Vscf Doubly Fed Wind Power System Excitation Control Study

Energy and environment are the urgent problems that human beings exist and development nowadays.Wind power has attacted more and more highly attention as one kind of clean regenerative energy sources. With the wind generator capacity increasing, How to improve th operation efficiency and maximum use the wind power has become a hotspot. More and more doubly-fed induction generator (DFIG) of wind power system has been used, the research on its control strategy and how to further improve the system stability and dynamic operation ability has a vital significance.Consider of the excellent static and dynamic performance, high-quality precision of control, matrue for industrial areas. But it has some weakness like that it must need repeated coordinate transformation and the control system has complicated structure.Direct Powe Control (DPC) strategy is based on in direct torque control (DTC), It's characteristic is that the simple structure, fast dynamic response and robust performance of the parameters is good. But it's has some obvious weakness in traditional DPC strategy,such as the switch frequency not constant, output current has a little harmonics, the fluctuation of direct voltage and active power and reactive power when the system strats., control accuracy is not high.The paper puts forward two improved strategies aimed at the characteristics of the DPC strategy:DPC strategy based on fuzzy PI controller and DPC strategy based on Space Vector Modulation (SVM). A fuzzy PI controller is proposed and successfully applied in DPC strategy which is the core content of the DPC strategy based on fuzzy PI controller. Simulation results show that the strategy could effectively reduce the fluctuation of the direct volage,active power and reactive power when the system strats. DPC strategy based on SVM introduced SVM in traditional DPC strategy and proposed a new construction method of voltage space vector which aimed at the DPC strategy weakness that output current has a little harmonics, reactive power out of control in small areas. Simulation results show that the strategy could make the switching frequency constant, effectively reduce the area of reactive power out of control and reduce the output current harmonics.