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International Conference on Advanced power system Automation and Protection (APAP)

作者： Min Xie Wei Zhang Ludeng Liu Xin Jia Bin Wang Xinzhou Dong Dispatching and Controlling Center of Anhui Electric Power Company State Grid Hefei China Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University China

ISBN: (数字)9781728117225

ISBN: (纸本)9781728117232

The beat frequency characteristic of the recovery voltage of fault phase in the case of single-phase grounding transient fault happening to line with the shunt reactors is analyzed. Besides, the paper analyzes the reason of no beat frequency phenomenon of transient fault happening to line without shunt reactor. The AC power networks with metallic grounding fault and arc grounding fault are analyzed by simulation. The recovery voltage of single-phase grounding fault in AC/DC hybrid power grid is studied by PSCAD. The new problems of the adaptive re-closure in AC-DC hybrid power system are discussed. Then the follow-up ideas to solve several existing problems are also presented.

关键词： Circuit faults Inductors Shunts (electrical) Transient analysis Integrated circuit modeling Grounding Capacitance

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XLPE cable health assessment based on Relief-F feature weighted FSVM

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IOP Conference Series: Earth and Environmental Science 2021年第1期675卷

作者： Xiaohuan Wu Yang Liu Liqun Wang Xinzhuo Ren Xianjun Tan Hangzhou Power Equipment Manufacturing Co. Ltd. Hangzhou 310018 China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education(Northeast Electric Power University) Jilin 132012 China

For the cross-linked polyethylene (XLPE) cable health status assessment process, there are noise data for each feature parameter and the importance of each dimension feature is difficult to determine, which leads to deviations in the cable status assessment results. An XLPE cable health assessment algorithm based on Relief-F feature weighted fuzzy support vector machine is proposed. The Relief-F algorithm is used to calculate the importance of each dimension feature. The feature quantity that is weakly related to the evaluation of the health status of the XLPE cable is deleted. Furthermore, the fuzzy support vector machine is used to evaluate the health status of the XLPE cable, which gives the noise data a smaller degree of membership and reduces the influence of the noise data on the evaluation results. Experimental analysis shows that this method can accurately assess the health status of XLPE cables. It can provide a reference value for relevant departments to carry out cable maintenance and replacement work and save the human resources, and material resources required for maintenance and replacement of cables.

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Prediction of dissolved gas in power transformer oil based on LSTM-GA

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IOP Conference Series: Earth and Environmental Science 2021年第1期675卷

作者： Xin Zhang Shengyuan Wang Yijun Jiang Feifei Wu Chenming Sun Hangzhou Power Equipment Manufacturing Co. Ltd. Hangzhou 310018 China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education(Northeast Electric Power University) Jilin 132012 China

Because the change process of the content of dissolved gas in transformer oil is fluctuating and is affected by many factors such as oil temperature and external environment, the gas content does not increase exponentially and is nonlinear and non-stationary. This feature determines the current Prediction technology cannot accurately predict the concentration of dissolved gas in transformer oil. To improve the prediction accuracy of the dissolved gas content in the transformer oil, more accurately evaluate the transformer status and customize the entire preventive plan under the alarming development trend of the transformer, to minimize the prediction error, this paper proposes a transformer combining genetic algorithm and long short-term memory (LSTM)neural network Prediction model of dissolved gas content in oil. The genetic algorithm (GA) is used to optimize look back(lb), lstm nets(ls), epochs(ep), and the dropout(dp), and then the genetic algorithm is combined with the long short-term memory neural network. The gas content is predicted. This model overcomes the problem of low prediction accuracy caused by selecting parameters based on experience. The analysis result of the calculation example shows that compared with the traditional prediction algorithm, the proposed method can better track the change law of the dissolved gas concentration in the oil, improve the prediction accuracy, and provide a strong guarantee for the safe and stable operation of power transformers.

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Phase-shift full bridge power supply based on SiC devices

Phase-shift full bridge power supply based on SiC devices

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作者： Liu, Guobing Wang, Kui Qu, Cangqi Liu, Shaogang Jia, Qi Li, Yongdong Beijing Shengfeifan Electronic System Technology Development Co. Ltd. Beijing China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

In order to accurately obtain the switching characteristics of SiC MOSFET in practical application, a dual pulse test circuit is used to test the SiC MOSFET in this subject. By analysing the double pulse test circuit and taking into account the parasitic parameters, the effects of different gate resistances (Rg) and the capacitance between gate and source (Cgs) on the switching characteristics of the SiC MOSFET are summarised. Also, a phase-shifted full-bridge power supply based on SiC device is designed, which can be changed from 270 V direct current (DC) to 220 V alternating current (AC)/50 Hz, which consists of two stages. The first stage is the phase shifted full bridge ZVS DC/DC converter, which will boost the 270 V DC to the 350 V DC;the latter is a single-phase full bridge inverter, and the 350 V DC will be converted to the 220 V AC/50 Hz. The power supply uses the SiC MOSFET as the switch tube, which can reduce the switching loss, improve the switching frequency and reduce the volume of the transformer. A rectifier circuit using a SiC Schottky diode, with almost no reverse recovery process, greatly reduced the transformer side parasitic oscillation and improved the efficiency of the power supply. In this study, the design method of the parameters of the power supply is described in detail. Finally, the rationality of the design of the power supply parameters is verified by MATLAB/Simulink simulation and experimental prototypes. © 2018 Institution of Engineering and Technology. All rights reserved.

关键词： MATLAB

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Investigate the influence of renewable energy penetration on the electricity market equilibrium 8

Investigate the influence of renewable energy penetration on...

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8th Renewable power generation Conference, RPG 2019

作者： Li, Chenchen Yang, Zhifang Zhang, Yichi Yu, Juan Zou, Peng State Key Laboratory of Power Transmission Equipment and System Security and New Technology College of Electrical Engineering Chongqing University Chongqing China CQU-UC Joint co-op Institute Chongqing University Chongqing China Power Dispatch and Control Center Shanxi Electric Power Company of SGCC Shanxi China

ISBN: (数字)9781839531248

ISBN: (纸本)9781839531255

China is performing the electricity market reform. With the increasing penetration of renewable energy, it is important to understand how the renewables influence the market performance. Renewables are different from the traditional generators in two aspects: 1) the marginal costs of renewable are small;2) renewables cause fluctuations and increase the requirement of auxiliary service. In this paper, we analyse the influence of renewables on the market equilibrium. A multi-period Supply Function Equilibrium (SFE) model is formulated, where the upper level model maximizes individual profits of market participants, and the lower level model minimizes the market operational costs. To avoid the infeasibility of the equilibrium model, the relaxation of the complementary slackness condition is utilized. This paper exhibits how the increase of renewable penetrations affects the optimal bidding and profits of other market participants, including the traditional generators, hydro generator, and storage. The influence of renewables on the market equilibrium is exhibited as well. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Profitability

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Short-term Optimized Operation of Multi-energy power system Based on Complementary Characteristics of power Sources

Short-term Optimized Operation of Multi-energy Power System ...

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2019 IEEE PES Innovative Smart Grid Technologies Asia, ISGT 2019

作者： Xiao, Bai Zheng, Jia Yan, Gangui Shi, Yonggang Jiao, Mingxi Wang, Yao Dong, Ling Wang, Maochun Yang, Hongzhi Key Laboratory of Modern Power System Simulation and Control Renewable Energy Technology Ministry of Education Northeast Electric Power University Jilin China Tonghua Power Supply Company State Grid Jilin Electric Power Co. Ltd. Tonghua China Changchun Power Supply Company State Grid Jilin Electric Power Co. Ltd. Changchun China State Grid Qinghai Electric Power Company Xining China

ISBN: (纸本)9781728135205

Aiming at the problem that uncertain power sources bring fluctuation to power system and cause lots of wind and photovoltaic curtailment, a short-term optimized operation method of multi-energy power system based on complementary characteristics of power sources is presented. The complementary mechanism of multi-energy power system is established. Based on the complementary mechanism, mathematical models of complementary objectives and complementary demands are established. Define renewable energy complementary power source. To minimize complementary demands, the capacity matching ratio of hydropower in renewable energy complementary power source is determined. According to the complementary objectives, a hierarchical optimal operation strategy for multi-energy power system is proposed. Particle swarm optimization is used to solve the optimization objective function. Taking a provincial power grid in northwest China as an example, the results show that the strategy makes full use of the complementarity of power sources and has the benefit of energy saving. © 2019 IEEE.

关键词： Energy conservation

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Modeling and simulation analysis of dual-rotor vibration system with multiple faults

Modeling and simulation analysis of dual-rotor vibration sys...

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Society for Machinery Failure Prevention Technology Conference 2018: Intelligent Technologies for equipment and Human Performance Monitoring, MFPT 2018

作者： Yang, Yizhou Liu, Chao Jiang, Dongxiang Yang, Wenguang State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing100084 China

Dual-rotor system is an important rotor form in rotating machinery like gas turbine engine. Its complex structure results in rich dynamical behaviors and more probability to failure. The modeling and simulation of the dual-rotor system can help to understand its dynamic characteristics and provide theoretical support for the design, operation and maintenance. In this paper, a dynamic model of a dual-rotor system with multiple rotor faults is established. The dual-rotor vibration model without any fault is built by finite element method, where the two shafts are connected by an inter-shaft bearing and nonlinear models of rolling element bearing and squeeze film damper are considered. The numerical integration method of Newmark-β is used to obtain the steady-state vibration response of the system. Then rotor faults are introduced to the system model, including unbalance, misalignment, looseness and rub-impact. The steady-state responses of single faults in the dual-rotor system are analyzed and typical fault features are obtained. Then coupling characteristics between different rotor faults, and the influences of the squeeze film dampers on the dynamic characteristics and fault features of the system are studied. © 2018 Proceedings of the 9th International Symposium on Imprecise Probability.

关键词： Rotating machinery

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FPGA-based Adaptive Variable Step MPPT Real Time simulation for Photovoltaic systems

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IOP Conference Series: Earth and Environmental Science 2021年第1期645卷

作者： Ruxun He Shouxiang Wang Chunyu Zhang Qi Ma Key Laboratory of Smart Grid of Ministry of Education Tianjin University Tianjin 300072 China Tianjin Key Laboratory of Power System Simulation and Control Tianjin University Tianjin 300072 China State Grid Tianjin Electric Power Company Tianjin 300010 China

In order to obtain more output power, maximum power point tracking (MPPT) control technology is usually designed to track the maximum power of photovoltaic (PV) array. The traditional power disturbance observation method tends to cause power oscillation loss, so an adaptive variable step algorithm is presented to balance the tracking accuracy and speed of PV system. Different from off-line simulation, the overall model is built on FPGA to complete the real time digital realization of MPPT control for PV system. Finally, the model is simulated and verified by ModelSim software. The experimental results show that the system can track the maximum power more quickly and accurately in real time.

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CCF early warning method of LCC-HVDC based on XGBoost algorithm

CCF early warning method of LCC-HVDC based on XGBoost algori...

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8th Renewable power generation Conference (RPG 2019)

作者： Zhizhong Li Bin Wang Haigang Wang Bin Yu Min Xie Shi Chen Xinzhou Dong Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China State Grid Anhui electric power company Hefei 230061 China

ISBN: (数字)9781839531248

ISBN: (纸本)9781839531255

The lack of analytical mechanism of continuous commutation failure (CCF) process hinders the development of CCF early warning algorithm and further obstructs the coordination strategy of relay protection between AC and DC size in hybrid grid. However, summarizing the protection threshold of CCF in the form of electrical quantity analytically under different fault types is a nontrivial pattern recognition problem. To overcome the difficulty of directly analysing the electromagnetic process of CCF, a statistical learning modelling approach is adapted to propose a CCF warning system, in which XGBoost algorithm was used as the backbone to regress on the relationship between AC/DC electrical quantities and the possibility of the occurrence of CCF. The design of the feature vector in XGBoost-based classifier considers not only the analytical expression of key electrical quantity during single commutation failure but also the important state variable of control system. Additionally, a special data windowing method was proposed to enrich of information encoded by the feature vector while ensuring the speed requirement posed by the protection system. Validation on multi-fault scenes simulation shows that the proposed early warning system can trigger warning signal correctly with sufficiently small measured data required, proving the practicability in engineering practice.

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Novel ZnO Varistors for Dramatically Improving Protective Effect of Surge Arresters

Novel ZnO Varistors for Dramatically Improving Protective Ef...

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International Conference on Lightning Protection (ICLP)

作者： Pengfei Meng Yao Zhou Jinbo Wu Jun Hu Jinliang He State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

The insulation level of power apparatus is based on the protection level of overvoltage in power systems. Deeply suppressing the switching overvoltage of UHV systems will reduce the manufacturing cost and technical bottlenecks of UHV power apparatus. We studied the effects of multi-elements doping on the electrical properties of ZnO varistors co-doped with Al2O3, Ga2O3, and In2O3 Scanning electron microscopy, current-voltage testing, capacitance-voltage testing, and X-ray diffraction were performed. The results showed that the residual voltage ratio of sintered varistors decreased as the indium dopant concentration was increased. The samples with 0.03 mol % indium, 0.2 mol % aluminum, and 0.42 mol % gallium showed excellent overall performance, exhibiting a nonlinear coefficient of 61.2, a leakage current of 1.63 μA /cm2, a 1-mA residual voltage of 435 V/mm, and a residual voltage ratio of 1.52. These optimized properties will be of great utility in the manufacture of metal oxide arresters. The protective effects of this kind of novel surge arresters for lightning and switching overvoltage in UHV systems are analyzed. With the low residual voltage ZnO varistors applied to surge arresters will dramatically improving the protective effect of surge arresters, to realize the target to deeply suppress the lightning and switching overvoltages, and then reduce the insulation level and manufacturing bottleneck of UHV power apparatus.

关键词： Zinc oxide II-VI semiconductor materials Arresters Varistors Indium Surges

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