Negative-Sequence Current Compensation-Based Coordinated Control Strategy for Dual-Cage-Rotor Brushless Doubly Fed Induction Generator Under Unbalanced Grid Conditions

In this article, we propose a negative-sequence current compensation-based coordinated control strategy for dual-cage-rotor brushless doubly fed induction generator, where the machine-side converter (MSC) and the grid-side converter (GSC) cooperate to mitigate the imbalance in the control winding current, total output power, and total grid current. Based on the machine dynamic model withstanding unbalanced grid voltage, the negative-sequence current references, including four targets for MSC and three targets for GSC, are calculated and sent to the inner-current-loop controllers, where the GSC current controller is designed based on the supertwisting sliding-mode control with the stability analyzed. This proposed control strategy omits the outer-loop controller in the negative-sequence frame, which has a more simple control structure and becomes more easy-implemented. Finally, the whole proposed coordinated control system is designed and implemented in both simulation and experiments under unbalanced grid conditions, verifying the effectiveness of the proposed control strategy.