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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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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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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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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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Effect on Earth Fault Detection Based on Energy Function Caused by Imbalance of Three-Phase Earth Capacitance in Resonant Grounded system

Effect on Earth Fault Detection Based on Energy Function Cau...

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International Conference on power system Technology (powerCON)

作者： Hongquan Ji Yihan Yang Hongbo Lian Shu'an Cong Key Laboratory of Power System Protection Dynamic Security Monitoring and Ministry of Education North China Electric Power University Beijing China School of Electrical Engineering North China Electric Power University Beijing China

In resonant grounded system when single-phase earth fault occurs, for arc suppression coil cannot compensate the active current of the zero-sequence grounding current passing through the fault point, the zero-sequence active current passing through the fault line is the sum of those passing through the non-faults. Therefore in theory the zero-sequence active current passing through the fault line is greater than others in absolute value. Energy function is the integrating of product of zero-sequence voltage with zero-sequence current. The fault line's energy function value is negative, while the non-fault's is positive. If three-phase earth capacitance is imbalanced, zero-sequence voltage produces, which will produce zero-sequence current passing through all the line. This zero-sequence current is the key variable that influences the phase-angle between non-fault zero-sequence current and the zero-sequence voltage. This paper analyzes the influences in different compensation conditions in theory. Simulation results are presented to demonstrate that the validity of earth fault line detection based on energy function will be worse and worse accompanied with the increasing of earth resistance when single-phase earth fault occurs on the imbalanced phase, and indicate that energy function has its validity scope.

关键词： Fault detection Capacitance Resonance Voltage Earth power system security Coils Electrical fault detection Laboratories power system protection

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Application of controllable Reactor in Suppressing the Voltage Fluctuation and Flicker under Hα control Strategy

Application of Controllable Reactor in Suppressing the Volta...

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International Conference on power system Technology (powerCON)

作者： L.x. Zhou Z.d. Yin J.r. Lin F.x. Hu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China postgraduate student School of Electrical Engineering North China Electric Power University Power Dispatching and Communication Center China Southern Grid.

Voltage fluctuation and flicker are mainly caused by surge load with large capacity, which may lead to the unstable operation of the motor, the poor characteristics of electrical equipments and the mis-operation of the electronic device even damage etc. Traditional SVC can adjust the reactive power ideally to maintain the system voltage of the connection point and play an excellent role in suppressing the voltage fluctuation and flicker. The minor defect is that it can not be directly applied to the ultrahigh or extra-high voltage system. This paper puts forward a topology of SVC based on the controllable reactor. It can be made into voltage at any level to connect to the ultra-high or extra-high voltage network directly, and can dynamically adjust the saturation degree of the controllable reactor according to the fluctuation of the reactive power of the system, smoothly change the reactive power it sends out, effectively suppress the voltage fluctuation and flicker. Meanwhile, H alpha control is taker as the main control strategy. The validity of proposed approach is verified by calculation and simulation.

关键词： Voltage fluctuations Voltage control Inductors control systems Lamps Automatic voltage control Static VAr compensators Reactive power control power system control power systems

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The Study of Detailed Fossil Fuel Steam Unit Model for Long-term power system dynamic Simulation

The Study of Detailed Fossil Fuel Steam Unit Model for Long-...

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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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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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Study on Xiluodu and Xiangjiaba UHVDC Earth Electrodes

Study on Xiluodu and Xiangjiaba UHVDC Earth Electrodes

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International Conference on power system Technology (powerCON)

作者： Mingde Cui Lianguang Liu Zhongming Sun Key Laboratory of Power System Protection andDynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China Beijing Wanglian HVDC Engineering Technology Company Limited Beijing China

Grounding characteristics of linear, star-type and toroidal electrodes are discussed in this paper. Based on the analysis of the performance of double-ring in uniform and horizontal two-layer soils, an electrode model of standard triple concentric rings buried with different depth is presented for plusmn800 kV Xiluodu and Xiangjiaba converter stations in the first period of Jinsha River DC projects. Considering the three sending converter stations in the projects close to each other relatively, an initial analysis of sharing electrodes has been made, including the operation mode of converter stations, choice of rated current and the design model of electrodes. Simulation results obtained from the electrode sites primarily selected for Xiluodu right-bank converter station show that the above model can satisfy the operation requirements with a better economical performance and sharing electrodes by multi-converter stations is also feasible. They may supply some reference to the practical projects.

关键词： Earth Electrodes Grounding Rivers Soil control systems Sun Hydroelectric power generation Geology Performance analysis

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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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