Voltage Balancing Method Based on H_∞ Optimal Control for Single-phase Cascaded H-Bridge Rectifiers

Traditional proportional-integral-based (PI-based) voltage balancing control (VBC) for single-phase cascaded Hbridge rectifiers (CHBR) suffer from unsatisfactory dynamic performance. An H_∞-VBC approach is thus proposed in this paper to address this issue. The relationship between difference of dc-side voltage square and power is deduced, which is used to construct a new feedback closed-loop for VBC system. Compared with PI-based control method, the merit of H_∞ approach is tracking performance and disturbance suppression can be quantitatively solved through sensitivity weighting function. Considering external disturbance on control output, an H_∞-VBC strategy is designed for specified frequency bands. With the proposed method, dynamic performance of voltage balancing is improved. An experimental prototype is developed, and experiments are performed to verify effectiveness of the H_∞-VBC strategy.