Research On Low Voltage Ride Through Of Doubly-fed Wind Power System Based On Sensorless

Along with the increase of the installed capacity of wind power,the problem brought by large-scale wind power become increasingly prominent.World Governments now set strict limits on the technical requirements of grid-connected wind generator according to their actual conditions.The most important in all provisions is the low voltage ride-through(LVRT) capability.For now the mainstream wind generators is doubly-fed induction generator(DFIG). Because of its own structural feature ,it,s LVRT is difficult to achieve and always need to use a Crowbar.In order to improve the LVRT ability of the DFIG,this paper firstly analyzes the dynamic behavior of the DFIG during three-phase voltage dips and infers the reasons of rotor inrush current.Then,an improved control strategy is proposed.Unlike the traditional control method,the new control strategy use the d-axis rotor current to control the stator flux. When a voltage dip is detected on the DFIG terminal,this control scheme will give the d-component of rotor reference current and enhance the wind turbine,s LVRT capability.In the DFIG traditional control method,we need to use a sensor to obtain the rotor speed and angle.But wind turbines always work in bad conditions,then this sensor will increase the costs and minmize reliability,so in this paper ,a sensorless method for the vector control of DFIG is proposed.The proposed sensorless method is based on the Model Reference Adaptive System(MRAS) estimating the rotor speed and position from the rotor current.At last,the new LVRT control strategy and the sensorless control of DFIG will be combined to study a sensorless control of DFIG,s behavior when there is a voltage dip at the DFIG terminal.The simulation results prove that the control method is correct.