Combined Control Method for Grid-Side Converter of Doubly Fed Induction Generator-based Wind Energy Conversion Systems

This study proposes a combined control method based on vector control (VC) and virtual flux direct power control (VFDPC) for grid-side converter of doubly fed induction generator (DFIG)-based wind energy conversion systems (WECSs). VC gives lower power ripple with a slower dynamic response, while VFDPC provides a faster dynamic response, but higher power ripple. So, an analogy between VC and VFDPC is proved first and then used to propose a combined control method that takes the advantages of VC and VFDPC in an integrated control system. In the combined control method, the grid currents are directly controlled using hysteresis controllers and optimal switching table. It has several advantages compared to VC including faster power/current dynamic response, robustness to grid filter parameter variation, lower computation, and simple implementation. On the other hand, its advantages compared to VFDPC include less current harmonic distortion, lower power ripple, and robustness to measurement noise. To demonstrate the effectiveness and robustness of the combined control method, simulation results on a 1.5 MW DFIG-based WECS are provided and compared with both VC and VFDPC under different steady-state and transient conditions. The simulation results verify the superiority of the proposed method over either VC or VFDPC.