Hunan Electric Power

Study on Fire Extinguishing and Anti-Reburning Technology of Lithium-Ion Battery Energy Storage System

LU Jiazheng, ZHOU Tiannian, WU Chuanping

2022, 42(6): 3-6. doi:10.3969/j.issn.1008-0198.2022.06.001

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The lithium-ion battery energy storage system (ESS) has the risk of thermal runaway, fire and explosion. In this paper, aiming at the problem that lithium battery ESS is difficult to extinguish and easy to reburn, the rapid fire-extinguishing based-fluorine and passivation and anti-reburning methods are proposed. The large-scale fire extinguishing test is carried out. The results showed that the initial fire can be quickly extinguished, and the reburning doesn't occur. This research can provide a guidance for the application of fire extinguishing technology in the lithium battery ESS and future key research directions.

Fault Diagnosis Study of Oil-Immersed Transformers of Optimized Kernel Based Extreme Learning Machine Based on Modified Aquila Optimizer

YI Lingzhi, LONG Jiao, WANG Yahui, HUANG Jianxiong, SUN Tao, YU Huang, YU Guo

2022, 42(6): 7-14. doi:10.3969/j.issn.1008-0198.2022.06.002

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In order to improve the accuracy and reliability of oil-immersed power transformer fault diagnosis, an oil-immersed power transformer fault diagnosis method of optimized kernel based extreme learning machine (KELM)based on the modified aquila optimizer (MAO)is proposed in this paper. The original aquila optimizer (AO) is improved by using Tent chaotic mapping and cardinality probability density function, and the improved algorithm effectively improves the convergence speed and the accuracy of the optimization search.The optimal fault diagnosis model is constructed by jointly seeking the regularization coefficients and kernel function parameters in the KELM using the MAO algorithm. The experimental results show that the accuracy of MAO-KELM for transformer fault diagnosis reaches 95.8%, which is 3.52%, 10.07% and 11.64% higher than the optimized KELM fault diagnosis models of AO, GWO and PSO respectively, reflecting the superiority of the MAO algorithm,and comparing with the traditional model, the proposed method has obvious advantages in its diagnosis effect.

Research on New Residual Current Protector Based on Sliding Half Wave Root Mean Square Value Method

WU Chuanping, ZHU Hongzhang, XIE Yao

2022, 42(6): 15-18. doi:10.3969/j.issn.1008-0198.2022.06.003

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Due to the existing residual current protection devices using the amplitude of the fundamental residual current as the action criterion are easily to cause the protection devices failure to operate or misoperate, this paper proposes a method based on sliding half-wave root mean square value (RMS) to protect living body from electric shock. Based on the characteristic of animal living body electric shock current, calculate the half-wave RMS variety situation in the sliding window of 1.5 fundamental wave cycle time to distinguish whether living body electric shock occur. According to the proposed algorithm, a new residual current protector prototype is designed. The experimental results show that this method can accurately and quickly identify the electric shock of living body and non living body, and achieve accurate electric shock protection. It is of great significance to ensure the safety of electricity use and the reliability of power supply.

Review on Joint Emergency Operation of Mobile Energy Storage Networks and Distribution Systems

GUAN Zhanglei, ZHAO Tianyang, CAI Zelin

2022, 42(6): 19-26. doi:10.3969/j.issn.1008-0198.2022.06.004

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The increasing occurrence of extreme weather events (EWEs) are threatening the end energy consumption under high levels of electrification,and it is urgent to increase the resilience of distribution systems. To depict the status quo of joint emergence response capabilities of the mobile energy storage networks (MESNs) and distribution systems, the unconventional emergencies introduced by EWEs are treated as the start point. The prevalent modelling techniques of EWEs and their impacts on coupled electricity and power systems (CEPSs) are summarized. The emergency response capacity of MESNs is concluded from the inventory management and logistics management perspectives considering the varying reachability conditions. Based on the classical resilient management models of distribution systems, the MESNs are incorporated into the resilience enhancement schemes. The benefits allocation among MESNs and distribution systems are overviewed from game theoretical problem formulation and equilibrium computation perspectives. The further research problems on joint emergency management of MESNs and distribution systems are highlighted.

Effect of Acetic Acid on Corrosion Behavior of 2Cr12MoV Steel in Early Condensates

ZHOU Baiqing, WEI Jiaqiang, WEN Yizhang, WAN Tao, LIU Kai, GONG Shangkun, ZHA Fanglin

2022, 42(6): 27-31. doi:10.3969/j.issn.1008-0198.2022.06.005

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Aiming at the corrosion problem in the phase change zone of low pressure cylinder of steam turbine, the effect of acetic acid (HAC) on the corrosion of 2Cr12MoV steel in primary setting water is studied by means of weight loss,SEM surface topography analysis, raman spectroscopy analysis and potentiodynamic polarization test, to reveal the effect of acetic acid on the corrosion of low pressure cylinder of steam turbine. The experimental results show that the corrosion mechanism of 2Cr12MoV steel in HAC solution is a buffering mechanism, acetic acid does not directly participate in the cathodic reduction reaction, but continuously provides H⁺ to accelerate cathodic reaction by ionization.The corrosion rate of 2Cr12MoV steel increases with the increase of acetic acid concentration,the corrosion rate of 2Cr12MoV steel in 100 mg/L HAC solution decreases rapidly at the beginning of soaking and it was stable at about 0.012 mm/a after 120 h.

Research Progress and Prospect of UAV Inspection of Substation Equipment

LI Huipeng, HUANG Daochun, DENG Yongqing, LI You, ZENG Zhaoqiang, RUAN Jiangjun

2022, 42(6): 32-39. doi:10.3969/j.issn.1008-0198.2022.06.006

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The use of UAV inspection of substation equipment can achieve multi-angle, refined and high-efficiency inspection of substation equipment. However, UAV inspection of substation equipment is still at the period of research and pilot application. Research perspectives are presented based on a review of the current state of relevant research. Before large-scale promotion, it is recommended to develop technical specifications and standards for UAV inspection of substation equipment and combineing the advantages of different trajectory planning algorithms to realize the intelligent planning of global static trajectory and local dynamic trajectory. In addition, a sample library of substation equipment defects is build and algorithms such as artificial neural networks is used to promote intelligent diagnosis of hidden defects. In view of the deficiencies in the existing safety distance study, it is recommended to fully consider the special characteristics of the substation environment, and propose a safety distance determination method for UAV operations in substations. The safety distance tests of UAV measurement and control performance under electric field and magnetic field environment are carried out and the safety distance criterion is proposed. In addition, the fast analysis method of safety distance of UAV near heterogeneous electrode/conductor is established by using machine learning and data fitting.

Transformer Core Vibration Damping Technology and Three Types of Damping Rubber Performance Testing

WU Xiaowen, ZHAO Ruidun, LI Shengli, CHEN Wei, HU Sheng

2022, 42(6): 40-45. doi:10.3969/j.issn.1008-0198.2022.06.007

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A physical model of 10 kV oil-immersed distribution transformer is established to study the vibration mechanism, transmission law and damping effect of transformer core and oil tank, the vibration displacement data of transformer oil tank surface at different time with and without iron core damping gasket are analyzed. It is proved that the vibration amplitude and noise emission of oil tank can be reduced by adding damping device between oil tank and iron core to increase the loss of vibration energy in the process of transmission. According to the characteristics and application requirements of transformer oil, cork rubber, nitrile rubber and fluorine rubber were selected to test their oil resistance. The test results of damping performance show that cork rubber and NBR can not satisfy the noise suppression condition of transformer, and will increase the noise to some extent under the condition of load, the fluorine rubber damping pad can meet the requirements of vibration and noise suppression of transformer, and can effectively reduce the noise. It can be used as a potential damping pad material for oil-immersed transformer iron core.

Optimization of Passive Damping Parameters of SWISS Rectifier Based on LCL Filter Genetic Algorithm

ZHANG Yang, DENG Jiangwei, CHENG Zhun

2022, 42(6): 46-53. doi:10.3969/j.issn.1008-0198.2022.06.008

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The improved SWISS rectifier has the advantage of eliminating the commutation dead time without introducing active devices. However, the introduction of LCL filter has the problems of difficult parameter selection and current distortion caused by resonance. In this paper, for improving the SWISS rectifier, the relationship between the network-side current distortion and oscillation problems and the damping coefficient of LCL filter is analyzed, the LCL filter transfer function is constructed, the Bode diagram with different damping is compared, and a genetic algorithm passive damping parameter optimization method with minimized inductance ratio, maximized harmonic attenuation and minimized power loss of the objective function is proposed. The simulation results show that the improved SWISS rectifier front-stage LCL filter network side current harmonic content is significantly lower than the traditional trial-and-error method, the overall dynamic performance of the system is better, moreover, the parameters obtained from the global optimization of genetic algorithm have good convergence,and to some extent, the problem of choosing LCL filter parameters is solved because of the tedious steps.

Harmonic Mixed Damping Control Strategy for LLCL Grid-Connected Inverter in Weak Power Grid

LI Shengqing, TANG Xinyun, ZHU Hui, PENG Xiaowei, HUANG Xinyan

2022, 42(6): 54-58. doi:10.3969/j.issn.1008-0198.2022.06.009

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In order to suppress the harmonics of switching frequency and system resonant peak in weak power grid, a harmonic mixed damping control strategy for LLCL grid-connected inverter in weak power grid is proposed.First the LLCL type and LCL type amplitude frequency characteristics of the filter are analyzed, and then based on the active damping method to add the passive damping method, through the active damping of k value and R value set in the passive damping, under the condition of no more loss, the effect of active damping method by control delay is reduced, combining the advantages of two methods.Finally, the simulation results show that the proposed control strategy has good harmonic suppression effect, and the total harmonic distortion rate is reduced by 1.18% compared with the active damping method, and it has good stability and adaptability under different weak power networks.

Analysis and Practical Method Research Based on Industrial Level Source-Charge Three-Phase Voltage Unbalance

WANG Dan, LI Yong, HU Sijia, WU Jinbo, GONG Yusheng, PENG Yanjian

2022, 42(6): 59-63. doi:10.3969/j.issn.1008-0198.2022.06.010

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Taking the mobile load as an example, combined with the electric power acquisition parameters of the actual equipment, this paper analyzes the three-phase voltage unbalance problem of the equipment during the traction process of the power supply, and puts forward a method for eliminating the charge-source reverse order, it can guide the analysis and emergency treatment of power quality problems such as three-phase voltage unbalance of industrial-grade source load, and ensure the stability mobile industrial-grade load.

Uninterruptible Installation Method of High Voltage Circuit Breaker Online Monitoring Equipment

CHEN Hao, TAN Fenglei, XU Peng, ZHANG Haihua, HE Jiahong

2022, 42(6): 64-68. doi:10.3969/j.issn.1008-0198.2022.06.011

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Considering lack of evaluation criteria for image recognition algorithm of device defects in substation,a novel uninterruptible installation method for HV breaker online monitoring equipment is proposed in this paper and the installation without interruption of power supply is achieved. The installation in the 500 kV substation in Jiangsu province verifies the efficiency and feasibility of this installation method.

Research on Collaborative Planning Method for Incremental Distribution Network

YANG Chuyuan, YAO Junwei, Xiang Chuan, XIE Qiongyao, CHEN Zhaole, WANG Hailiang, TAN Liuye, LI Xizhe, YANG Nan

2022, 42(6): 69-75. doi:10.3969/j.issn.1008-0198.2022.06.012

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The source, network and load structure in power system has undergone profound changes, and the characteristics of source, network and load subject diversity are becoming more and more prominent. The traditional distribution network planning method has been difficult to adapt to the incremental distribution network. Under the background, this paper takes the maximum benefit of distributed power supply and distribution network company as the goal, and establishes the planning model of multi-agent game of distribution network and solves it. By combining dynamic game with static game, virtual“nature”variables are introduced and the algorithm is solved by iterative method. And the distribution network system of IEEE 33 node is used as an example to verify the simulation analysis.

Research on Thermal Power Multi-Market Joint Operation Strategy

WANG Shuqiang, LIU Shijian, HUANG Chao, LIANG Jiahao

2022, 42(6): 76-82. doi:10.3969/j.issn.1008-0198.2022.06.013

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In order to ensure the market competitiveness of thermal power manufacturers in the new power system in multiple markets, the market competitiveness of thermal power manufacturers based on the development of electricity market and auxiliary service market is analyzed. Considering the market benefit of the optimized thermal power manufacturer, the optimization model of thermal power unit output curve considering the electricity energy market and auxiliary service market is constructed. Combined with the game of multiple thermal power manufacturers connected to the grid and the basic situation of time-segment power quantity value, the output optimization model of thermal power unit based on A2C is constructed. Combined with a simulation example, the model proposed is verified to improve the market benefit of thermal power plant, and the results show that the model is economic and effective.

Equivalent Modeling of AC/DC Microgrid Connection Based on Improved Extreme Learning Machine

XI Mengrui, CAI Changchun, WANG Bin

2022, 42(6): 83-89. doi:10.3969/j.issn.1008-0198.2022.06.014

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With the increasing number of microgrid connected to distribution network, it brings challenges to the stable operation of distribution network. The equivalent modeling of microgrid is the basis for analyzing the impact of microgrid access and dynamic simulation of distribution network. Based on the theory of non-mechanistic modeling, this paper establishes an AC/DC microgrid grid-connected equivalent model of extreme learning machine with real and imaginary parts of voltage and current as input and power as output. The sparrow search algorithm is used to optimize the input weight and threshold of extreme learning machine to reduce the model accuracy problem caused by the lack of unity of input weight and threshold. Finally, the AC/DC hybrid microgrid model is built on DIgSILENT platform for verification. The simulation results show the effectiveness and accuracy of the proposed equivalent model.

Research on Power-Tapping Method from Ground Wire for Online Monitoring Equivalent of Substation Incoming Section

ZHAO Shihua, XIE Yanbin, HUANG Zimin, BI Maoqiang

2022, 42(6): 90-93. doi:10.3969/j.issn.1008-0198.2022.06.015

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Online monitoring of substation incoming section can monitor the running state of transmission line. Aiming at online powering for the monitoring device of the incoming section, the method of energy-drawing from ground-wire, power, effects of concerned factors, and overvoltage of the device are analyzed with EMTP-ATP program. The results show that the power level of the energy-drawing from ground wire is rather small, but usually enough to meet the requirements of the online monitoring devices for power. On this basis, combining the power level, lightning strike overvoltage and engineering feasibility of the energy-drawing approaches, the basic principle for selecting the approach is determined. The research results could provides reference for the on-spot powering for online monitoring device of incoming section of the substation.

Effect of CFRP/ Steel Lap Type on Performance of Lap Joint

GAO Youwei, LI Chuanxi, SITU Yinghu

2022, 42(6): 94-98. doi:10.3969/j.issn.1008-0198.2022.06.016

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In order to understand the influence of fiber laying direction on the properties of steel structures strengthened by CFRP, steel/steel, 0°/steel, 90°/steel, 90°/0°, 90°/90° and 0°/0° joint specimens were made, and there were 5 joint specimens of each type. Tensile shear test was carried out after 7 days of curing at room temperature and constant humidity. The failure mode, ultimate bearing capacity and load displacement curve of the specimen were investigated to explore the effect of the joint type on the performance of CFRP/ steel lap joint. The results show that the failure mode of the specimens containing 90° fibers is CFRP/ steel interface failure. The failure mode of 0°/steel specimen is CFRP/ rigid interface failure. The failure mode of 0°/0° specimens is CFRP interlayer failure. For the specimens containing 90° fiber, the shape of load-displacement curves of the same group of specimens differs greatly, and the load and displacement change nonlinearly. For the specimens containing 0° fiber, the shape of the load displacement curve of the same group of specimens is basically the same, showing a linear change. The shear strength of 0°/0° specimens is the largest, and that of 90°/90° specimens is the smallest. When sticking CFRP for reinforcement, the layering method should be chosen reasonably.

Influence of Fault Crossing Characteristics of New Energy on Transient Voltage

LIU Hui, XIE Wei, GUO Feiyang

2022, 42(6): 99-103. doi:10.3969/j.issn.1008-0198.2022.06.017

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The weak support and low immunity of the new energy power electronic interface have changed the operating characteristics of the power system, now the fault-through characteristics of conventional photovoltaic power plants have not yet been clearly required by standards, and the actual change characteristics of the dynamic reactive current have little research on the impact of the power grid. Based on the measured data of the fault ride-through test of a photovoltaic power station, a simulation model that can effectively reflect the actual fault-through behavior is established under PSASP, and the influence of the dynamic reactive current change characteristics of the photovoltaic power station under fault conditions on the transient voltage of the power grid is studied.The results show that excessive dynamic reacitve current backregulation cluring fault crossing recovery can cause transient overvoltage after fault recovery.

Research on Strategy and Allocation of Standardized Security and Stability Control System

LONG Xuemei, XU Liqiang, XU Biao, OUYANG Fan, LI Hui

2022, 42(6): 104-109. doi:10.3969/j.issn.1008-0198.2022.06.018

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The existing safety and stability control systems are custom designed, which makes it difficult for on-site operation and maintenance and system management. Therefore, it is necessary to carry out standardized design for the safety and stability control system, and study the strategy and distribution of standardized safety and stability control devices. Firstly, the typical structure of the stability control system and the basic functions of the standardized stability control master station, resource collection sub station, information acquisition sub station, new energy execution station and machine cutting execution station are discussed. Secondly, the fixed value configuration and the calculation method of the required cut-off of the standardized stability control system for overload strategy, overload strategy caused by fault and component (section) fault strategy are studied. Then, the distribution mode of the required cut-off quantity and the sending method of the cut-off command of the standardized stability control master station, the resource collection sub station and the execution station are analyzed. Finally, the information exchange between stations of the standardized stability control system is standardized.

Experimental Study on High Voltage Dielectric Loss of Shunt Capacitor for 500 kV Circuit Breaker

TANG Xin, XIONG Yun, MAO Xuefeng, LIAO Zihan, LI Wei

2022, 42(6): 110-113. doi:10.3969/j.issn.1008-0198.2022.06.019

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Conventional dielectric loss tests for coupling capacitor often yield values that exceed the standards. After analysis and verification, it is found that the Garton effect of the insulating medium inside the capacitors is the main reason for the abnormal dielectric loss at low voltage, which cannot reflect the real insulation defect inside the capacitor. Through the high-voltage dielectric loss test, it could be observed that the dielectric loss value of the capacitors changes regularly with increasing test voltage. When the voltage drops back to 10kV, compared with initial values, the dielectric loss values decreased significantly. In this method, the influence of the Garton effect on the actual dielectric loss value has been reduced, which also provides an effective basis for judging whether there is a real insulation abnormality in the breaker capacitance.

Research and Optimization of Low Voltage Fuse Type Selection

XU Zheng, JIANG Pei

2022, 42(6): 114-118. doi:10.3969/j.issn.1008-0198.2022.06.020

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This paper analyzes the selection of fuse for high energy efficiency grade motor, the clamping force of fuse switch, the requirements of capacity reduction and limit temperature rise of fuse under horizontal installation mode,proposes a new method for low-voltage fuse selection, and provides reference for the application of low-voltage fuses.

Analysis and Treatment of Tee Butt Welding Cracks Failure in 1 000 MW Ultra-Supercritical Unit

YANG Chengming, QIU Jian, ZHOU Zhe, YUAN Dan, WANG Wenliang

2022, 42(6): 119-122. doi:10.3969/j.issn.1008-0198.2022.06.021

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There is a whole circle of circumferential cracks in steam-water separator inlet header tee butt weld for a 1 000MW ultra-supercritical unit. Through chemical composition analysis, hardness test, metallographic structure analysis, electron microscope analysis and other experimental methods, the causes of cracks are analyzed.The results show that the reason of reheat crack at weld fusion line is that the welding and heat treatment process is not carried out properly and the structure of tee is unreasonable.Optimizing the structure, welding and heat treatment process of tee can effectively prevent the generation of welding crack of this kind of tee.

Fault Location Method of HVDC Transmission Cable

CHEN Wen, CHEN Kaiping, XIA Xiangyang, XIA Junshan, WANG Ruiqi, HU Xiaozhong

2022, 42(6): 123-128. doi:10.3969/j.issn.1008-0198.2022.06.022

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When the single pole fault occurs in the DC side overhead line of system, the voltage proportion of each frequency band of the single pole line presents different situations due to the different fault pole lines. Therefore, a single pole grounding fault location method of MMC-HVDC system based on fuzzy ratio analysis is proposed in this paper. In this method, the voltage of each frequency band during fault is separated through S-transform. Depending on the different proportion of voltage of each frequency band, the fault pole of the system can be quickly located only by one side of the device, and the weight of the proportion of voltage of each frequency band in the overall ranging can be found by neural network training, so as to finally realize the accurate location of fault location. Finally, PSCAD / EMTDC electromagnetic transient simulation software is used to build the two terminal bipolar flexible DC transmission model. The simulation results verify the accuracy of the proposed identification method and ranging algorithm.

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