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 K 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 K.