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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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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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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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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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Analysis on Parameters Selection of Injection Circuit of Differentiation Cascade type controllable Custom power Quality Disturbance-Generator

Analysis on Parameters Selection of Injection Circuit of Dif...

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

作者： Zhe Sun Chunlin Guo Yonghai Xu Xiangning Xiao Yingying Liu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control of Ministry of Education North China Electric Power University Beijing P. R. China

Theoretical and simulated analysis on the injection circuit parameters of the controllable Custom power Quality Disturbance-Generator which is designed as differentiation cascade type has been done. The topology has three modules: fundamental-frequency module, high-frequency module and rectifier module. The theoretical analysis results have shown that the regulation precision of output of the fundamental-frequency module, the voltage level of the high-frequency module, the current tracking performance and the harmonic current circumfluence in the high frequency module will be influenced by the linking inductor of the fundamental-frequency module. The harmonic current output of the high-frequency module will be influenced by the linking inductor of the high-frequency module. Furthermore, taking a capacitor in series with the inductor in the injection circuit of the high-frequency module is an effective method to reduce the voltage level of the high-frequency module. However, this method will influence the amount of the fundamental frequency current that generated by fundamental-frequency module. The simulations have been carried out to show the correctness of the theoretical analysis and provide a reference for parameters selection of the injection circuit and the design of the device's control methods.

关键词： power quality Inductors Analytical models Circuit simulation Voltage Frequency Joining processes Circuit topology Rectifiers Harmonic analysis

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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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Q impact of load characteristic on dynamic security region of power system

Q impact of load characteristic on dynamic security region o...

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International Conference on power system Technology (powerCON)

作者： Zhenbo Cao Ancheng Xue Jin Li Tianshu Bi 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

DSR (dynamic security region) is one of the direct methods focusing on the transient stability of power system. This paper focuses on the DSRs of power system with different load models, and explores the characteristic of the DSRs of the power system with constant impedance load and motor load. It deduces the algorithm for DSR of power system described with differential algebraic equation, after introducing the theory of DSR for power system with network-reduction model. And then, it presents the mathematical models for the constant impedance load and motor load. Based on the simulation results, it presents the DSRs for the power system with respect to constant impedance load and motor load, respectively. And furthermore, it compares the characteristic of the DSRs of power system with different loads, and summarizes the impact of different loads characteristic on the DSR.

关键词： power system stability power system dynamics Linear approximation Stability analysis Induction motors

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