Experimental verification of a modular multilevel cascade converter based on triple-star bridge-cells (MMCC-TSBC) for motor drives

This paper presents the modular multilevel cascade converter based on triple-star bridge-cells (MMCC-TSBC) with a focus on experimental verification for motor drives. The TSBC is one of the direct ac-to-ac power converters, which is characterized by achieving bidirectional power flow, drawing and feeding three-phase sinusoidal input (supply-side) and output (motor-side) currents with any power factor at both sides. Therefore, it is suitable especially for a low-speed, high-torque application of a medium-voltage high-power motor drive requiring regenerative braking. A downscaled system rated at 400 V and 15 kW is designed, constructed, and tested to confirm the validity and effectiveness of the motor drive. Experimental results show that stable operation is verified at such a low speed as 60 min^-1 with the rated torque. In addition, it is verified that the motor loaded the rated torque can start up from a standstill without producing any overvoltage or overcurrent.