The brand technical journal of the electrical engineering industry sponsored by the China Electrotechnical Society focuses on practical engineering technology and cutting-edge development. Wang Qiuliang, academician of the Institute of Electrical Engineering, Chinese Academy of Sciences, is the editor-in-chief of "Electrical Technology", and Tang Ju, dean of the School of Electrical Engineering of Wuhan University, is the executive editor-in-chief of "Electrical Technology".
A single-transmitting, multi-receiver magnetically coupled multi-frequency resonant wireless power transmission method
Author:Li Jiangnan;Li Ruihua;Hu Bo.
Summary:At present, the existing multi-load wireless power transfer (WPT) power supply system mainly adopts multiple single-transmitting and single-receiver magnetically coupled power transmission structures based on a single resonant frequency, which has the problems of large volume of transmitting and receiving circuits, high system cost, and poor adaptability of wireless power supply types.
In order to realize the effective transmission of wireless power under the application of multi-frequency and multi-load power supply, a multi-frequency resonant wireless power transmission method based on single-transmit and multi-receiver magnetic coupling structure is proposed, and the influence of pulse-width modulation on the wireless power transfer characteristics of the system is analyzed by establishing a system equivalent circuit model based on single-phase full-bridge inverter and string (SS) resonant compensation network. On this basis, a multi-frequency composite pulse-width modulation (MFPWM) strategy based on unipolar control is designed to realize the effective transmission of multiple magnetically coupled resonant frequency wireless energy at the same time. Finally, based on MATLAB Simulink, the system model is built to verify the feasibility and effectiveness of the proposed multi-frequency resonant wireless power transfer method.
A condition assessment method for heavy-haul railway traction transformer based on health index and non-equivalence grey**
Author: Yang Gehui;Zhao Tongxi;Yao Xin;Zhang Wanqi;Meng Lingyu.
Summary:As the key equipment of the heavy-haul railway traction power supply system, the potential safety hazards caused by the performance degradation of the traction transformer directly affect the railway operation order and driving safety. In view of the shortcomings of the traditional passive maintenance mode, this paper proposes a state evaluation model based on comprehensive health index and iterative ** to realize the optimal maintenance of traction transformers.
Firstly, according to the intrinsic parameters and routine test data of the traction transformer, the state of the traction transformer was evaluated, and a quantitative comprehensive health index was given according to the weightThen, the non-equidistant gray model was used to carry out the remaining life of the traction transformer, and a qualitative analysis was given. According to the on-site maintenance records, the results were compared with the actual transformer status, the accuracy of statistics was calculated, and the method model was iteratively optimized by using the results to improve the evaluation accuracy, so as to establish a model of "monitoring-evaluation-analysis and suggestions" for heavy-haul railway traction transformers. Finally, the data of traction transformer of a heavy-haul railway traction substation from 2015 to 2020 are used to verify the proposed method, and the results show that the method has good feasibility.
Key test methods for AC and DC systems of offshore converter stations
Author:Qiao Mei;Jiang Haitao;Ding Haifeng.
Summary:With the continuous development of flexible DC technology in China, the installed capacity of offshore wind power has been increasing, and the offshore flexible DC transmission voltage has reached 400kV, and the offshore converter station has been successfully applied for the first time. In this paper, the 400kV offshore wind power flexible DC transmission demonstration project in Rudong, Jiangsu Province is studied, and the test method of offshore converter station system is proposed, in order to lay a technical foundation for the subsequent application of offshore wind power DC transmission project.
Day-ahead tariffs based on a hybrid VMD-ICOA-BILSTM model**
Author: Gong Dandan.
Summary:In order to further improve the accuracy of day-ahead electricity prices in the power purchase and sales market, this paper combines variational mode decomposition (VMD), improved coyote algorithm (ICOA) and bidirectional long short-term memory neural network (BILSTM) to provide a new day-ahead electricity price estimation scheme.
Firstly, the VMD is used to divide the original electricity price data into several sub-series to solve the non-stationary problem of the electricity seriesSecondly, in order to solve the shortcomings of the coyote algorithm's slow convergence speed and insufficient optimization performance, the SOBOL sequence was introduced into the coyote initialization, and then the global optimal and local optimal coyote were introduced into the group culture trend of the algorithmThen, the parameters of the Bilstm were optimized by ICOA, and the ICA-BILSTM hybrid model was constructed for subsequenceFinally, the results of each sub-series are summed to obtain the final electricity price. Based on the data of the Danish electricity market, the results show that the proposed method has good accuracy and generalization performance.
Characteristic extraction method of cable partial discharge signal based on NGO-VMD-HHT
Author:Li Siyao;Dong Zhang;Chen Yani;LIU Hui;Yang Hankun.
Summary:In order to solve the problems of difficulty and low accuracy in the partial discharge detection process of cables, a feature extraction method based on Northern Goshawk Optimization Algorithm (NGO)-Variational Mode Decomposition (VMD)-Hilbert-Yellow Transform (HHT) was proposed.
Firstly, the NGO iteration is used to find the optimal decomposition parameters that need to be set during VMD, and the optimal decomposition layer and penalty factor are obtainedThen, the collected signal data is decomposed by VMD to obtain multiple modal components based on the optimal decomposition parametersFinally, the spectral characteristics of the signal are analyzed by using the Hilbert marginal spectrum theory, and then the eigenquantity set of the partial discharge signal is constructed by combining the statistical characteristics and entropy characteristics of the signal. Experimental results show that the proposed cable partial discharge feature extraction method based on NGO-VMD-HHT can effectively decompose the partial discharge signal and construct the corresponding feature quantity set.
Evaluation of the power regulation range of UHVDC peak shaving operation
Author:Li Jun;Yu Xiang;Liu Xinyang;Liu Xiaohui;Zhang Guohua.
Summary:With the increase of the proportion of new energy installed capacity and the decline of the proportion of thermal power installation, the power system peak regulation is facing great pressure, and it is feasible to use the strong power regulation ability of UHV DC to provide peak regulation resources for the power grid, but the flexible adjustment of DC power during peak regulation operation will lead to frequent action of on-load tap-changers and AC filters to reduce their life.
In this paper, we first analyze the ability and constraints of the UHVDC transmission system to participate in the peak shaving operation, analyze the relationship between the number of on-load tap-changers and AC filter actions and the DC power, and then propose a power regulation range evaluation method to ensure that the number of on-load tap-changers and AC filter actions does not exceed the limit during the peak shaving operation of UHVDC. Finally, the model of UHVDC system is built by using real-time digitizer (RTDS), and the results verify the correctness and effectiveness of the proposed method.
Analysis of the causes of cracking of reactor oil conservator pipe of a 1000kV UHV station
Author: Party music;Dong Junqian;Cui Yaru;ZHANG Wei;Hao Jianguo.
Summary:In this paper, a 1 000kV reactor pipe cracking incident was analyzed in eastern Mongolia. In order to find out the cause of the cracking of the pipe and understand the health status of the pipe pipe, a comprehensive test analysis was carried out by using the methods of appearance and morphology analysis, fracture analysis, X-ray digital imaging (DR) fluoroscopy detection, chemical composition analysis, metallographic microstructure detection, mechanical property testing and strength verification calculation.
The results show that the cracking occurs at the welding toes on both sides of the fillet weld of the branch pipe connected to the high-voltage test and assembly on the connecting pipe, and the thickness deviation of the pipe wall is large, and the fillet weld of the branch pipe has different degrees of welding defects such as slag inclusion, porosity and lack of penetrationThe fracture of the cracked manifold pipe branch is cracked on the outer wall, and most of the area on the fracture is the expansion area, and the "beach-like" fatigue glow can be observed macroscopically in the expansion area, and the obvious fatigue bands can be observed on the microscopic level, which is a typical fatigue fracture, and there are obvious defects of the full decarburized layer on the inner and outer surfaces of the pipe, which reduces the fatigue strength of the pipe.
A kind of substation secondary anti-error function realization method
Author: Kwong Daihua.
Summary:If the secondary equipment of the substation is misoperated, it is easy to cause the rejection and misoperation of the relay protection, which will cause power grid accidents. At present, the anti-error measures of the secondary equipment in the substation are relatively lacking, so this paper proposes a method to realize the anti-misoperation of the secondary equipment in the substation, through a comprehensive analysis of the types and functions of each secondary equipment in the substation, and expounds the implementation ideas of the secondary anti-misoperation function from the aspects of secondary equipment modeling, secondary equipment state acquisition, secondary anti-error rules, and secondary anti-error algorithms, and gives a secondary anti-error solution. The practical application of the project shows that the integration of the secondary anti-misoperation function in the anti-misoperation and locking system of the substation can avoid the misoperation of the secondary equipment, improve the safe operation level of the power grid, and provide effective technical guarantee for the safe operation of the equipment.
Information flow analysis of 500kV circuit breaker latching recloser of intelligent station
Author: Chi Xiang;ZHAO Kang;Shang.
Summary:This paper analyzes the principle of 500kV circuit breaker latching and reclosing, sorts out the information flow of 500kV circuit breaker latching and reclosing in intelligent substation under IEC 61850 standard, and explains the redundancy design of 500kV circuit breaker latching and reclosing information flow of intelligent station. On this basis, a case of inconsistent signals for maintenance caused by inconsistent transmission due to the inconsistent configuration of the 500kV circuit breaker protection latching reclosing virtual circuit was analyzed. Finally, suggestions are put forward for the relevant work on the substation site, which provides a reference for the protection commissioning and related operations of 500kV circuit breaker.
Analysis and solution of DC voltage anomaly of an ultra-high voltage direct current transmission project
Author:Jia Xuantao;Xiong Fei;Zhang Yuduo.
Summary:: During the test of an ultra-high voltage direct current transmission engineering system, the data of the DC divider on the rectifier side is abnormal, especially when the power is reversed, which is inconsistent with the electrical principle. According to the information of AC voltage, DC voltage, current, tap-changer gear and trigger angle (arc extinguishing angle) under different power levels, power forward and reverse transmission conditions during the system test, the possible causes of the problem are analyzed from the perspective of theoretical calculation, and the corresponding simulation test is carried out, and the test results are basically consistent with the theoretical calculation. Finally, the inverter side DC divider is used for calibration and compensation, so that the actual voltage value of the DC system is consistent with the complete set of design, so as to ensure the safe and stable operation of the UHVDC project.
The application of chain trusted start-up in HVDC transmission control and protection host
Author:Li Yuepeng;Kang Jingjing;ZHANG Jian;Ji Chaoqiang.
Summary:In order to solve the problem of weak security protection ability of the control and protection host in HVDC transmission, a trusted root of trust was constructed based on the Trusted Platform Module (TPM) security chip, and the national cryptography algorithms SM2, SM3 and SM4 were used to construct the root of trust and use it for identity authentication. The overall design of the system establishes a complete chain of trust through identity authentication and digital signature from the two aspects of hardware boot and software boot, and realizes the chain trusted boot of the whole process from hardware boot, system loading to system operation of the control and protection host. Experimental results show that the proposed scheme can identify the risks of firmware tampering and identity forgery, realize the safe start of the control and protection host, and improve the overall protection level of the HVDC transmission system.
Research on dual-engine redundant switching technology of frequency converter for nuclear power main pump
Author:Wang Xiankun;Wu Xing;Song Wenke;Li Biao;Zhu Wei.
Summary:As the core electric drive equipment of the main pump motor of the nuclear power plant, once the frequency conversion speed control equipment fails, it will cause very serious consequences to the production and related processes. In view of this, this paper proposes a dual-machine redundant drive scheme for inverters, which realizes the redundant backup of the whole inverter by driving one motor through two inverters, and when the main inverter driving the motor fails, it can be automatically switched to the drive output of the standby inverter in a short time (150ms) to ensure the continuous and stable operation of the motor. This dual-engine redundant switching scheme can provide an important guarantee for the stable operation of nuclear power plants and reduce potential risks.
Research on the grounding mode of sheath of 35kV single-core cable based on the analysis of induced voltage electric shock event
Author: Zhu Lijiao;Cheng Jinran;Yin Xingjian.
Summary:Based on the analysis of induced voltage electric shock event, according to the selection principle of the grounding mode of the sheath of the 35kV single-core cable and the calculation of the induced voltage of the sheath, the reasonable grounding method of the sheath of the 35kV single-core cable in the subway power supply system is given, so as to reduce the system failure rate and optimize the equipment management and operation.