Control and experiment of modular multilevel converter with tuned filters for wide frequency range operation

摘要

As the fluctuation of sub-module capacitance voltage when MMC operates at low frequency, the application of MMC in the field of motor drive has been limited. Therefore, this paper proposes a low frequency control method for the MMC with tuned filter circuit. Based on the theoretical analysis for this tuned filter, the circulating current of 2^nd frequency could be suppressed effectively at rated frequency. The tuned filter also enables the minimum voltage that is adopted to control high frequency circulating current at low frequency by feasible parameters. In addition, design of circulating current controller is simplified, because the high frequency circulating current with mixed and variable frequency is no longer needed in this strategy. Zero-error tracking to the hybrid reference current is achieved by proportional integral resonant (PIR) control. Finally, the accuracy of analysis and effectiveness of proposed strategy are proved by a prototype experiment.