Loss Reduction of Modular Multilevel Converter with Balancing Circuit for Low-Voltage Grid Converter

This study proposes a modular multilevel converter by applying a balancing circuit with a resistor for a low-voltage grid converter. The proposed balancing circuit, which is controlled by the same gate signal as that of the main switch, can reduce the loss of the additional balancing circuit and the current rating of the balance switch without the need for additional the cell capacitors. Only one voltage sensor per converter arm is required to automatically balance the cell capacitor voltages. The experimental results indicate that the cell capacitor voltages are well balanced during a rated operation of 10kW and a high efficiency of up to 99.2% is achieved, which is almost the same as that without a balancing circuit.