new power system with new energy as the main body”in Hunan.

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Research on On-Site Verification Techology of Electric Energy Measurement of DC Charger

WANG Zhi, WANG Haiyuan, ZENG Weijie

2022, 42(1):  56-59.  doi:10.3969/j.issn.1008-0198.2022.01.011

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At present, there is no effective traceability system for the value of DC electric energy. DC electric energy cannot be measured and traced to the national standard, which is not convenient for accurate billing and settlement. This paper studies the on-site calibration technology of DC charger electric energy measurement, analyzes the error of DC electric energy measurement, and proposes a scientific and feasible DC energy measurement traceability scheme, which provides important support for ensuring the accuracy of DC measurement. The experimental results show that the on-site verification and error analysis method of DC charging electric energy measurement proposed in this paper is feasible and effective.

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Methods of Improving Cloud-Based Comprehensive Intelligent Warning Accuracy in Hunan Power Grid

GONG Yusheng, HONG Quan, LI Zhenwen, WU Jinbo, ZHANG Ruochen

2022, 42(1):  60-63.  doi:10.3969/j.issn.1008-0198.2022.01.012

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In order to further improve the accuracy of the control cloud platform trip information alarm,and improve the basic data quality of the platform, this article proposes related issues and solutions that affect the accuracy of program research and judgment during the operation of the cloud platform.

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Short-Term Load Forecasting Method Based on QPSO-ELM Combined with GA Theory

CHEN Yonglong, SHI Qi, WANG Erqing

2022, 42(1):  64-70.  doi:10.3969/j.issn.1008-0198.2022.01.013

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In order to screen out the nonlinear relationship in massive load data more quickly and improve the accuracy of short-term load forecasting model, this paper focuses on the shortcomings of quantum particle swarm optimization algorithm (QPSO) in dealing with complex high-dimensional parameter optimization problems, and the genetic quantum particle swarm optimization algorithm (GAQPSO) combined with hybrid evolutionary theory of genetic algorithm (GA) is proposed to optimize the input weight and hidden layer deviation of the regular extreme learning machine, which forms a hybrid short-term load forecasting GAQPSO-ELM model. Meanwhile, when the input features are selected, the influences of historical load, temperature, time interval and type of date are fully considered, so the accuracy of the short-term load forecasting model is further improved. The experimental result shows that the proposed short-term load forecasting model has a higher accuracy than the QPSO-ELM model and the common ELM model, and it can better reflect the change trend of the daily load curve, which verifies the effectiveness of the proposed predictive model.

Experience and Discussion

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Prediction of Boiler Reheat Steam Temperature Based on Multi-Layer Perceptron Neural Network

CHEN Gang, PU Jingfan, MEI Hailong, YU Bing, ZHANG Lin, SHI Chuan, TAN Peng

2022, 42(1):  71-75.  doi:10.3969/j.issn.1008-0198.2022.01.014

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In order to absorb large-scale new energy into the power network, coal-fired power stations require frequent load adjustments, which brings some difficulties to reheat steam temperature control. Based on the historical operation data of a certain 1 000 MW ultra-supercritical coal-fired boiler, a prediction model of boiler reheat steam temperature based on multi-layer perceptron (MLP) neural network is established. The results show that the mean square error of the reheat steam temperature prediction model is only 0.71℃, which is superior to long and short term(LSTM)neural network and short vector machine (SVM)in mean relative error, correlation coefficient, training time and generalization effect. Introducing the prediction results of the model into the controller is helpful to improve the reheat steam temperature control quality.

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Research on Stability Coordination Strategy of Park Wind-Photovoltaic Storage System Considering Reactive Power Compensation

PENG Zheng, LIN Jinjie

2022, 42(1):  76-83.  doi:10.3969/j.issn.1008-0198.2022.01.015

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There are some problems such as power grid structure reconstruction and power flow distribution characteristics when the wind-photovoltaic power generation system is integrated into the park′s public power grid. Considering the energy storage system “peak load and frequency regulation” feature, from the perspective of energy coordinated control, the paper proposes an energy storage device to regulate the park scenery storage integration of core system reactive power optimization control strategy, and the neural network particle swarm optimization (PSO) algorithm is used to solve the energy storage capacity optimization of the output of different control objectives. Compared with the traditional coordinated control mode, the flexible interconnection between low-voltage power grid feeders in the park and the stability of power flow switching of distributed energy supply are greatly improved under the appropriate iterative optimization of energy storage capacity. The integrated model of landscape storage in MATLAB/Simulink verifies the effectiveness and correctness of the proposed control strategy.

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Performance Test of Low Current Grounding Line Selection Device Based on Real-Time Digital Simulation System

XU Biao, ZANG Xin, OUYANG Fan, LI Hui, LIANG Wenwu

2022, 42(1):  84-88.  doi:10.3969/j.issn.1008-0198.2022.01.016

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Single phase grounding fault is the most common fault type in small current grounding distribution network, but the on-site low current grounding line selection device is often difficult to meet the application requirements, affecting the rapid and accurate treatment of grounding fault. Considering that there are many low current grounding line selection manufacturers and various device forms, it is difficult to intuitively evaluate the line selection performance of different devices and make horizontal comparison, and there is no supporting basis for the selection and application of on-site line selection devices. Therefore, based on the real-time digital simulation system(RTDS), this paper establishes a test platform for small-current grounding line selection device, and carries out parallel testing of different line selection devices. Through the same test under all-round fault scenarios, it provides strong support for the pilot application of small current line selection device.

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Research on New Power Coordinated Control Strategy for Doubly Fed Wind Turbine

WANG Xiaojun, DUAN Shengqiang, CHEN Wenkui, Ayisulu ENIWAL, ZHAO Yanrong, CHEN Xu

2022, 42(1):  89-93.  doi:10.3969/j.issn.1008-0198.2022.01.017

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Aiming at the problem of voltage fluctuation at the parallel point caused by the gradual increase of wind power grid scale, this paper proposes a new power coordination control strategy considering the reactive power regulation ability of doubly-fed wind turbine (DFIG) itself, that is, according to the response time difference between DFIG and static synchronous compensator(STATCOM).The complementary empirical mode decomposition algorithm (CEEMD) is used to divide and reconstruct the reactive power regulation required by wind farm merging nodes into two frequency bands, which are used as the reference power of DFIG and STATCOM respectively to coordinate the two bands to suppress the voltage fluctuation of the merging nodes. Based on this, the Matalb simulation model is established to verify the effectiveness of the proposed strategy.

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Research on Impact of Distributed Photovoltaic on Distribution Network Based on RTDS Modeling

LONG Xuemei, YAN Yabing, DING Yu, OUYANG Zongshuai, HE Silin

2022, 42(1):  94-99.  doi:10.3969/j.issn.1008-0198.2022.01.018

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With the large-scale promotion of distributed photovoltaic, it is necessary to study the impact of distributed photovoltaic access to distribution network on voltage, current and relay protection. Firstly, according to the typical structure of distributed photovoltaic and distribution network, the simulation model of distributed photovoltaic access to distribution network is established based on RTDS. Secondly, the influence of distributed photovoltaic on distribution network voltage and current under different photovoltaic permeability, fault type and fault location is simulated and analyzed. Then, the influence of distributed photovoltaic on distribution network relay protection under power grid fault state is studied. The simulation results show that after the distributed photovoltaic is connected to the distribution network, the voltage increases and the current provided by the system decreases. When the distributed photovoltaic permeability is large, the overcurrent protection may refuse to operate and the reclosing may fail. Therefore, the protection setting needs to be reset.

Faults and Analysis

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Analysis of a Over-Voltage Fault in DC Ice-Melting Device

MO Yanjun, SU Wenyan, HUANG Runqing, WU Zhen, ZHU Yuan

2022, 42(1):  100-102.  doi:10.3969/j.issn.1008-0198.2022.01.019

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This paper analyzes the a typical over-voltage fault caused by the misoperation of DC ice-melting device. It is pointed out that the direct cause of this failure is that the AC voltage output from the DC melting device reacts to the device itself and due to the protection of the surge arrester, the ice melting device can still be used normally. According to the cause of the fault, some suggestions are put forward to improve the design of the current DC melting device.

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Analysis and Treatment on a Heating Fault of 110 kV Transformer Bushing

ZHUANG Xiantao, HAO Wei, CHONG Junlong

2022, 42(1):  103-106.  doi:10.3969/j.issn.1008-0198.2022.01.020

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In this paper, a heating fault of 110 kV transformer bushing is found through infrared temperature measurement. The process of fault inspection and treatment is introduced, and the reason of the heating fault is analyzed. The analysis result shows that the missing of inclined coil spring is the direct cause of this fault, and transformer operates normally after rectification. Finally, suggestions are put forward for analysis and treatment of such faults.