A Low-Speed, High-Torque Motor Drive Using a Modular Multilevel Cascade Converter Based on Triple-Star Bridge Cells (MMCC-TSBC)

This paper provides experimental verification of a modular multilevel cascade converter based on triple-star bridge cells (MMCC-TSBC) for a low-speed, high-torque motor drive. The TSBC is one of direct ac-to-ac power converters capable of achieving bidirectional power flow and drawing/feeding three-phase sinusoidal input (supply-side) and output (motor-side) currents with any power factor at both sides. This paper designs, constructs, and tests a downscaled drive system combining a 400-V, 15-kW, phase-shifted-carrier PWM TSBC equipped with four bridge cells per cluster and a 320-V, 38-Hz, 6-pole, 15-kW induction motor loaded at the rated torque. Experimental waveforms obtained from the downscaled drive system verify stable operation across a broad range from a standstill to the rated speed, showing satisfactory start-up performance.