A Medium-Voltage High-Power Cascaded Motor Drive System with Low Voltage Fluctuation in the DC Bus

To reduce the low-frequency voltage fluctuation in the DC bus of conventional medium-voltage high-power cascaded H-bridge motor drive systems, this paper proposes a topology solution using quad-active-bridge DC/DC converters. The proposed system eliminates the instantaneous fluctuating power from three converter cells through a high frequency link. This removes the need for large filter capacitors in the DC bus and the reliability is improved. Meanwhile, the multi-winding (zig-zag) transformer in the conventional cascaded H-bridge motor drive system can also be removed because of the high frequency transformer included in the quad-active-bridge DC/DC converter. The proposed topology has advantages such as higher reliability by removing the low-frequency filter capacitors, and higher power density by removing the multi-winding transformer. Simulation and experimental prototypes have been built and validated the feasibility of the proposed medium-voltage high-power motor drive system.