Power Balancing Control of Sub Modules with Battery Units in Single-Phase Grid-Tied MMC Under Unbalanced Generated Power

This study proposes a single-phase grid-tied modular multilevel converter (MMC) with submodules (SMs) for small-scale renewable energy sources (RESs) and power-balancing control of SMs under unbalanced generated power. The RESs are connected to the input capacitors of the MMC. The MMC is capable of injecting the generated power without the switching ripple filters or line-frequency transformers. The SM comprised an H-bridge inverter, DC-capacitor, dual active bridge (DAB) converter and battery. The SMs balance the unbalanced power generated between each cell by charging or discharging the batteries. A computer simulation is implemented to verify the viability of the proposed system using a piece wise linear electrical circuit simulation software. Simulation results demonstrate that the DAB converters can balance the unbalanced generated power, and the system can inject power into the utility grid without degrading power quality.