A comparative study of current control schemes for a direct-driven PMSG wind energy generation system

Because of many advantages of a direct-driven permanent magnet synchronous generator (PMSG), it becomes one of the most attractive variable speed wind energy generation type. Different control strategies have been studied for controlling the machine side converter of the PMSG. This paper presents a comparative study of three current control schemes for machine side converter (MSC) based on rotor flux oriented control. Firstly, an integral sliding mode controller (ISMC) is designed to regulate the stator current in the synchronous reference frame. The proposed ISMC has two integral switching functions for stator direct and quadrature currents control. Secondly, a finite control set model predictive control (FCS-MPC) is designed to regulate the stator current and replace ISMC. The proposed MPC takes the discrete states of the voltage source inverter into account and the future converter behavior is predicted for each sampling period. Then the switching action that minimizes a predefined cost function is selected to be applied in the next sampling instant. Neither axes transformation nor modulation technique of the stator voltage is required. Finally, to evaluate the performance of the proposed controllers, their performance is compared to the conventional PI-controller under the same operating conditions. The feasibility and effectiveness of the proposed schemes have been demonstrated through computer simulations. The results show the advantages and drawbacks of each controller.