Analysis and Control of Modular Multilevel Converters using Discontinuous Modulation

This paper proposes a simple and generalized approach of an adaptive zero–sequence voltage injection to control the modular multilevel converter with reduced switching losses and capacitor voltage ripple. In this method, a simple approach based on the location of the voltage vector mapping to a two–level space–vector diagram is presented to determine various zero– sequence voltage components. A generalized control structure is established to conduct the perform studies among different ZSV components. Moreover, a real–time electro–thermal model is developed in PLECS platform to analyze the thermal loading on power devices. The performance and effectiveness of the proposed approach is analyzed through detailed hardware-in-the-loop experimental studies. Finally, the performance of MMC with different zero–sequence voltage injections are holistically evaluated to determine the best possible sequence in terms of reduced capacitor voltage ripple and power losses.