Voltage equalization control of three-phase cascaded H-bridge multilevel rectifiers.

According to the structure and characteristics of a three-phase cascaded H-bridge (CHB) of a high-power multilevel converter, the problem of DC side voltage imbalance in practical applications and the disadvantage where the complexity of the traditional centralized control voltage equalization scheme increases rapidly with an increase of the number of modules both need to be solved. In addition, with the characteristic that distributed control is conducive to the expansion of the system to high-power and multi-module cascade, a new quasi-distributed equalization control strategy is proposed in this paper. The new equalization control strategy combines the traditional closed-loop control with the modulation ratio correction method. On the basis of the traditional closed-loop control, an equalization control module is added to realize a balanced output of the DC side voltage. The control of the equalization control module is simple and flexible, and the complexity of the overall control algorithm is independent of the number of modules. Finally, the correctness and reliability of the control method are verified by experiments. [ABSTRACT FROM AUTHOR]