The Simulation And Study Of Control Strategy Of Doubly-Fed Induction Generator System

Wind power is a green power which is regenerative and clean. Because of the shortage of general energy sources and the problems caused by overusing the general energy sources, the exploitage of wind power make great sense.In this thesis, firstly, based on the complex vector model of doubly-fed induction generator (DIFG), the mathematic model is deduced under the synchronous coordinate. The research provides the base to carry out the flux orientation vector control strategy. As to the model, the expressions and relationships of the torque, power, current and voltage in the rotor and stator are analyzed, indicating the state of the DFIG and the direction of power flow under different wind speed.Secondly, the control strategies of each module of AC-DC-AC double-side PWM converter used in DFIG was discussed. In order to conquer the problem that decoupled effect relies on the precise of the model, and then the method of Internal Model Control is introduced. Double-side PWM converter is composed by AC-DC rectifier module and DC-AC inverter module, and both of the two modules are connect by a DC capacitor which is used to store energy. In order to keep the voltage of the DC loop to be constant and to keep the power factor to be unit, the rectifier is controlled by vector control strategy which is based on the virtual flux of grid. The inverter on the rotor side is also controlled by vector strategy which is based on the flux of stator. In the M-T coordinate, the M axis is attached to the stator flux, and the power of DFIG can be divided into active power and reactive power, then the excitation and torque can be indirectly controlled by modulating the active power and reactive power. Therefore, the DFIG is able to output the...