Enhanced operation for DFIG-based WECS using resonant feedback compensators under grid unbalance

In this paper, an collaborative operation and control of the rotor side converter (RSC) and grid side converter (GSC) for a doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) is presented during grid unbalance. The RSC is controlled to achieve the four different control targets, including sinusoidal stator or rotor current, or constant stator output power, or constant electromagnetic torque. And the GSC is designed to provide a stable DC voltage. An additional feedback compensator using a resonant regulator for RSC is employed to avoid the positive and negative components decomposition, meanwhile another similar compensator is applied in GSC to suppress the DC voltage fluctuation without the need to detect the rotor or stator power, and the GSC reactive power oscillations is also removed. Simulation and preliminary experimental results validate the effectiveness of the proposed control strategy under the unbalanced voltage conditions.