Power balance control and circulation current suppression for MMC-based EV integration system considering users' requirements

A modular multilevel converter (MMC) is a possible solution to integrate EV fleet into grid by embedding EVs into the DC link of each sub-module of MMC. The charging/discharging power differential control strategy considering EV users' requirements in the same arm has been proposed in the previous work. However, it is also important that the balance among the power of three phase-units should be met up with meanwhile circulation current should be controlled to ensure the system operation stably. This paper proposes the control strategy of balancing power among three phase-units for MMC-Based EV fleet integrated into smart grid based on virtual SOC concept to realize the control objectives considering both EV users' requirements and utility demands. In addition, a circulation current suppressor is designed for contributing to the power balance control. Detailed system structure and control scheme are presented and a MMC-based EV integration system model is established in Matlab/Simulink to verify that the power of three phase-units can be controlled differentially considering both EV users' requirements and utility demands without affecting the output powers and currents waveforms of the system and the circulation current can be restrained.