AN ENERGY CONTROL METHOD FOR MODULAR MULTILEVEL DC-DC CONVERTERS OPERATING WITH TRAPEZOIDAL WAVEFORMS

Abstract

In this paper, an energy control scheme is proposed for a Modular Multilevel DC-DC converter (MMC-DC-DC) operating with trapezoidal waveforms. In a trapezoidal wave-shaping, the cell capacitors are switched at fundamental frequency and they are all inserted for the majority of a half cycle and all bypassed for most of the other half, making the energy control more challenging. The proposed energy control method is obtained by controlling the duty cycle of one submodule (SM) to modify the average voltage and to add the amount of power required for energy correction. A simulation system for a 10MW, 20kV-20kV MMC-DC-DC converter has been built in PLECS to validate the proposed control method.