Hunan Electric Power

Influence and Optimization of Shielding Fitting on Voltage Distribution of Series Multi-break Mechanical Switch of Hybrid Circuit Breaker

WANG Huaqing, HUANG Daochun, SHUANG Mingjing, Li Huipeng, CHEN Xin, QIU Yiqun

2022, 42(4): 1-6. doi:10.3969/j.issn.1008-0198.2022.04.001

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In order to study the influence of shielding fitting on the voltage distribution of series multi-break mechanical switch of hybrid DC circuit breaker, and provide support for the voltage sharing design of fast series multi-break mechanical switch of hybrid HVDC circuit breaker, a typical ±200 kV hybrid DC circuit breaker model is established in this paper. The influence of the power electronic module, the energy absorption module and the shielding fitting on the voltage distribution characteristics of the break of the fast mechanical switch is analyzed by using the electrostatic field simulation, especially the influence of the structural parameters and arrangement of the shielding fitting on the voltage distribution characteristics of the break. The results show that the shielding fitting has the greatest influence on the voltage distribution between the breaks, the voltage distribution between the breaks can be effectively improved by means of the completely enclosed structure of the top layer shield, and reduce the distance between the top layer shield and the fast mechanical switching unit. Based on the simulation results, the structure parameters and arrangement mode of ±200 kV hybrid shielding DC circuit breaker fitting are optimized, the optimized voltage percentage of the high voltage side break decreases from 59.97% to 52.32% and it shows the effectiveness of the optimization measures. The results of this paper can provide a reference for the design of voltage sharing design of series multi-break mechanical switches for hybrid DC circuit breakers.

IGBT Open Circuit Fault Diagnosis Method Based on Nearest Level Approximation Modulation

RONG Fei, SUN Keqiang

2022, 42(4): 7-12. doi:10.3969/j.issn.1008-0198.2022.04.002

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This paper presents an open circuit fault diagnosis and location method for full bridge sub module IGBT based on nearest level approximation modulation (NLM) strategy and analyze.the fault characteristics of sub modules. According to the NLM modulation strategy, the sampling values of the capacitance voltage of the sub module of the bridge arm are sorted, and the median is calculated as the predicted value of the capacitance voltage of the sub module. By comparing the predicted value with the measured value, the diagnosis criterion is obtained. This method does not need to occupy too much computing resources and completes the fault diagnosis quickly. At the same time, the fault IGBT positioning and fault tolerant control of the fault sub module are realized by changing the working state of the fault sub module. Finally, a detailed simulation model is built in matlab/simulink. The simulation results verify the effectiveness of the sub module IGBT open circuit fault diagnosis and location method and fault-tolerant control strategy.

Research on Improvement Scheme of Frequency Emergency Control for New Power System

CHU Xu, XU Liqiang, YAN Yabing, LIU Qi

2022, 42(4): 13-17. doi:10.3969/j.issn.1008-0198.2022.04.003

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Due to the power characteristics of renewable energy units such as wind power and photovoltaics, and the commutation characteristics of inverter power sources such as DC transmission and photovoltaics, the new power system formed has low inertia and low damping. The system frequency changes quickly and the amplitude is large under the power grid big disturbance scenario. Therefore, it is urgent to study the frequency emergency control improvement scheme suitable for new power systems. Based on the analysis of the frequency characteristics of synchronous machines and inverters, this paper proposes a new power system frequency emergency control improvement scheme that considering distribution network activation, energy storage and renewable energy coordination. The algorithm calculates the real-time power direction of the transmission channel between the active distribution network and the main network, realizes frequency regulation according to the difference of power supply and load attributes, and realizes fast and efficient system frequency emergency control according to the regulation characteristics of energy storage and renewable energy.

Insulator Pollution Monitoring Based on Acoustic Signal and One-Dimensional Convolutional Neural Network

LI Zhenhua, LI Hao, HUANG Jingguang, ZHANG Lei, WU Lin

2022, 42(4): 18-22. doi:10.3969/j.issn.1008-0198.2022.04.004

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Aiming at the problem of discharge mode monitoring of polluted insulators in high voltage transmission lines,a new one-dimensional convolutional neural network structure (1D-CNN) is designed for monitoring the discharge patterns of fouled insulators in high-voltage lines, and a fouled insulator discharge pattern monitoring method based on acoustic emission signals and 1D-CNN is proposed. After preprocessing the acoustic emission signals collected in the laboratory under different discharge states, the convolutional neural network is used to perform adaptive feature extraction and feature dimensionality reduction on the discharge signal samples to reduce the training model parameters and computation, and finally the Softmax function is used to classify the prediction results. The recognition results show that the model can achieve a recognition rate of more than 99.84%, which effectively solves the process of manual preprocessing of data in the traditional insulator fouling degree monitoring method and can be effectively applied to the task of fouling insulator discharge pattern monitoring.

Research on Lithium Battery Parallel System and Level Difference Coordination in Substation

ZHAO Wenqin, XIAO Hui, ZHANG Maolin, LI Yihang, LONG Feiyu, WEN Zhang

2022, 42(4): 23-27. doi:10.3969/j.issn.1008-0198.2022.04.005

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The DC system is the last barrier of the substation power supply system, and its power supply reliability directly affects the operation of the entire substation. Based on a 220 kV substation, using lithium iron phosphate batteries to replace the original lead-acid batteries, this article analyzes the characteristics and applications of lithium iron phosphate batteries advantages and feasibility, studies the topological structure of the DC system, and calculates the short-circuit current of the upgraded DC system. According to the calculation results, and referring to the circuit breaker tripping curve, the paper analyzes the rationality of its level difference coordination, and points out the defects of the converter and the fuse. It provides a basis for the further upgrade and transformation of the DC system.

Design and Simulation of Equalization Circuit for Lithium-Ion Battery

ZHU Hao, LIAO Honghui, E Jiaqiang, DENG Yuanwang

2022, 42(4): 28-32. doi:10.3969/j.issn.1008-0198.2022.04.006

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In applications such as energy storage plants and pure electric vehicles, cell units are integrated in the battery pack in series and parallel,the battery packs may not be consistent with each other when in use, and this inconsistency can affect battery life and range. Aiming at this phenomenon, the paper designs the balanced topology circuit between the module and the module, analyzes the balanced principle of the designed circuit,builds the energy transfer model and the module internal balanced model in the Simulink/Simpowersystem, and simulates the equilibrium topology.The results show that the designed equalization system can realize the energy equalization of the battery.

Study on Voltage Sag Flexible Management Strategy with Energy Storage Device

ZENG Jinhui, HUANG Xi, WANG Can, LAN Zheng, LIANG Bowen

2022, 42(4): 33-39. doi:10.3969/j.issn.1008-0198.2022.04.007

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In order to reduce the influence of power grid voltage sag on the safe operation of sensitive loads, this paper proposes a flexible voltage sag management strategy with energy storage device, which can take into account voltage sag management while peak clipping and valley filling. Firstly, the DC component of power grid voltage is extracted by differentiating the dq component of power grid voltage to realize the accurate detection of power grid voltage sag amplitude and phase, and achieve the effect of improving the dynamic response speed of the system. Secondly, in the power grid voltage sag and recovery stage, the flexible switching strategy is used to realize the flexible compensation of sag voltage, so as to reduce the current impact of sensitive loads before and after voltage sag and ensure the steady-state accuracy of output voltage. Finally, a simulation model is built on MATLAB/Simulink platform to verify the correctness and effectiveness of the proposed flexible governance control strategy.

Deadbeat Control of LCL Photovoltaic Inverter Based on Compound Prediction

LI Shengqing, YAO Xin, FENG Haotian, ZHANG Dong, TANG Xinyun

2022, 42(4): 40-45. doi:10.3969/j.issn.1008-0198.2022.04.008

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Aiming at the problems of time delay and low prediction accuracy of traditional deadbeat control, a deadbeat current control based on composite prediction is proposed. This method first analyzes the reasons for the time delay and low prediction accuracy. Then, when the load is stable, Lagrange interpolation method and repeated prediction are combined to improve the current prediction accuracy. When the load changes, adaptive forward linear current prediction is introduced to shorten the system oscillation time and enhance the dynamic response ability. Finally, the two methods are combined for control. The inverter output current is predicted one beat in advance and the sampling reference current is predicted two beats in advance, which solves the problem of time delay. The simulation results show that this method reduces the harmonic content by 92% and the oscillation time by 50% compared with that before compensation. It has higher prediction accuracy and dynamic response ability, and better control effect.

Research on Cross-Section Overload Control Time of 500 kV Main Transformer after N-1 Fault

KANG Long

2022, 42(4): 46-49. doi:10.3969/j.issn.1008-0198.2022.04.009

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In order to solve the problems of cross-section power exceeding limit and power supply capacity decreasing after N-1 fault, the characteristics and reasons of cross-section exceeding control time are analyzed, and the visualization method of pre-plan is put forward. By making the accident preplan of 500 kV main transformer failure in the graphical and batch control one cliok operation of the system, fast load transfer or cut-off under 500 kV failure is realized, it provides a reference for realizing fast control cross-section limit crossing when 500 kV main transformer fails.

Research and Engineering Application of Low Pressure Cylinder Uncovering Technology for Nuclear Power Steam Turbine

LIU Jinwei, LIU Jian, LI Debo

2022, 42(4): 50-55. doi:10.3969/j.issn.1008-0198.2022.04.010

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In view of the field uncovering operation of steam turbine of a nuclear power unit, the center of low and low pair wheels and the clearance of flow through half cylinder are measured, and the data of the test process are analyzed, the test results provide reference for the following work of uncovering cylinder and equipment installation of the same type of steam turbine.

Design and Verification of Balance Performance for 550 kV High Capacity Ice-Melting Disconnector

WU Shang, TANG Xueping, WANG Chunhua, MA Weijun, WU Qigang

2022, 42(4): 56-59. doi:10.3969/j.issn.1008-0198.2022.04.011

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The ice melting disconnector of 550 kV line is installed outdoors. When the high-voltage transmission line needs ice melting treatment, the ice melting disconnector is also likely to be in icing state. Therefore, it is particularly important to meet the balance performance design under different working conditions. According to the requirements of product technical parameters, the structure of 550 kV high-capacity ice melting disconnector is designed. On this basis, the balance performance of ice melting disconnector under different working conditions is designed and checked. The results show that the balance performance of the 550 kV high-capacity ice melting disconnector meets the operation requirements under normal operation and 20mm icing conditions, and the balance performance design method adopted is generally applicable.

Application of Creep Monitoring Device of Hydropower Unit Based on Magnetic Stripe Encoder

WANG Kai

2022, 42(4): 60-63. doi:10.3969/j.issn.1008-0198.2022.04.012

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Based on the creeping phenomenon of hydraulic turbine generator set, this paper designs a set of creep monitoring device based on magnetic stripe encoder,which can sense the magnetic stripe through the encoder and send out pulse signals.After the PLC controller collects this pulse signal, it carries out PLC program processing and logic judgment.It can realize the creep signal monitoring of water turbine generator set with high cost performance, high precision and high reliability.At the same time, the protection program after unit creep is designed,to ensure the safe and stable operation of the unit.

Design and Application of Complex Terrain and Omni-Directional Modular Quick Installation Insulating Tower Platform

BAI Jianfeng, LEI Dongyun, XIAO Liyong, LI Jinliang

2022, 42(4): 64-69. doi:10.3969/j.issn.1008-0198.2022.04.013

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With the increasing demand for reliable power supply in distribution network, it is urgent to carry out uninterrupted power supply in the whole region. In order to adapt to the live working environment of power distribution under different terrain, the advantages and disadvantages of common live working insulation platforms are compared and analyzed, and an complex terrain and omni-directional modular quick installation insulation tower platform is designed in this article. A tower body, a hoop holding device, an auxiliary platform and a working platform is comprised in the device.Modular tower section is adopted, inverted or rotary installation mode is designed, and the method of fixing relying on concrete pole is designed in this design. It can meet the three main functional requirements of quick disassembly and quick assembly, multi-purpose and heavy load. The device is suitable for the live working environment of 10 kV overhead distribution line under complex and changeable terrain. The problems of difficult installation and connection of common insulation platforms in rural areas, high requirements for ground flatness, small application scenarios are solved.

Method and Its Application of Power Communication Critical Service Centralized Monitoring Based on Communication Management System

LI Hongyun, LIANG Qiong, TAN Biao

2022, 42(4): 70-74. doi:10.3969/j.issn.1008-0198.2022.04.014

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With the rapid growth of service scale, the cross-bearing phenomenon of service in all levels of electric power communication network is becoming more and more serious. Business units can not monitor the running status of important business,and it is difficult to adapt to the needs of safe operation. This paper introduces a method of centralized monitoring of important services based on communication management system and its application in Hunan third and fourth level electric power communication network.The results show that this method can effectively improve the monitoring efficiency of important business.

Optimal Scheduling of Distributed Generation System for Kitchen Waste Treatment Plant Based on Model Predictive Control

LI Anle, YI Zhigang, PENG Xing

2022, 42(4): 75-80. doi:10.3969/j.issn.1008-0198.2022.04.015

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To make full use of the distributed power generation system in the food waste treatment plant, meet the plant power demand, and reduce the power consumption of the grid while reducing the impact on the grid, the optimal dispatching strategy of the distributed power generation system based on model prediction control is proposed. Firstly, the power output of distributed power generation system is day-ahead predicted, and the load demand plan for upper grid power is calculated by combining with plant power consumption. Then, the output of energy storage system is optimally dispatched on a rolling basis based on model prediction control, and the prediction error of distributed power generation system is suppressed by reasonably adjusting the power output of energy storage system. Finally, the actual example of a waste treatment plant is verified, and its economic and environmental benefits are measured. The results show that the proposed strategy has high environmental and economic benefits.

Research on Grid Source Coordination Technology Problem in New Energy Power Station

LIU Hui, XIE Wei, LI Chengshuai, GUO Feiyang

2022, 42(4): 81-84. doi:10.3969/j.issn.1008-0198.2022.04.016

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To build a new electric power system, it is necessary to solve the impact of new energy power stations on the stability of power systems, and improve the grid-source coordination performance of new energy sources.Based on the on-site grid-related test data, the test results of power quality, active and reactive power control performance, SVG performance, fault traversal performance and grid adaptability of the new energy power station are statistically analyzed.It is pointed out that the testing project of fault traversal performance and adaptability of power grid is the weak point of the current coordination and management of network sources of new energy field stations, and it should be the key work in the future.The typical problems of fault traversal and network adaptability are summarized and analyzed, and the corresponding countermeasures are put forward from the managerial and technical levels to support the transformation and development of power system.

Robustness Evaluation of Erection Adjustment of Thrust Bearing for Hydrogenerator

WU Hongguang, HU Feng

2022, 42(4): 85-89. doi:10.3969/j.issn.1008-0198.2022.04.017

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Taking the replacement of an elastic disk-supported thrust bearing as an example, aimed at the deviation in its installation and adjustment, by constructing the coupling equations of the key parameters, such as structural stress, oil film thickness and so on, the robustness of the relevant parameters is solved.It is pointed out that the deviation of lubricant film of thrust bearing is much less than that of structural adjustment in a certain range and it is proportional to the rigidity coefficient of supporting structure. Based on the above analysis, this paper further discusses the basic principles of installation and adjustment of the elastic bearing type thrust bearing, which has reference significance for the installation and adjustment of the various bearing types thrust bearing.

Research on Reliability Improvement of Automatic Switching Logic of Station Power Supply System in Converter Station

WANG Yingkun, LIU Shunyi, HUANG Chen, LI Qianru, YANG Jiangtao

2022, 42(4): 90-94. doi:10.3969/j.issn.1008-0198.2022.04.018

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The station power supply system of ±800 kV ultra-high voltage Shaoshan converter station is taken as an example in this paper.The composition of the whole station power supply system and the automatic switching logic of 10 kV and 400V power supply are introduced. In view of the problems existing in the automatic switching logic of 10 kV and 400 V power supply, scientific and reasonable suggestions are introduced to improve the reliability of the DC transmission system.

Research on Automatic Inspection Technology of Relay Protection in Power System

CHEN Yuzhi, XU Hao, DONG Yali, SUN Xiaojia, LI Peng, CHEN Zhibiao, BIAN Husai

2022, 42(4): 95-98. doi:10.3969/j.issn.1008-0198.2022.04.019

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Due to the large area, the distributed and remote substations in Tibet, and the low efficiency in detecting and treating hidden troubles in the secondary system, the relay protection function can not be fully developed. In order to meet the demand of power supply safety in this area, based on the existing fault information processing system, the logic rules and advanced functions are developed, the system software products are developed, and the second professional patrol inspection is upgraded from manual to automatic mode,to ensure the real-time and lean quality of the second round inspection.

Reactive Power Optimization Control Strategy of Wind Farm in Electricity Market

LIU Yi, ZHU Jiran, DENG Wei, ZHANG Di, REN Lei, LUO Guanru

2022, 42(4): 99-105. doi:10.3969/j.issn.1008-0198.2022.03.020

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In the power market, setting an appropriate price for reactive power is conducive to mobilize the enthusiasm of power producers to participate in system voltage regulation. Firstly, this paper proposes a reactive power pricing method under the environment of power market. This method combines the P-Q curve of the generator itself and considers the Loss cost and opportunity cost when the generator emits reactive power to set the price for reactive power. Then, for the wind farm composed of permanent magnet direct drive wind turbines, a reactive power optimization strategy with the objective function of minimizing the active power network loss, load node voltage deviation and reactive power purchase cost in the system is proposed. This strategy can effectively reduce the system operation cost, improve the system voltage stability, and ensure the economic interests of both power producers and power grid. Finally, taking IEEE-14 bus system as an example, the corresponding simulation model is established in GAMS simulation software, and the mixed integer nonlinear programming (MINLP) solver in the software is used to solve the proposed optimization problem. The simulation results verify the rationality and effectiveness of the optimization model proposed in this paper.

Application Research of Hydraulic Cavitation Technology for Oily Wastewater in Accident Oil Pool

QIU Binbin, LI Guoyong, ZHANG Huadong, WANG Xiaohao

2022, 42(4): 106-109. doi:10.3969/j.issn.1008-0198.2022.03.021

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At present, in the field of oil-water separation and deep purification of oily wastewater in substation, there is no mature technology that can meet the standard discharge of oily wastewater with different concentrations and give consideration to high efficiency and economy. This paper proposes an oily wastewater treatment technology using hydraulic cavitation oil-water separation method coupled with ozone chemical technology. In the early stage, after removing most of the oil slick with hydrocyclone, the emulsified oil that is difficult to remove enters the hydraulic cavitation unit, and a small amount of floating oil and emulsified oil are oxidized into small molecular substances through the cavitation effect to be removed. At the same time, the ozone generated by the ozone generator can strengthen the oxidation reaction efficiency, improve the equipment treatment capacity and reduce the content of oil and organic matter in the subsequent effluent. By setting up an experimental platform and configuring oily wastewater with different oil content for test, the total oil content of oily wastewater can be significantly reduced to 5mg / L, which verifies the feasibility and efficiency of this technology.

Analysis of Loop Network Fault Harm in DC Power System

CAO Wenbin, LUO Wei, CHEN Ruizhen

2022, 42(4): 110-114. doi:10.3969/j.issn.1008-0198.2022.03.022

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DC loop network fault is one of the common forms of insulation faults in DC power systems. This article analyzes the causes, types and hazards of ring network faults. Focusing on the equivalent circuit of the DC power system, the voltage manifestations of various ring network faults are expounded from the perspective of circuit structure, and the essence of loop network fault hazards is revealed. Finally, according to the physical phenomenon of the loop network fault, the specific operation method of the loop network fault is given.

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