Study On Control Of Low Voltage Ride Through Of Double-Fed Wind Power Generation System

With the development of the world’s economy, the requirement of the energy becomes much more vastly. Because of the clean and inexhaustible characteristics, the wind attracts people’s attitude and the technology of wind power generation is improving. But with the installed capacity of wind power generator becomes much more large, the more effect on power grid. The wind power generator out of work regularly is a challenge to the reliability of power supply. Some researches show that the main reason for the equipment failure is that the ability of the generator’s low voltage ride through that can’t satisfy the requirement. So it’s necessary to study the ability of the generator’s low voltage ride through.With its own advantage, the double-fed wind power generator system has become the main trend among the existing wind power generator system. In this paper, we start our research with the Double-fed wind power generator as our main object. The paper introduces the basic structure and the principle of the Double-fed wind power generator, then we construct the mathematic model and simulate in MATLAB platform. After that, the LVRT is studied under the condition of grid voltage sagging. We know that the improved control can have an effect on the voltage of small amplitude drop by researching, otherwise crowbar circuit is needed to improve the LVRT ability. The main research contents are as follows.Firstly, constructing the mathematic model by the principle of wind turbine, the Double-fed wind power generator and converter, simulation follows.Secondly,the wind turbine control methods are studied with different control strategies according to the wind turbine under different operation conditions, the control method of maximum wind energy capture is used by a low wind speed and constant power control comes out with the wind speed over the rated value.In addition, the three-phase AC of rotor excitation converter between the grid and rotor is designed,and the parameter of PI regulator is set according to the engineering design method.Based on the simulation on the MATLAB/Simulink, this paper makes a research about influence on the doubly-fed wind power generation system when a failure happened caused by the voltage fall down. According to the grid voltage sags in different degrees, different control strategies are adopted, one is to improve the traditional control strategies, the other is to set the crowbar circuit in the rotor side.At last a detailed study of the bypass resistance and switching time in crowbar circuit is done. the simulation results show that the above control method can improve the low voltage ride through capability of double-fed wind power generator system effectively.