A phase-disposition PWM method for DC voltage balance in cascaded H-Bridge rectifier

In this paper, a novel control scheme for cascaded H-Bridge rectifier (CHBR), which can be used as the primary end of high voltage high power multilevel converters, is presented. The controller is similar with the one for single phase rectifier. To improve the performance of the controller, notch filter and proportion resonance (PR) controller are employed and the discrete methods for them are discussed in detail. The different function of CHBR controller from the single rectifier is for voltage balancing. Therefore, the phase-disposition technology, which is used in the multilevel converter, is introduced to eliminate the voltage error from the expected value. With this approach, the states of the switches of the CHBR are decided correctly by the practical condition and then the DC-link capacitors of the cells are controlled to charge or discharge in the way which results to voltage balancing. The effectiveness of the proposed approach is verified by experimental results.