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International Conference on power system Technology (powerCON)

作者： Peng Li Wei Wang Xilei Yang Shuai Wang Hongfen Cui Changzheng Gao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China Jilin Electric Power Company Limited Changchun Jilin China

Microgrid, as a new effective way for large scale new energy and renewable energy power generation systems connected to the grid, injects new vigor into the power system. Focusing on the characteristics of P-f (active power versus frequency) droop and Q-V (reactive power versus voltage) droop, on the basis of analyzing the variable slope coefficient of droop characteristic, a droop control method of microsources based on divided self-adjusting slope coefficient is proposed in this paper. By calculating the quantity of the load fluctuation, this control method dynamically adjusts the active and reactive power maximums of inverters in the range of the inverter ratings to change the slope coefficients of droop curves. The aim of this method is to decrease the deviation of the frequency and voltage magnitude of the microgrid bus effectively. The simulation result verifies the correctness and feasibility of this control method.

关键词： Reactive power Inverters Fluctuations Voltage control Artificial neural networks

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A transformer fault diagnosis method integrating improved genetic algorithm with least square support vector machine

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Dianwang Jishu/power system Technology 2010年第2期34卷 164-168页

作者： Zhang, Kai Huang, Hua-Ping Yang, Hai-Tao Xie, Qing Shijiazhuang Power Supply Corporation Shijiazhuang 050000 Hebei Province China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Ministry of Education Baoding 071003 Hebei Province China Communication and Dispatching Center of Guang'an Electric Power Bureau Guang'an 638000 Sichuan Province China

Least square support vector machines (LS-SVM) can solve small sample nonlinear multi-classification problem well, so it is applicable to the power transformer fault diagnosis by dissolved gas analysis (DGA), however the selection of parameters c and σ2 greatly impacts the diagnosis result, thus the optimized selection of these parameters is necessary. In this paper, the improved genetic algorithm (IGA) is applied to the optimized selection of c and σ2. The initial population of IGA is randomly generated by coding mechanism, in this way, the search space can be quickly expanded and the diversity of individuals in the populations can be stabilized, thus both global search ability and convergence speed can be effectively improved. The LS-SVM optimized by IGA is applied to fault diagnosis by multi-sets of chromatographic data of transformer oil and the result shows that optimizing LS-SVM by IGA, the optimized selection of c and σ2 can be implemented effectively and the accuracy of power transformer fault diagnosis can be improved.

关键词： Failure analysis

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Modeling and simulation of a microturbine generation system based on PSCAD/EMTDC

Modeling and simulation of a microturbine generation system ...

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International Conference on Critical Infrastructures, CRIS

作者： Gang Li Gengyin Li Wei Yue Ming Zhou K L Lo Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow UK

Distributed generation (DG) technology has drawn increasing attention for its tremendous benefits to customers, utilities and the environment. Furthermore, microturbine based power generation has become the most promising DG for its excellent record of improving system stability and economy. In this paper we develop a complete mathematic model, which includes the microturbine, a permanent magnet synchronous generator (PMSG), a three-phase bridge AC to DC rectifier, a boost converter and a DC to AC inverter. The simulated microturbine generation system (MTGS) model is a single shaft type with control systems and capable of regulating its output power in grid-connected mode. Also, the design and modeling of a MTGS which is suitable for isolated operation are explained with the ability of electronic controls that maintains the output voltage at their prescribed levels. Different load conditions are applied to the MTGS for evaluation of the validity and practicability of the model. Simulation studies have been carried out in PSCAD/EMTDC under different load conditions. Simulation results testify that the MTGS developed from this model can produce predictable results with these control methods.

关键词： Fuels Mathematical model Load modeling Inverters power generation Voltage control Torque

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The generating mechanism and optimal control of power quality in micro-grids

The generating mechanism and optimal control of power qualit...

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International Conference on power system Technology (powerCON)

作者： Xi Li Zhongqiu Wang Gengyin Li Ming Zhou K L Lo Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow UK

As an important component of distribution network, micro-grid is the necessarily development trend for future. Micro-grid has greatly improved the random problems of distributed generation (DG). However, DGs, the power electronic equipments inevitably bring about power quality problems, especially voltage flicker and harmonics. This paper tries to study the operating regulations of micro-grid in order to find out the generating mechanism and propagation characteristic of power quality problems. Taking the photovoltaic (PV) system for an example, the micro-grid simulation model has been set up. The experiments show that an appropriate control strategy coordinating every part can improve the power quality of micro-grid greatly. This paper finds out the factors affecting power quality and their harm degrees, explaining the reasons of power quality problems. Coordinating every unit, this paper set up an optimal control strategy and proper parameter settings, trying to improve power quality of micro-grid to the largest extent.

关键词： power quality Biological system modeling Inverters Harmonic analysis power grids Integrated circuit modeling Voltage fluctuations

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Research on the Voltage Source Converter in VSC-HVDC

Research on the Voltage Source Converter in VSC-HVDC

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International Conference on power system Technology (powerCON)

作者： Jingmei Fang Gengyin Li Ming Zhou Xuefeng Liang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Controlunder Ministry of Education North China Electric Power University Beijing China School of Electrical and Electronic Engineering North China Electric Power University Beijing China

Voltage Source Converter (VSC) based High Voltage Direct Current (VSC-HVDC) transmission technology is a novel transmission technology on the basis of pulse width modulation (PWM) technology and fully-controlled power electronics devices. The output performance of VSC mainly depends on its modulation algorithm. A new kind of SVPWM algorithm based on 60° coordinate system for three-level VSC is introduced in this paper, and the neutral-point voltage imbalance problem is effectively solved by introducing an adjusting coefficient. And the high output voltage rating demand of VSC in VSC-HVDC can be achieved by connecting insulated gate bipolar transistors (IGBTs) in series. In order to solve the static and dynamic voltage unbalance problem associated with series-connected IGBTs, a new method combining with voltage clamp circuits and gate passive voltage balancing circuits is presented in this paper, and the effectiveness of the circuit is validated by simulation results.

关键词： Insulated gate bipolar transistors Switches power conversion Capacitors Space vector pulse width modulation

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An improved grey model for forecasting spot and long term electricity price

An improved grey model for forecasting spot and long term el...

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International Conference on power system Technology (powerCON)

作者： Zheng Yanan Gengyin Li Ming Zhou Shan Lin K L Lo Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow UK

With the deepening reform to power industries, power systems are going to gradually open the demand side and the power consumers have to face the changes of their role in the market, and make a preliminary long-term forecasting for the electricity prices. In order to consider the relations between the spot market and the long-term contract market, this paper builds a multi-electricity price grey model to comprehensive forecast the prices of the 2 markets; further researches the structure of the background value, and improves the multi-electricity price grey model; and introduces the residual error, the related grade, the mean variance ratio and the little probability of error as test indexes. The test results show that the multi-electricity price grey forecasting model and its improved model have better accuracy, and the improved model has stronger adaptability and extends the application range.

关键词： Forecasting Contracts Predictive models Electricity Accuracy Fitting Indexes

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Synthetic evaluation of power quality based on entropy of relative intensity and local variable weight

Synthetic evaluation of power quality based on entropy of re...

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International Conference on power system Technology (powerCON)

作者： Guodong Li Gengyin Li Xueqian Fu Ming Zhou Key Laboratory of Power System Protection and Dynamic Security Monitoring and Controlunder Ministry of Education North China Electric Power University Beijing China School of Electrical and Electronic Engineering North China Electric Power University Beijing China

A new method of power quality synthetic evaluation based on relative intensity entropy and local variable weight is presented in the paper. This method firstly uses the relative intensity entropy theory to extract the weights of the individual power quality indicators, and then does synthetic evaluation to the power quality data combined with the method of local state variable weight to amend the index weights, and gives the assessment point levels of their power quality. This new evaluation method embodies the gradual change of objective evaluation index weights with indicators values, and could do incentives and penalties to some weights of internal indicators. The simulation results show that the method proposed in this paper is more suitable for power quality evaluation, and has more practical significance.

关键词： Entropy Voltage fluctuations

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Integration of protection and control systems for smart substation

Integration of protection and control systems for smart subs...

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International Conference on Critical Infrastructures, CRIS

作者： Jing Ma Tong Wang Jie Wu Zengping Wang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China State Nuclear Electric Power Planning Design and Research Institute Beijing China

Digital based data processing and protection and control system along with digital communication networks introduces new structures for substation protection and control systems and new methods for intelligent protection and control systems. This paper presents a unique vision for the future integration of protection and control systems. Firstly, the basic concept and configuration of the developed protection and control systems for smart substation is introduced. The features and functions of integrated protection and control systems for smart substation are then discussed and compared with that of the traditional substation in detail.

关键词： Substations Control systems Local area networks Artificial intelligence Monitoring power system reliability

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Energy storage control for the Photovoltaic generation system in a micro-grid

Energy storage control for the Photovoltaic generation syste...

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International Conference on Critical Infrastructures, CRIS

作者： Zhongqiu Wang Xi Li Gengyin Li Ming Zhou K L Lo Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow UK

Distributed generation (DG) that uses renewable energy sources has an unstable output and this can negatively affect existing electric power systems. In order to reduce above impact, we need to develop an energy control system to control the output through individual DG installed in a micro-grid. First, this paper designs a grid-connected Photovoltaic (PV) system and introduces the operation principle of the various parts as well with the control strategy of the power flow. The design of energy storage is of great significance as the output power of PV cells array is greatly affected by the light intensity and the temperature change. Then, it uses the battery as the energy storage device and designs the charge-discharge control strategy according to the characteristics of the battery. Finally it verifies the feasibility of the energy storage control strategy through the simulation models which is built based on the PSCAD/EMTDC platform.

关键词： Batteries Discharges Voltage control Arrays Solar power generation

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Multi-agent approach for service restoration of microgrid

Multi-agent approach for service restoration of microgrid

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IEEE Conference on Industrial Electronics and Applications (ICIEA)

作者： Peng Li Bin Song Wei Wang Tiemin 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 Baoding Tianwei Wind Power Blade Company Limited Baoding Hebei China

Considering the operation of microgrids (MGs) composed of distributed generations (DGs) and loads, a service restoration model aiming at the restoration of the most load with giving priority to the important load power supply is built. On the basis of the proposed hierarchical control strategy, this paper builds up a multi-agent system (MAS) for service restoration of microgrid. Accordingly, the special functions and control strategies of each agent are discussed in detail. A simulation example of a particular microgrid based on the multi-agent system is performed to demonstrate that the efficiency and reliability of the microgrid can be improved by using MAS.

关键词： power system restoration Multiagent systems Distributed control Control systems Cogeneration power system modeling power system reliability Artificial intelligence Communication system control Switches

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