abstract：the 6th issue of The Electrical Engineering focuses on practical engineering technology and the frontier development. Academician wangqiuliang of Institute of electrical engineering of Chinese Academy of Sciences is the editor in chief of electrical technology, and Tang Ju, Dean of Electrical Engineering College of Wuhan University, is the executive editor of electrical technology.

The brand Technology Journal of electrical engineering industry sponsored by the Chinese Electrotechnical Society focuses on practical engineering technology and the frontier development. Academician wangqiuliang of Institute of electrical engineering of Chinese Academy of Sciences is the editor in chief of electrical technology, and Tang Ju, Dean of Electrical Engineering College of Wuhan University, is the executive editor of electrical technology.

research and development

Theoretical research and control strategy of a double winding electromagnetic release

Author: Zhang Min; Qian shuangqiu; Wu Zhongqi; Wang Ziyuan

Abstract: power load forecasting can play a guiding and decision-making role in the reasonable planning of power grid. In this paper, data mining technology is used for medium and long-term load forecasting in Nantong area. Firstly, all feeder data in Nantong area are classified by cluster analysis, and the influence degree of external factors on load change is quantitatively analyzed by using correlation analysis and grey correlation analysis; Secondly, the radial basis function (RBF) neural network model based on clustering is established by using the influential factors as the input of neural network, and the load forecasting results are obtained; Finally, compared with the RBF neural network model without considering clustering, the experimental results show that the RBF neural network model based on clustering is more advanced, which significantly improves the accuracy of load forecasting and achieves the purpose of ensuring power supply reliability.

Control strategy of cascaded active power filter based on virtual capacitor compensation

Author: Dai Xiliang

Abstract: cascaded active power filter (APF) can be used for harmonic compensation in medium and high voltage system. In order to improve the poor command tracking ability and resistance to grid voltage interference of traditional direct current control strategy, a control strategy of cascaded APF based on virtual capacitor compensation is proposed. By analyzing and comparing two different compensation methods of command current, it is concluded that the harmonic output control strategy based on command current feedforward compensation has stronger ability to resist grid voltage interference on the basis of ensuring command tracking ability. PSCAD simulation results verify the feasibility and superiority of the proposed method.

Research on direct bus energy storage system based on retired batteries

Author: Zhang Hua; Su Xueneng; Malinson; Wan Chengkuan

Abstract: limited by the cost and capacity of DC-DC module and battery management system, the application of traditional energy storage system in DC distribution network is limited. This paper proposes a direct bus energy storage system based on retired batteries, which can adjust the outlet voltage of the energy storage battery by switching on and off different battery modules with the fluctuation of DC distribution network voltage, so as to realize the purpose of charging and discharging the energy storage battery. Finally, Matlab / Simulink is used to simulate and build the direct bus energy storage system, which verifies that when the voltage of DC distribution network system changes suddenly, the energy storage battery pack can realize the charging and discharging function of the energy storage battery pack by switching on and off each battery pack module.

Characteristic analysis of generator rotor angle control combined with energy storage

Author: Zhang Zhibin; Wei Qiang

Abstract: generator rotor angle control can not only participate in active power regulation and realize frequency recovery without dispatching intervention, but also provide damping torque to suppress low frequency oscillation between regions. The existing rotor angle control uses the steam turbine to provide damping torque, which leads to frequent operation of the control valve and shortens the service life of the steam turbine. Based on the principle that the output electric torque of the generator can be changed by charging and discharging control in the parallel energy storage system, a rotor angle control mode of the generator is proposed to control the turbine and the energy storage at the same time. Among them, the steam turbine is responsible for tracking the load, while the energy storage is responsible for providing damping torque and coping with small load fluctuations. The simulation results show that this mode not only has the advantages of the existing rotor angle control, but also can significantly reduce the number of turbine governing valve actions in load tracking and disturbance.

Multi dimensional information fusion and condition assessment of transformer based on Improved D-S evidence theory

Author: Yuan Yue; Chen Shi; Liu Luyao; Gao Zheng; Shen Tao

Abstract: the correct evaluation of the operation state of transformer can greatly improve the reliability of power supply. In order to improve the accuracy of transformer condition assessment, aiming at the shortage of single parameter selection in traditional transformer condition assessment methods, a multi-dimensional information fusion transformer condition parameter assessment method based on improved evidence theory is proposed. In this method, common transformer type test parameters are selected as on-line monitoring indexes, and then the indexes are normalized. The improved D-S evidence theory is used to fuse the state indexes and build the transformer state parameter evaluation model. The improved D-S evidence theory modifies the composition rules, effectively avoids conflict evidence, and the method can fully integrate multiple information. Experiments show that the accuracy of transformer condition assessment is greatly improved by this method.

Study on the performance of retired LiFePO4 cell

Author: Hou Zhongfeng; Liu Zhan; Ren Min; Lu Shanglin; Wang Jiaju

Abstract: AC withstand voltage test is a necessary test item in manufacturing, installation, handover, maintenance and preventive test of large steam turbine generator. From the aspect of evaluating the main insulation deterioration or thermal breakdown of generator, it is required that the test voltage should be consistent with the working voltage waveform and frequency of generator. In view of this characteristic, a method suitable for generator AC withstand voltage test is designed, which effectively reduces the volume of traditional series resonance equipment, avoids the influence of frequency offset and harmonic of frequency conversion resonance method, and greatly improves the on-site withstand voltage work efficiency of turbo generator.

Problems and solutions of fast switching device in petrochemical industry

Author: Cao Zhen; Dong Guicheng; Zhu Qinghai; Liu Zhixiong; Li Junhong

Abstract: in recent years, with the rapid development of the domestic petrochemical industry, the rapid switching device (referred to as "fast switching") is widely used in the petrochemical industry, which greatly improves the automation level of enterprise control, and the operation effect is remarkable. But at the same time, there are also some new problems, such as low success rate, misstarting, misoperation of protection caused by motor group, cooperation between synchronous generator and fast switching, etc. Complex application scenarios have higher and higher requirements for fast switching, so it is of positive significance to explore new fast switching solutions that are more suitable for petrochemical industry. In this paper, the new application methods and problems are summarized, and combined with certain theoretical analysis and application experience to propose solutions.

Design of an anti electromagnetic interference electrical control cabinet

Author: Cha Xiaochun; Li Longxing; Zhang Yongqiang

Abstract: at present, the main components of the intelligent device in the electrical control cabinet are electronic components and chips, which are very sensitive to electromagnetic interference, and the electromagnetic interference in the substation is very strong, which has a great impact on the operation of the intelligent device. Therefore, it is necessary to design an electrical control cabinet with the function of shielding electromagnetic interference to meet the requirements of the safe and stable operation of the intelligent device. Based on the analysis of the electromagnetic interference source in the substation, this paper designs an electrical control cabinet with electromagnetic shielding function from the selection of cabinet material, cabinet door design, sealing design and grounding design. The design can effectively reduce the impact of electromagnetic interference on the intelligent device in the cabinet and ensure the safe and stable operation of the equipment.

Research on cleaning technology of heliostat in tower photothermal power station

Author: Shen Zhihua

Abstract: according to the needs of heliostat mirror cleaning in tower photothermal power station, this paper analyzes the main causes of heliostat fouling, the form of dust and its impact on the operation of the power station, and designs a mobile heliostat cleaning system by referring to the existing design and operation and maintenance experience of similar photothermal power stations abroad and comparing with the cleaning technology such as on-chip robot. Considering the working environment of heliostat cleaning, the cleaning vehicle is based on the body walking system with high separation angle. Two cleaning methods, spray cleaning and negative pressure dust cleaning, are used to design the mirror field control system and the cleaning vehicle operation control device. Three cleaning modes are designed according to different cleaning conditions, and then the reflectivity test is completed, It provides an important guarantee for the normal operation and maintenance of heliostat and the high efficiency operation of photo thermal power station.

Smart meter fault detection based on smart phone video processing technology

Author: Li Tengteng; Cai Mengjie; Gao Yongfeng; Wang Jiadong; Wang Haibin

Absrtact: the smart meter fault detection device based on smart phone video processing technology uses the smart phone camera to collect the pulse output to realize the power error calibration and fault detection of smart meter. The detection device does not need to open the terminal cover of the meter, it just needs to call the system camera to record. At the same time, it uses the Bluetooth of the smart phone to read the voltage, current and phase measured by the calibrator, and then slices the video into an image for processing to obtain the active pulse output time of the smart meter; At the same time, the measured value read by the Bluetooth of the smart phone is used to accumulate the electric energy, which is compared with the smart meter to complete the error calculation.
Author: Li Cheng; Ma Linrui;; Yang Jianxin; Wang Bo

Absrtact: consistent sorting is one of the key technologies for the echelon utilization of retired batteries. In this paper, the internal and external properties of 15ah decommissioned LiFePO4 battery were studied by external characteristic analysis, capacity test and pulse charge discharge test. The results show that the first step of separation of retired lithium-ion batteries can be preliminarily and rapidly screened by appearance inspection. For the calibration of the actual capacity of the retired battery, the charge discharge current I3 is defined as 80% of the nominal capacity, and the actual capacity of the retired battery is more accurate. Pulse discharge voltage is an important index to judge the consistency of lithium batteries, which can be used as a characteristic index for rapid separation of lithium batteries. Finally, the battery with SOH above 80% and pulse discharge voltage above 2.7V was selected as the battery with good working condition.

Technology and Application

Study on tightening technology of drain plate bolt of transmission line

Author: Wu Zhengshu; Li Shouxin; Zhang Lina; Li Qingyan; Xun Xuefeng

Abstract: in EHV transmission lines, the phenomenon of heating caused by bolt loosening of the drain plate of tension clamp often occurs. Bolt looseness is not only affected by wind vibration, but also closely related to its installation process. It is found that some bolts are loose due to improper installation torque. In this paper, through the design and calculation of the installation torque of the drain plate bolt, combined with the torque preload characteristic test, the torque value and tightening process of the drain plate bolt are studied.

Research on improving the stability of lubricating oil system of large condenser by accumulator

Author: Zhang Shuyun; Zhou Xiang

Abstract: the new generation of large-scale condenser is widely used in UHV power grid construction because of its bidirectional fast dynamic reactive power regulation ability. As an important part of large-scale condenser, the reliable and stable operation of lubricating oil system is very important. At present, the problem of abnormal oil supply pressure exists in the actual operation of the lubricating oil system of large condenser, which seriously threatens the stability of the system operation. In order to solve this problem, this paper proposes a method to improve it by using the accumulator, deeply analyzes the problems existing in the current configuration of the lubricating oil system, and expounds the basic principle, structure and selection calculation of the accumulator, The installation of accumulator can greatly improve the reliability of lubricating oil system of large condenser, improve the operation stability and avoid the risk of tripping, which has important reference value for engineering application.

Principle and operation control of a new high capacity condenser

Author: Su Dongliang; Deng Huayun

Abstract: the new large capacity condenser has the characteristics of absorbing or emitting a large amount of reactive power, and the reactive power value can be quickly and continuously adjusted. It can provide large capacity reactive power reserve for the power grid, improve the reactive power balance of the power grid, effectively improve the stability, operation performance and efficiency of the power grid, and provide effective voltage support in case of power grid system failure. The control strategy of condenser runs through the whole operation process, which directly affects the safety, reliability and economy of its operation. This paper analyzes the control principle and the models of under excitation and over excitation operation stages, and discusses the control strategies, technical difficulties and matters needing attention in the start-up stage, operation stage and shutdown stage of a project's condenser.

Structural analysis of main transformer of large capacity single phase generator

Author: Wang Chungang; Liu Liqiang; Du Zhenbin

Abstract: This paper introduces the common structural types of large capacity single-phase generator main transformer. Taking the technical parameters of a single-phase 315mva / 500kV generator main transformer as an example, three common structural types are compared and analyzed from three aspects of transformer core size, transportation scheme and technical economy, The magnetic flux leakage distribution and insulation characteristics of the three structures are simulated by the software of transformer magnetic flux leakage simulation and wave process calculation. Through the analysis of the economy and safety reliability of different structural types, the advantages and disadvantages of three common structural types and the key factors to be considered in structural selection and design are summarized.

Discussion on leading out mode of high voltage winding of power transformer

Author: Ma Jiangfeng; Ni qianhang

Abstract: the windings of different voltage levels of power transformer are immersed in the oil tank, and the winding leads are led out to the outside of the oil tank through the cable or bushing, and connected with other equipment to realize the transmission of electric energy. This paper introduces several leading ways of winding lead through capacitive bushing, cable bushing and pure porcelain bushing, and analyzes their application, advantages and disadvantages.

A method of AC withstand voltage test for Large Turbogenerator