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International Conference on power system Technology (powerCON)

作者： Xianrong Chang Zhenjian Guan Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education(North China Electric Power University) Baoding Hebei P.R.China School of Electrical Engineering North China Electric Power University Baoding Hebei P.R.China

Long-term power system dynamic simulation needs to reflect the dynamic process of the fossil fuel steam unit when occurring severely disturbances in the power system. A physically based detailed model of the fossil fuel steam unit for power system long-term dynamic simulation has been described in this paper. The model can reflect the dynamic variation of the internal parameters accurately. In particular, the detailed model considers the dynamic impact on the turbine output from the extraction system. The simulation is much closer to the reality in the power system long-term dynamic process. This detailed model of the fossil fuel steam unit can be used for the power system long-term dynamic simulation.

关键词： Fossil fuels power system modeling power system dynamics power system simulation Turbines power generation power system stability power system transients power system analysis computing Furnaces

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The Perturbed Trajectories Prediction Method Based on Wide-Area Measurement system

The Perturbed Trajectories Prediction Method Based on Wide-A...

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IEEE PES Transmission and Distribution Conference and Exposition

作者： Song Bi Li Yang Liu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China North China Electric Power University Beijing Beijing CN Beijing Power Company in Beijing China

In this paper, a novel method for perturbed trajectory prediction of post-fault rotor angle is presented based on PMU (phasor measurement unit) measurements and trigonometric function curve fitting technique. A mathematical model about the relationship of post-fault rotor angle and time is derived from a speed-governing system model, which reveals that the perturbed trajectory of the post-fault rotor angle can be expressed by trigonometric functions. By curve fitting technique, a least square method to predict the perturbed trajectory using trigonometric function is proposed. Numerical simulations are conducted on IEEE 9-bus system to test the effectiveness of this method. The proposed method can give more reasonable and more promising prediction results as compared with polynomial curve fitting technique

关键词： Trajectory Prediction methods Wide area measurements Curve fitting Phasor measurement units Mathematical model Measurement units Least squares methods Numerical simulation system testing

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Application of Wavelet Entropy and Adaptive Nerve-fuzzy Inference to Fault Classification

Application of Wavelet Entropy and Adaptive Nerve-fuzzy Infe...

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International Conference on power system Technology (powerCON)

作者： Bin Zhang Zhengyou He Qingquan Qian Lanzhou Jiaotong University Lanzhou Gansu China Southwest Jiaotong University Chengdu Sichuan China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University China

A new method of fault classification based on transient signals for high voltage power transmission line is presented. Based on the wavelet analysis and the idea of entropy, the concept and definition of wavelet energy entropy (WEE) for feature extraction are introduced. First, appropriate wavelet decomposition of acquired post-fault signal is conducted and the WEE is calculated. ; then the characteristic vectors for post-fault signal are built; the characteristic vectors containing fault information are used as the input of adaptive nerve-fuzzy inference system; finally, the fault classification is realized according to the output of adaptive nerve-fuzzy inference system. The simulation results of fault classification have been analyzed on a 500 kV transmission line PSCAD/EMTDC model. The result shows that the variation regularity of WEE with time can effectively reflect fault features. With the help of adaptive nerve- fuzzy inference system, it achieves good classification effect.

关键词： Entropy power transmission lines Wavelet analysis Adaptive systems power system transients Voltage Feature extraction Analytical models PSCAD EMTDC

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Analysis of ionized field under /spl plusmn/800 kV HVDC transmission lines

Analysis of ionized field under /spl plusmn/800 kV HVDC tran...

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International Zurich Symposium on Electromagnetic Compatibility (EMC Zurich)

作者： Tiebing Lu Jie Zhao Xiang Cui Han Feng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control underMinistry of Education North China Electric Power University Baoding Hebei China Technology research center China Southern Power Grid Company Limited Guangzhou Guangdong China

HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method to analyze the ionized field generated from the bundled conductors of bipolar lines is proposed. And then, after the validity of the method is testified, some examples are analyzed and some conclusions are drawn finally. The results have been used in the design of plusmn800 kV HVDC transmission lines system in China

关键词： HVDC transmission Space charge Corona Conductors Equations power transmission lines Electromagnetic field theory Testing power generation Voltage

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Novel scheme to fast discriminate inrush current from internal fault of power transformer

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第2期26卷 47-51页

作者： Lu, Zhi-Juan Liu, Wan-Shun Xiao, Shi-Wu Zheng, Tao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

A new algorithm based on waveform characteristics is presented for fast discrimination between inrush current and fault current of power transformers. The method is based on that the waveform of inrush current (concave) distorts seriously, while the fault current nearly keeps sinusoid (convexity). Utilizing the sample data within 5 ms after fault initiation and extending the data windows from 5 ms to 10 ms, the approximate current formula can be extracted from fault current or inrush current using least square fitting method. According to the curvature and convex-concave characteristic of the fitting curve, inrush current and fault current of power transformers can be distinguished. Experimental results indicate that this algorithm is not only effective under various fault conditions but also can be realized easily and hardly to be affected by current transformer saturation and decaying DC components. Moreover, fault clearance time can be limited within 5 ms.

关键词： Electric transformers

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New acquiring path of power system dynamic parameter based on RBFNN recognition

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第10期26卷 104-108页

作者： Zhao, Shu-Tao Li, Bao-Shu Yuan, Jin-Sha Zhao, Dong-Sheng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

Acquiring the dynamic parameters based on computer vision instead of manual patrol, and via comparing power meter reading with its preliminary definition threshold, which is a new automatic monitoring scheme of power system running. In the process of power meter automatic recognition, three particle feature invariants, include length ratio, compactness and simplicity factor have been extracted. The RBFNN is utilized in the dial plate elements recognition. The meter identifying experiments proved that the RBFNN input invariants are stable and proper, and it is insensitive to the background noise. It can optimize the power system monitoring with the image-analyzing introducing.

关键词： Electric power systems

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Study on cascaded SSSC small-step ( less than or equal 2 μs) modeling in RTDS

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Gaodianya Jishu/High Voltage Engineering 2006年第10期32卷 72-75+90页

作者： Jiang, Xu Xiao, Xiangning Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Static Synchronous Series Compensator (SSSC) is a sort of FACTS equipments based on the series Voltage Source Converter (VSC). The small-step ( less than or equal 2 μs) model of SSSC is built in RTDS in this paper. The main circuit structure of SSSC consists of cascaded H-bridge units and single-phase coupling transformer. Because of the simple and independent connection among three phases, it is easy to present the unbalanced compensation. The modulation strategy of SSSC which adopts staircase modulation can be got on-line;it uses equal area principle to calculate the trigger angels in this way. Constant impedance strategy is also applied, namely the output voltage of SSSC is proportional to the line current in amplitude and leads or lags the line current by π/2. Details for building cascaded multilevel SSSC model in RTDS are shown in this paper;in addition, there are also some tips about how to present the small-step simulation of VSC. Firstly, the VSC module must be arranged suitably on the allowable simulation scale. Secondly, the special transformer has to be used at the interface between large step model and small step one. Thirdly, in order to avoid the 'stiff' instance of the interface, the VSC breaker must substitute for the large step side breaker. Finally, the division module must be set properly in that the dividend may equal to zero. Moreover, the results including indices such as P, Q, current of line, modulation index and output voltage under different running conditions have proved that the model in RTDS is almost perfect by comparing with the results got in EMTDC/PSCAD4.02.

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Research on Restraining Low Frequency Oscillation with Flywheel Energy Storage system

Research on Restraining Low Frequency Oscillation with Flywh...

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International Conference on power system Technology (powerCON)

作者： Yun Zhong Jiancheng Zhang Gengyin Li Zhiyuan Chen School of Information Engineering University of Nanchang Baoding Jiangxi China Department of Electrical power Engineering North China Electric Power University Baoding Hebei China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China Baoding Zhongli Power Science and Technology Development Company Limited Baoding Hebei China

Low frequency oscillations in the interconnected power systems are observed all around the world. Besides conventional PSS to suppress Low frequency oscillation, there are other modern FACTS devices to damp oscillation, among which flywheel energy storage system (FESS) is a comparative valid way. The theory on restraining low frequency oscillation used by flywheel energy storage system is described through transfer function diagram and complex torque coefficient. A numerical model of flywheel energy storage asynchronous motor controlled by VVVF inverter is derived from its mathematical model in alpha-beta coordinate system. Then the total model eigenvalue is analyzed. Based on analysis, attach control strategy using two parallel independent parts for active power control and reactive power control is designed in FESS to restrain low frequency oscillation. The calculation result shows that flywheel energy storage system is an effective way to restrain low frequency oscillation and enhance power system dynamic performance.

关键词： Frequency Flywheels Energy storage power system interconnection Transfer functions Torque Numerical models Inverters Mathematical model power system modeling

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power system Transient Stability Simulation Using the Precise Time-Integration Method

Power System Transient Stability Simulation Using the Precis...

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International Conference on power system Technology (powerCON)

作者： Xianrong Chang Yubin Wang Lifeng Hu School of Electrical Engineering North China Electric Power University Baoding Hebei China Power Supply Bureau of Shijiazhong Hebei China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education(North China Electric Power University) and School of Electrical Engineering North China Electric Power University Baoding 071003 Hebei Province P. R. China. e-mail: HLF873@***

Based on the precise time-integration method and the models of power system, a fast and simple simulation method for power system transient stability is discussed in this paper. This method has its advantages such as the numerical stability and programming simplicity. The techniques of factorization and sparse matrix are used in this method. The computer simulations on a real-life system prove the effectiveness of this method.

关键词： power system transients power system stability power system simulation power system modeling power system reliability Numerical stability power system protection power system dynamics power system security power system analysis computing

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Researches on high order harmonics interference and filters at DC side of UHVDC transmission system

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Gaodianya Jishu/High Voltage Engineering 2006年第12期32卷 174-177页

作者： Zheng, Jin Wen, Jun Shi, Yan Han, Minxiao Yan, Jinchun Beijing Wanglian HVDC Engineering Technology Co. Ltd. Beijing 100088 China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

The communication of power line carrier (PLC) in the frequency of 20-500 kHz in the ultra-high voltage direct current (UHVDC) transmission line with ±800 V rated voltage and the radio communication range from 500 kHz-20 MHz near the converter substation and along the ultra-high voltage direct current transmission line are interfered strongly by high order harmonics from converters and direct current transmission line and neutral line of ultra-high voltage direct current transmission system. It's a virtual way to reduce power line carrier interference (PLCI) and radio interference (RI) to install PLC/RI filters at the terminals of the polar line and neutral line at the direct current side of converter substation. The power line carrier interference and radio interference from the ultrahigh voltage direct current transmission system with two series of 12 pulse converters in a pole line are produced by the chopping of valve voltage of converters and the discharging of electric corona and insulators. The limitation values for power line carrier interference and radio interference from the converter substation of ultra-high voltage direct current transmission system are analyzed in the paper. After calculating the total power line carrier interference and radio interference at the terminal of the direct current pole line and neutral line in the circumstance of PLC/RI filter schemes with a harmonic analysis program, a economical and practical PLC/RI filter scheme for limiting power line carrier interference and radio interference at the direct current side of ultra-high voltage direct current converter substation is produced.

关键词： Communication Filters Harmonics power Line Carrier (PLC) Radio Interference (RI) UHVDC transmission

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