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IEEE PES power systems Conference and Exposition, PSCE

作者： Haifeng Liang Gengyin Li Ming Zhou Chengyong Zhao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education Changping North China Electric Power University Beijing China

Focusing on the passive network, this paper analyzes the discrete mathematical model and its control strategy of the passive terminal of the VSC-HVDC system on the basis of the alpha-beta frame of axes. The method of the functioning-fuzzy-subset inference is introduced into automatic regulation of the proportional integral (PI) parameters. Based on the digital signal processor (DSP), the fuzzy PI control method is adopted and the VSC-HVDC experiment device is constructed. The experiment of constant AC voltage control based on fuzzy adaptive PI controller in transmitting power to passive network via VSC-HVDC system is developed. The experimental results show that the fuzzy controller with adaptive PI parameters for AC voltage control of VSC-HVDC system is effective.

关键词： Fuzzy control Fuzzy systems Programmable control Adaptive control control systems Voltage control Automatic control Passive networks Mathematical model Digital signal processors

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A novel method to rapidly identify inrush current and internal fault current based on variation characteristic of fundamental current amplitude

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Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2009年第6期24卷 166-171页

作者： Ma, Jing Wang, Zengping Wu, Jie Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China Zhejiang Electric Power Design Institute Hangzhou 310014 China

A new transformer protection principle based on two-instantaneous-value-product algorithm to extract the feature of fundamental current amplitude is put forward in this paper. First, the algorithm of two-instantaneous-value-product is developed, and variation trends of fundamental current amplitudes are analyzed in the case of inrush currents and internal fault currents. Whether the fundamental current amplitude reveals the descending feature or not can be used to distinguish the inrush current and the internal fault. The computational simplicity of the proposed scheme enables its implementation in real-time applications with low-cost microprocessors. dynamic testing results indicate that this method is able to clear internal fault even light fault less than a cycle and can not be affected by the current transformer saturation. Moreover, compared with the second harmonic restraint principle and the waveform comparison principle, the proposed algorithm has better performance.

关键词： Transformer protection

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Substation Reactive power and Voltage control Using Fuzzy control Theory

Substation Reactive Power and Voltage Control Using Fuzzy Co...

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International Conference on Industrial and Information systems, IIS

作者： Zengqiang Mi Fei Wang 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)9781424439362

In this paper, with analyzing the existing questions of conventional nine-area voltage and reactive power integrated control method, a new fuzzy control logic based dynamic reactive power boundary substation voltage and reactive power integrated control method is proposed. The fuzzy logic control strategies of this method can finish the decoupling control of voltage and reactive power in tight coupled zone to improve the control performance, dynamic reactive power boundary related to the system voltage can preferably adapted to the load characteristics. The system structure, fuzzy logic control rules and membership function of the proposed method are introduced. Simulation results and practical operating data have proved that this approach shows better robustness and performance compared with the conventional nine-area control method, it can reduce the adjust times of transformer tap and capacitors effectively and increase the service life of the transformer tap changer and capacitors switch.

关键词： Substations Reactive power control Voltage control Fuzzy control control systems Centralized control Fuzzy logic Fuzzy sets Switches power system stability

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Complete-independent control strategy of active and reactive power for VSC based HVDC system

Complete-independent control strategy of active and reactive...

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IEEE General Meeting power& Energy Society

作者： Chengyong Zhao Chunyi Guo 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 performance of VSC based HVDC system partially depends on its control strategy. Based on the steady state model of VSC-HVDC system, a power control strategy is proposed and a series of mathematical analysis expressions for power delivery are deduced using the coordinate conversion and variables substitution in terms of the original equations. The corresponding power controllers are designed using the PI controller and the nonlinear inverse system. Based on the strategy designed, the transmission limits of active power and reactive power are deduced. According to the circle characteristic of operation represented, it is proved theoretically that the control strategy can independently control the active and reactive power. Case studies are also carried out to testify the control strategy designed using the PSCAD/EMTDC software. Simulation results verify that the power control strategy designed can independently control active power and reactive power and the controllers have rapid responding speed, desirable stability, and highly steady state control accuracy.

关键词： control systems Reactive power control HVDC transmission Steady-state power control Nonlinear control systems Mathematical model power system modeling Mathematical analysis Nonlinear equations

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Analysis on measuring performance of three Flicker Detecting Methods

Analysis on measuring performance of three Flicker Detecting...

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IEEE General Meeting power& Energy Society

作者： Qing Chen Xiufang Jia 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

Voltage fluctuation and flicker is an important aspect of power quality. The core of flicker analysis is to track the envelope of voltage signals and then calculate the short-term flicker severity P st , which is the premise of flicker source location. This paper firstly derives the formulas of extracting flicker envelope of signals containing harmonics using Teager energy operator and Hilbert transform. Then the measuring performance of Teager energy operator, Hilbert transform and square demodulation of flicker with one frequency, multi-frequencies and with harmonics are analyzed. After extracting the flicker envelope, the flicker frequency and amplitude error, and short-term flicker severity P st error are calculated. Besides the relationships between amplitude error and frequency, P st error and frequency with respect to these three methods are illustrated respectively. At last it is proved that Hilbert transform has the highest accuracy and stability than TEO and square demodulation with the increase of frequency.

关键词： Performance analysis Voltage fluctuations Demodulation power quality Signal analysis Position measurement Energy measurement Frequency measurement Harmonic analysis Stability

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New Topological Structure of Combination Switch Based Reactive power Compensation Installation

New Topological Structure of Combination Switch Based Reacti...

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Pacific-Asia Conference on Circuits, Communications and systems, PACCS

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

A new topological structure of combination switch based reactive power compensation installation is presented in this paper. The new topological structure overcomes those shortcomings of traditional product satisfactorily by take advantage of the features of new system topological structure: concise structure, flexible configuration, high speed communication and powerful capacity of resisting disturbance. The new system topological structure and software program design features of this new installation are described in detail, contrastive analysis and practical test between the new installation and the traditional product are discussed. The results show that the new installation not only has the virtue of: structural standard, simply connection, intelligent identification, easy to extend, high reliability and high power density, but also improves the performance index by means of integrated intelligent control principle and compensation capacity dynamic modification.

关键词： Switches Reactive power ISO standards Reactive power control power system dynamics control systems Communication system control power system reliability Low voltage Access protocols

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power system real-time state estimation and prediction based on WAMS

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Dianli Xitong Zidonghua/Automation of Electric power systems 2009年第16期33卷 35-39+49页

作者： Li, Hong Li, Weiguo Bi, Tianshu Xiong, Haoqing Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China Henan Electric Power Dispatching and Communication Center Zhengzhou 450052 China

A real-time state estimator based on WAMS is presented, in which the recursive extended least-squares algorithm is used to identify the state transition matrix, and the fading memory exponential weighted algorithm is employed to estimate the error covariance matrix of the linearized model. At the same time, the measurement weights are calculated on-line by the measurement standard deviations. When the filter is done by using observed data, the imprecise (or unknown) parameters and the noise covariance matrixes of the state estimation model are constantly identified and corrected on-line simultaneously, which makes the model follow the contingencies and the time-varying process adaptively. Therefore the estimated errors are reduced, and the filtering precision is high. Simulation results show that the proposed method has good performance under different scenarios such as normal operation, bad measurements, sudden load change/drastic generation variation and topology errors. This work is supported by Program for New Century Excellent Talents in University (No. NCET-05-0216). ©2009 State Grid Electric power Research Institute Press.

关键词： State estimation

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Feedback Linearization Based Nonlinear control Strategy of VSC-HVDC

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IFAC Proceedings Volumes 2009年第9期42卷 308-313页

作者： Gengyin Li Ming Yin Ming Zhou Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing 102206 P.R. China (Tel: +86 10 80798551) State Power Economic Research Institute Beijing 100761 P.R. China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing 102206 P.R. China

The model of Voltage Source Converter (VSC) based HVDC in the synchronous dq reference frame is presented in this paper. The model includes the DC link model and the VSC models. The feedback linearization principle for Multi-input Multi-output plants is analyzed. Based on the analysis, nonlinear decoupling control strategies for the two VSCs are proposed. For one VSC, the proposed nonlinear control strategy enables it to decouple DC voltage and reactive power control, and for the other one, the strategy guarantees the control of active power and that of reactive power independently. Simulation was conducted with MATLAB/Simulink software to verify the proposed control strategies. The simulation results prove that the nonlinear decoupling control strategies are able to provide good performance.

关键词： Feedback linearization HVDC nonlinear control strategy voltage source converter (VSC)

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A novel algorithm of calculating the circulating current on the delta side of three phase wye-delta connected transformer

A novel algorithm of calculating the circulating current on ...

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IEEE/PES Transmission and Distribution Conference and Exhibition: Asia and Pacific

作者： Tao Zheng Qiang Liu Department of Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control China Electric Power University Beijing China

ISBN: (纸本)9781424452293

The circulating current on the delta side of wye-delta connected three-phase power transformer is hard to measure. The differential transformer protection has to adopt current phase compensation method to compensate the circulating current. However, the differential current hardly reflect the magnetic exciting current of transformer no matter what kind of current phase compensation methods used. It limits many algorithms of identifying inrush current, such as the promising one based on the equivalent instantaneous inductance. How to obtain the circulating currents in delta side has become a difficult problem in transformer protection. In this paper, based on the voltage equations of transformer, the calculation of the resistance and leakage inductance of winding is deduced. And then, a novel algorithm of calculating the circulating currents in delta side is proposed Simulation results of MATLAB verify the accuracy of this algorithm, which offers a new way to calculate the differential currents exactly.

关键词： power transformers Phase transformers Inductance Surge protection Equations Current measurement Asia power measurement Phase measurement MATLAB

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The finite elements analysis on magnetic field of controllable saturated reactor

The finite elements analysis on magnetic field of controllab...

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International Conference on power Electronics and Drive systems (PEDS)

作者： Wang Ziqiang Yin Zhongdong Yang Po Li Ke key Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control of Ministry of Education North China Electric Power University Beijing China Laboratory of Power System Protection and Dynamic Security Monitoring and Control of Ministry of Education North China Electric Power University Beijing China

In the power system, the controllable reactor can be used as reactive power compensation device to limit over-voltage operation, reduce no-load or light load loss and improve transmission capacity. It is with characters of simple structure, easy maintaining, low cost and high stability, etc. The magnetic field is closely related to the reactor performance. In this paper, aiming at a controllable saturated reactor prototype, using the finite elements method, the magnetic field is studied. Then, the precise 2-D prototype field-circuit coupling model is established based on the magnetic field analysis and the finite element analysis software - ANSYS. Using this model, the magnetic field and working currents concrete values under the condition that AC and DC excitations co-exist within the core are calculated. The analysis results indicate that finite element analysis theory can effectively analyze the magnetic field of the reactor.

关键词： Finite element methods Magnetic analysis Magnetic fields Inductors power system stability Software prototyping power system analysis computing Lighting control power system control control systems

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