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International Conference on Critical Infrastructures, CRIS

作者： Yagang Zhang Zengping Wang Jinfang Zhang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China

The faults in electric power system can not be completely avoided. When power system operates from normal state to failure or abnormal operates, its electric quantities may change significantly. Our researches indicate that the variable with the biggest coefficient in principal component usually corresponds to the fault. Therefore, utilizing real-time measurements of PMU, basing on principal components analysis technology, we have completed the fault location of electric power system. Of course, because of the complexity of different types of faults in power system, there still exists enormous problems need a close and intensive study.

关键词： Principal component analysis Covariance matrix Fault location power system dynamics Eigenvalues and eigenfunctions Complexity theory

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Reliability evaluation for distribution system with distributed generators

Reliability evaluation for distribution system with distribu...

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International Conference on Critical Infrastructures, CRIS

作者： Yuqin Xu Yingchao Wu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China

ISBN: (纸本)9781424480807

Distributed generator (DG), with its flexible power generation, environment-friendly advantages has been more widely used in distribution system, which has brought some influence to the traditional distribution network reliability evaluation. In this paper, two different models for conventional DG and wind turbine generator (WTG) are established for reliability evaluation, based on different energy sources and operation characteristics. This paper presents a technique to obtain the WTG output using statistical wind speed information, considering to the intermittent characteristics of wind power. On this basis, an improved minimal cut set algorithm is proposed to evaluate the reliability of distribution network with DG. Finally, the simulation of a typical distribution line with DG verifies the validity of this method.

关键词： Reliability power system reliability Indexes Wind speed power generation Generators

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New Technologies of Modular Multilevel Converter for VSC-HVDC Application

New Technologies of Modular Multilevel Converter for VSC-HVD...

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IEEE PES Asia-Pacific power and Energy Engineering Conference (APPEEC)

作者： Ke Li Chengyong Zhao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China

This paper presents some new technologies of modular multilevel converter (MMC) for VSC-HVDC application. The origin of modular multilevel VSC and its essential working mechanism are clarified in detail. Then, the starting of MMC under de-energized condition is discussed and a simple but effective control scheme is proposed. Concerning the drawbacks of traditional PWM modulation technologies, i.e., SVPWM and SHPWM, an improved modulation control technology based on waveform approximation is presented. The proposed modulation technology makes the individual semiconductors have much lower switching frequency (50 Hz) resulting in lower switching losses and, consequently, lower total losses of the transmission system compared to 2 or 3-level VSC. The technologies and conclusions are validated by simulations in PSCAD/EMTDC. The theory analysis and simulation results indicate that these new technologies have great potentiality in the application of VSC-HVDC projects in future.

关键词： power conversion Voltage Space vector pulse width modulation Capacitors Clamps Semiconductor diodes Switching converters Educational technology Paper technology Switching frequency

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Prony analysis of electrical transient characteristics of AC system during HVDC commutation failure

Prony analysis of electrical transient characteristics of AC...

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International power Engineering Conference (IPEC)

作者： Rulian Zhang Chengyong Zhao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China

With the development of High Voltage Direct Current (HVDC) transmission, the impact of DC system on AC relay protection becomes more prominent. So it becomes more important to research electrical characteristics of AC system under DC faults. In PSCAD/EMTDC environment, the inverter commutation failure resulted from short circuit faults in AC line is simulated based on the electromagnetic transient model of Shandong grid containing Ningdong-Shandong DC transmission system. Prony algorithm is applied to analyze the electrical transient characteristics of AC system during commutation failure. The coincidence of fitted waveform and simulated waveform verified the validity of prony algorithm. Prony analysis results show that DC system injects a large number of inter-harmonic components into the inverter side AC system during commutation failure, and the distortion of the parallel line current is more serious than that of the fault line current, so the impact of DC system on the AC relay protection devices equipped on the parallel line is greater.

关键词： HVDC transmission Algorithm design and analysis Transient analysis Harmonic analysis Inverters power system harmonics

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Application of Cooperative Game Analysis in Combination Evaluation of power Quality

Application of Cooperative Game Analysis in Combination Eval...

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2010年中国国际供电会议(CICED 2010)

作者： Guodong Li Gengyin Li Ming Zhou Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power UniversityChangping 102206BeijingChina

ISBN: (纸本)9781457700668

Cooperative game theory is firstly introduced into the comprehensive assessment of power quality,and a new model for combination evaluation of power quality is established based on cooperative game. The model takes into account the advantages of 4 kinds of single assessment method. By calculating the characteristic function values of various combinations to get the Shapley value of each assessment method,and then the weight value of each method in combination union can be determined,so that power quality assessment conclusion could be optimized. The conclusion also reflects the information of evaluation object from different angles. The simulation results show that the combination evaluation method with good accuracy can be effectively applied to the comprehensive assessment of power quality.

关键词： Combination evaluation comprehensive evaluation cooperative game power quality Shapley value

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An analytical method for studying transient torques

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2010年第7期30卷 70-76页

作者： Chen, Wu-Hui Bi, Tian-Shu Yang, Qi-Xun Deng, Ji-Xiang Xue, An-Cheng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Ministry of Education Changping District Beijing 102206 China Electrical Engineering College Northeast Dianli University Jilin 132012 Jilin Province China

Based on the modal series method, the first-order and second-order solutions of torques were deduced. An analytical method was established for analyzing torsional dynamics. It can directly represent torsional dynamics with the physical concepts. The quantitative index was given for analyzing the feasibility of the solutions. Furthermore, the nonlinearity modal indices and contributor factors of torques were defined based on the second-order solutions, and they were used to study the impact of nonlinear modal interactions on the transient torques. The fundamental-mode nonlinearity index describes the effect of nonlinear modal interactions on the initial amplitudes and phase angles of fundamental modes. The combination-mode index represents the strength of interactions between fundamental combination modes and combination modes. The nonlinearity contribution factors embody the contributions of the fundamental and combination modes to the second-order solutions of torques. The IEEE First Benchmark system was adopted to carry out this study, and some new viewpoints were obtained. © Chin. Soc. for Elec. Eng.

关键词： Torque

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A study of transient-based protection using wavelet energy entropy for power system EHV transmission line

A study of transient-based protection using wavelet energy e...

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International Conference on Wavelet Analysis and Pattern Recognition (ICWAPR)

作者： Ming-Yu Yang Yu-Kun Yang Key Laboratory of Power System Protection Dynamic Security Monitoring and Contro1 under Ministry of Education North China Electric Power University Baoding China

Wavelet energy entropy has a small calculation amount, and it has a unique sensibility to slightly change of the dynamic system parameters. This paper presents a novel transient-based protection for power system EHV transmission line, which employ the value of wavelet energy entropy to reflect the different energy distribution between internal and external fault. The basic principle of the protection is according to the attenuation effect of busbar capacitance and line trap to the high-frequency components. Simulation results show that the proposed protection criterion has high sensitivity and reliability, and capable of providing correct responses under conditions of different fault types, positions, path resistances, and inception angles.

关键词： Wavelet transforms Entropy Wavelet analysis Transient analysis power transmission lines

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Research on PID parameters optimization of synchronous generator excitation control system

Research on PID parameters optimization of synchronous gener...

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International Conference on Critical Infrastructures, CRIS

作者： Yuan Cao Jin Ma Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing P.R.China

Synchronous generator excitation control system is one of the most important parts of power system control. And as PID control is one of the first developed and the most widely used control schemes in excitation system, its parameters tuning problem has been highly concerned. Since MATLAB genetic algorithm toolbox has the characteristics of strong robustness and efficient optimization, this paper first establishes a mathematical model of generator excitation system, and then uses ITSE index of terminal voltage step response curve as the optimization index, computes the fitness function based on SIMULINK platform, and uses MATLAB genetic algorithm toolbox to optimize PID parameters of synchronous generator excitation control system. Applying this method to a power plant's synchronous generator excitation system, results demonstrate that dynamic characteristics are improved greatly.

关键词： Generators Optimization MATLAB Indexes Control systems Transfer functions Voltage control

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Stochastic parallel algorithm based evaluation of available transfer capability

Stochastic parallel algorithm based evaluation of available ...

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2010 5th International Conference on Critical Infrastructure, CRIS 2010

作者： Wei, Junqiang Li, Gengyin Zhou, Ming Lo, K.L. Department of Mathematics North China Electric Power University Changping District Beijing 102206 China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Changping 102206 Beijing China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow G1 1XW United Kingdom

ISBN: (纸本)9781424480814

In practical power markets, Available Transfer Capability (ATC) is crucial for transmission customers, system operators and power marketers to make a good choice. It is an indication of the expected transfer capability remaining on the transmission network. In order to assure the secure, economic, stable and reliable operation of power systems, the assessment of ATC should be carried out instantly. Most of the existing ATC calculation are mainly focused on AC power systems and based on deterministic techniques. As high performance computing has been extensively used in scientific computation and technology, less work has been done on evaluation of ATC by using parallel algorithm. This paper is dealing with the evaluation of ATC by stochastic parallel algorithm in an AC power system. Due to the stochastic nature of power system behaviors, it is important to assess ATC from a statistical and risk analysis point of view. Considering the dynamics, time-varying and uncertainties of power systems, several statistical indices is presented to evaluate ATC. They are calculated based on Monte Carlo simulation and parallel computing. The system operation states can be simulated by Monte Carlo method, and the parallel algorithm based on MATpower (A MATLAB™ power system Simulation Package) is developed. Case study with an IEEE 30-bus power system is used to verify the presented approach. Five-number summary and other statistical indices of ATC are calculated. The results show that the proposed method can elapse shorter computation time and it is more effective and practical. Some new attractive issues are suggested at the end. © 2010 IEEE.

关键词： Parallel algorithms

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Monte Carlo simulation based assessment of available transfer capability in AC-DC hybrid systems

Monte Carlo simulation based assessment of available transfe...

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2010 5th International Conference on Critical Infrastructure, CRIS 2010

ISBN: (纸本)9781424480814

Available transfer capability (ATC) is defined as a measure of the system's capability for transfers of power for further commercial activity, over and above already committed uses. In practical power markets, ATC can provide important information for transmission customers, system operators and power marketers. The assessment of ATC should be carried out to assure the secure, economic, stable and reliable operation of power systems. Most of the existing ATC calculation are mainly focused on AC power system and based on deterministic techniques. As high voltage direct current (HVDC) power distribution systems have been extensively used in modem transmission network, less work has been done on evaluation of ATC in AC-DC hybrid power system. This paper is dealing with the evaluation of ATC for the integration of HVDC link with an AC power system. The mathematical model of ATC for AC-DC hybrid power system is proposed. Due to the stochastic nature of power system behaviors, it is important to assess ATC from a statistical and risk analysis point of view. Considering the dynamics, time-varying and uncertainties of hybrid power systems, several statistical indices are presented to evaluate ATC and they are calculated based on Monte Carlo simulation. States of system operation can be simulated, and the algorithm based on MATpower (A MATLAB™ power system Simulation Package) is developed in the environment of MATLAB 7.5. Case study with a modified IEEE 30-bus AC-DC hybrid power system is used to verify the presented approach. Sequential solution method is employed to deal with the AC-DC power flow. Fivenumber summary and other statistical indices of ATC are calculated. The results show that the proposed method is effective and practical. The research achievements are undergoing to transfer to the application in other hybrid power systems with different control style, and some new problems are suggested at the end of paper. © 2010 IEEE.

关键词： MATLAB

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