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Sensitivity analysis for AC/DC hybrid power systems

Dianli Xitong Zidonghua/Automation of Electric power systems 2007年第12期31卷 45-49页

作者： Liu, Chongru Zhang, Boming Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China State Key Lab. of Power Systems Department of Electrical Engineering Tsinghua University Beijing 100084 China

The interactions between AC and DC systems in the steady-state condition of power systems are investigated. Through a sensitivity analysis, the influence of DC control parameters on the operation of AC/DC systems and that of AC control parameters on other AC parameters with the DC system existing are discussed. The sensitivity matrices and the influence factors between AC and DC systems are analyzed from various points of view. The sensitivity analysis made in this paper is expected to be of practical significance in such problems as load flow control, parameter regulation, voltage estimation, etc.

关键词： Electric power transmission networks

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The propagation characteristics of electromagnetic wave generated from partial discharges in power transformer by FDTD simulation

The propagation characteristics of electromagnetic wave gene...

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2007 Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP

作者： Tang, Zhiguo Li, Chengrong Wang, Wei Wang, Hui Wang, Li Ding, Yansheng Beijing Key Laboratory of High Voltage and EMC Ministry of Education North China Electric Power University Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University State Grid Corporation of China 100081 Beijing China Beijing Key Laboratory of High Voltage and EMC School of Electric and Electronic Engineering North China Electric Power University P.O. No.88 Beijing 102206 China

The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM *** results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path. ©2007 IEEE.

关键词： Electromagnetic waves

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Reallocating-damping theory of PSS and HVDC modulation

Reallocating-damping theory of PSS and HVDC modulation

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2007 International power Engineering Conference (IPEC2007), vol.2

作者： Shanshan Zhao Li Lin Xiangyu Tao Yonghua Yin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control and China Electric Power Research Institute North China Electric Power University China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China China Electrical Power Research Institute China

In an AC/DC large-scale interconnection power grid, there are many problems to be solved. Among these, small-signal stability is extremely important. In this paper, based on the reallocating -damping theory of PSS, reallocating-damping theory of HVDC modulation is proposed, that variation of gain of HVDC modulation doesn't influence the system general damping. It is also proved that reallocating-damping theory unifies PSS and HVDC modulation, which are both damping control measures. Mathematics deduction is given in detail. The possible negative effect caused by PSS and HVDC modulation is analyzed. A number of cases are tested such as a 12-generator system, 2DC system and a real power system.

关键词： Low frequency oscillation PSS HVDC modulation Reallocating-damping theory AC/DC hybrid grid Damping characteristics

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Modeling of the Wind Turbine with a Permanent Magnet Synchronous Generator for Integration

Modeling of the Wind Turbine with a Permanent Magnet Synchro...

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IEEE General Meeting power& Energy Society

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

The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbine model and a drive train model. The drive train model uses one-mass model to represent the mechanical characteristics of the generator set. The generator model is established in the dq-synchronous rotating reference frame. The wind turbine model details the mechanism of variable speed operation of the turbine by a pitch control. The control schemes in the paper include a pitch angle control for the wind turbine and a speed control for the generator. The pitch angle control uses wind speeds and electric power output as the input signals to ensure normal operation in high wind speed. The speed control is realized through field orientation where the d-axis current is set to zero and the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed. In order to verify the presented model and the control strategy, simulations with MATLAB/Simulink software have been conducted. Simulation results prove the validity of the model and the control schemes.

关键词： Wind turbines Permanent magnets Synchronous generators Mathematical model Mechanical variables control Electric variables control Wind speed Magnetic variables control Velocity control Wind energy generation

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Research on energy efficiency of supercapacitor energy storage system

Research on energy efficiency of supercapacitor energy stora...

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2006 International Conference on power system Technology, powerCON2006

作者： Yun, Zhong Jiancheng, Zhang Gengyin, Li Aiguo, Liu Department of Electrical Power Engineering North China Electric Power University Baoding. Hebei 071003 China School of Information Engineering Nanchang University Nanchang Jiangxi 330029 China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China

ISBN: (纸本)1424401119

Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices which are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power. Equivalent serial resistance is put forward to estimate energy efficiency. Reducing the equivalent series resistance in a supercapacitor will gain a great appreciation. A supercapacitor energy storage system (SCESS) is also designed in this paper which is mainly composed of three parts: the electrical double-layer capacitors array that stores energy, the AC/DC-DC/AC power converter system and the integrated control system composed of microprocessors. This SCESS installed capacity is 0.235MJ;peak power is 5OkW;and generating efficiency is up to 97.94%. © 2006 IEEE.

关键词： Energy efficiency

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Decoupling Control for Multiterminal VSC-HVDC Based Wind Farm Interconnection

Decoupling Control for Multiterminal VSC-HVDC Based Wind Far...

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IEEE General Meeting power& Energy Society

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

In the paper multiterminal voltage source converter based HVDC (VSC-HVDC) is proposed to interconnect wind farms to AC grids. The method highlights the control at the level of wind generator cluster that comprises several permanent magnet synchronous generators without the primary converters on themselves. For the cluster control, active and reactive power decoupling scheme is applied to adjust the rotational speed of the cluster according to wind speed. The paper studies the schemes to control grid side converter based on the philosophy of linear decoupling control, which aims to control the DC voltage as well as the reactive power of VSC-HVDC. In the proposed control scheme, the two goals are achieved by controlling the q- and rf-axis components of the grid's fundamental current. Simulation has been performed using engineering software Matlab/Simulink to verify the interconnection method and validate the control scheme as well.

关键词： Wind farms Converters power conversion Voltage control Synchronous generators Reactive power control HVDC transmission Wind energy generation Permanent magnets Wind speed

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Multi-layer Disturbance Processing system based on Multiple Information Sources

Multi-layer Disturbance Processing System based on Multiple ...

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IEEE General Meeting power& Energy Society

作者： Tianshu Bi Qian Li Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

More and more IEDs have been commissioned in power systems, such as digital relays, PMUs, metering and control devices, fault recorders and so on. Once there is a disturbance (for example, fault, low-frequency oscillation, etc.), large amount of information will pour into the control center. Therefore, how to identify the disturbance and then take corresponding countermeasures is crucial for power system security and reliability. A multi-layer disturbance processing system based on multiple information sources is proposed in this paper. Firstly, the characteristics of different kinds of information sources, including PMUs, RTUs, digital relays and fault recorders, are analyzed. Secondly, according to the arrival times of the information, the framework and functions of multi-layer fault diagnosis system is presented in detail. After a disturbance occurs, the suggested system could realize disturbance identification, fault element diagnosis and detailed post-fault analysis in succession at different time frames with the information coming, which fits the needs of operators well.

关键词： Fault diagnosis Digital relays Phasor measurement units power system reliability Information analysis power system faults power system relaying power system control power systems Control systems

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Research on identifiability of equivalent motor in composite load model

Research on identifiability of equivalent motor in composite...

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2007 IEEE Lausanne powerTECH

作者： Ma, Jin Han, Dong He, Renmu Dong, Zhaoyang Hill, David J. IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University 102206 Beijing China School of Information Technology and the Electrical Engineering University of Queensland St. Lucia QLD 4072 Australia Department of Information Engineering Australian National University

ISBN: (纸本)9781424421909

Load modeling is very important for power system dynamic analysis and control. The composite load model widely applied recently in the power system operation centre consists of the static load and the equivalent motor. Current practices in measurement-based load modeling identify all the parameters in this composite load model. However, it is not clear whether all these parameters could be identified from the measurements. This paper investigates the identifiability of the equivalent motor parameters in the composite load model. Trajectory sensitivity approach is applied first to find the motor parameters that have great effects on the measured active as well as reactive load dynamics. The analysis results show that the motor outputs have various sensitivities with respect to the parameters. Since the voltage disturbance, the active load and the reactive load dynamics are applied to identify the motor parameters, those parameters affecting the measurements to a great extent are observable, thus identifiable from the measurements;while those that have little effects on the motor outputs are unobservable from the measurements and consequently unidentifiable. The case studies verify the identifiability of the motor parameters. ©2007 IEEE.

关键词： Parameter estimation

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Research on PT Ferromagnetic Resonance Region and the Controllable Damping

Research on PT Ferromagnetic Resonance Region and the Contro...

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power Tech Conference

作者： L. X. Zhou Z. D. Yin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

In the neutral ungrounded system, potential transformer (PT) ferro-magnetic resonance is a kind of interior overvoltage which is frequently appears and creates most of the accidents. Whether the elimination measures are reasonable and effective or not affects the security and stability of the power system directly. Fundamental research has been done on the resonance region changeable situation and the characteristics of each resonance region under different system parameter and PT saturation characteristics. According to the occurring principle of PT ferromagnetic resonance and the characteristics, a novel effective controllable damping device is designed, which will change the correlative parameter that lead to resonance to make the circuit parameter of the system get out of the resonance area to eliminate the resonance. The accuracy of the fundamental analysis and the effectiveness of the elimination measure have been verified by the digital simulation based on EMTDC/PSCAD and by the high voltage propotype experiment.

关键词： Magnetic resonance Damping power system security power system stability PSCAD Voltage transformers Voltage control Accidents power measurement power system measurements

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Phase-to-Phase Distance Relay Based on the Measured Impedance Trajectory

Phase-to-Phase Distance Relay Based on the Measured Impedanc...

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IEEE General Meeting power& Energy Society

作者： Huanzhang Liu Qiankuan Liu Shaofeng Huang Qixun Yang Huazhong Electric Power Dispatch and Communication Center Wuhan China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

The measured impedance trajectory changing with fault resistance during multi-phase faults and the reasons that fault resistance may cause unwanted impedance relay operations in two-source systems were analyzed in this paper. To improve the impedance relay adaptive ability and reliability during three phase fault, a combined phase-to-phase impedance relay based on the measured impedance trajectory was presented. The relay is composed of three criteria respectively called the reactance line based on the measured impedance trajectory, the sending end and the receiving end directional lines, whose transient and steady state operating characteristics have been analyzed for forward and reverse faults. The simulation test was made by RTDS on a 340 km long 750 kV line in a two-source system. Theoretical analysis and dynamic simulation test results show that the adaptive relay can respond to three phase faults and phase-to-phase faults, and has satisfactory performances.

关键词： Protective relaying Impedance measurement Phase measurement Relays Electrical resistance measurement Transient analysis Steady-state system testing Performance analysis Analytical models

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