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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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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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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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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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Research on soft regulation strategy of VSC-HVDC systems

Research on soft regulation strategy of VSC-HVDC systems

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IEEE General Meeting power& Energy Society

作者： Song Wang Gengyin Li Ming Zhou Zhe Zhang Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

ISBN: (纸本)9781424465491

Based on power electronic converting current devices which can be controlled quickly, VSC-HVDC system can regulate active power, reactive power, DC voltage, and line voltage flexibly. Different regulation strategies have different influences on the power system stability. A worse regulation strategiy may lead to sharp fluctuation of electrical measurements and longer regulation time, which is harmful for the system stability. It is worse when faults happen during the regulation. The traditional regulation strategy is that the reference value of regulation is set to the goal value directly, sometimes the change is very serious like the reversal of power flow, and the electrical measurements may have sharp fluctuation during the regulation. Different from the traditional regulation strategy, a new regulation strategy, called soft regulation strategy, was presented in the paper, which can minish the fluctuation of electrical measurements and shorten the regulation time. The soft regulation strategy is helpful for the system stability and the device security. The soft protection strategy for serious impact from AC faults is also presented, by which the fault terminal is softly closed and the non-fault terminal works right as before, while the DC voltage can be kept, which increases the efficiency of VSC-HVDC system and makes preparation for restoration. Simulations performed in PSCAD/EMTDC verify the proposed regulation strategy.

关键词： Circuit faults Voltage control power conversion Reactive power Electric variables measurement Fluctuations

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Zonal pricing model of voltage quality service based on sag energy index

Zonal pricing model of voltage quality service based on sag ...

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IEEE General Meeting power& Energy Society

作者： Guodong Li Gengyin Li Ming Zhou Xiaodong Yang Key Laboratory of Power System Protection and Dynamic Society Monitoring and Control North China Electric Power University Beijing China

ISBN: (纸本)9781424465491

The paper proposes voltage quality service, and makes comprehensive evaluation to sag energy indices to arrive at a quantitative description, then makes differential pricing of voltage quality service combined with market-oriented theory. It puts forward zonal pricing model of voltage quality service based on sag energy indices, as the foundation of comprehensive assessment of power quality and price amendment, and ultimately accomplishes pricing by power quality. It gives raw data according to Monte Carlo simulation, and then proceeds to fuzzy clustering partition of load points. After determining comprehensive weights of districts, it gives assessment value of scoring, and finally designs different correction function to tariff amendment. The simulation results show that the method of tariff amendment proposed in the paper, is applicable to needs of different users with practicality and effectiveness, and is conducive to the development of electricity market.

关键词： Voltage fluctuations Pricing Indexes Electricity Electricity supply industry power quality

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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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A study based on DC chopper excitation system

A study based on DC chopper excitation system

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International Conference on Computational Problem-Solving (ICCP)

作者： Guofei Zhang Huilin Wang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education School of Electrical and Electronic Engineering North China Electric Power University Beijing China

A new self-shunt excitation control method has been brought in this paper, which is about how to use DC chopper that is composed with full controlled switch device IGBT to regulate exciting voltage. This new method replaces traditional method which is adopted controlled rectifier by thyristor. Exciting voltage refers from terminal voltage by exciting transformer, and then it goes through uncontrollable rectifier circuit and switches to DC voltage. This DC voltage is used for DC chopper. We can control duty cycle of IGBT to change output voltage and hold terminal voltage steady. In this paper, the conclusion of DC chopper output current proportioned with duty cycle is proved by simulation in PSCAD. And it also proves that it can maintain terminal voltage stability in steady state operation by the control of trigger angle of IGBT.

关键词： Insulated gate bipolar transistors Voltage control Choppers Generators control systems Electrodes power systems

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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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