Three-Phase Modular Multilevel Converters Composed of Universal Smart Power Module

A universal smart power module (USPM) has been proposed for modularization of the power converter elements. In this paper, we propose a control method for a three-phase modular multilevel converter (MMC) composed of USPMs. The proposed control method suppresses an effect of the communication delays owing to distributed control in wireless communications. As a result of the experiment at the steady-state, it was confirmed that DC to three-phase AC conversion was achieved despite communication delays. Furthermore, the tracking performances of the line voltage and average cell capacitor voltage were improved by the cell capacitor voltage average control, and the system operation was stable irrespective of the load. As a transient response, stable operation was confirmed to be possible even when the load fluctuates and the cell capacitor command value changes in steps. The effectiveness of the proposed control method in three-phase MMC with USPM is demonstrated.