Dual-negative-objective Coordinated Control of Brushless Doubly Fed Induction Generator under Unbalanced Grid Voltage

This article proposes a dual-negative-objective coordinated control strategy for brushless doubly fed induction generator (BDFIG) based wind power generation system under unbalanced grid voltage. To alleviate the mechanical stress and impaction on rotating shaft, the negative control objective (NCO) of machine side converter (MSC) is set to suppress the ripple of electromagnetic torque. While the NCO of grid side converter (GSC) is selected to suppress the oscillation of total output active power or the unbalanced degree of total output current for BDFIG generation system. In comparison with traditional single converter control scheme of the MSC or GSC, dual NCOs can be satisfied at the same time due to the enlarged freedom degree in the proposed improved coordinated control system for back-to-back converters. The effectiveness of proposed control strategy is validated by simulation and experimental results on a dual-cagerotor BDFIG (DCR-BDFIG) prototype.