An improved control method for DFIG-based wind system supplying unbalanced stand-alone loads

This paper proposes a novel control method for operation of a DFIG-based wind generator under unbalanced stand-alone loads, connected directly with stator terminal of the generator. The effect of unbalance condition at loads causes torque pulsations on generator and the stator voltage unbalance that degrade the dynamic behavior of control system. To eliminate the negative sequence components existing in generated stator voltages, the proposed compensation approach is developed based on the coordinated control of rotor-side controller (RSC) of the DFIG system. The main concern of this paper is the use of hybrid current controller (HCC), consisting of a proportional integral (PI) controller plus a resonant (R) compensator. For the sake of improvement, the HCC is executed in the positive synchronous rotating reference frame without considering decomposition of positive and negative sequence components of current values. Simulation is executed using PSIM, and experimental results are also shown in the paper to demonstrate the feasibility and efficiency of the proposed control method.