Improved predictive current control for unbalanced stand-alone doubly-fed induction generator-based wind power systems

This study proposes an improved predictive current control (PCC) strategy for unbalanced stand-alone doubly-fed induction generator (DFIG)-based wind power systems. The proposed control scheme predicts an appropriate average rotor voltage vector in next switching period to eliminate the rotor current errors in the following control period. The identified voltage vector sequence is then applied to the rotor-side converter (RSC) by using space-vector modulation with constant switching frequency. To increase the control accuracy, a proposed compensation method for the control time delay inherent in the digital implementation, mainly due to the sampling and calculation processes, is adopted. The whole control algorithm is performed in the RSC to achieve the desired control output, that is, compensation for the stator voltage imbalance. In addition, the effect of parameter variation on the performance of the control scheme is also considered. The proposed PCC method was tested by both simulations and experiments with 2.2 kW DFIG feeding an unbalanced load to demonstrate the excellent steady-state performance as well as the extremely fast dynamic response of the proposed current controller.