A flexible DC voltage balancing control based on the power flow management for star-connected cascaded H-bridge converter

This paper presents the flexible dc capacitor voltages balancing control method for star-connected cascaded H-bridge converters. In this paper, the power flows are analysed by investigating all the converter´s control freedoms. Based on the analyses, users can accomplish dc capacitor voltage balancing with both negative-sequence current and zero-sequence voltage. These two kinds of control options are further integrated together with the defined weighting factor μ. The low-voltage ride-through operation of proposed control method is also discussed in this paper. The control method is verified with a 220-V 1kVA STATCOM based on star-connected cascaded H-bridge converters, and the experimental test results show that all the dc voltages are well-regulated at the commanded value with different weighting factor μ.