A transformerless cascaded AC-DC-AC converter for multiphase propulsion drive application

A transformerless converter which is suitable for multiphase drive system application is presented in this paper. This topology employs a cascaded H-bridge rectifier as the interface between the grid and multi inverters which drive the multiphase motor. Compared to the conventional structure, the new topology eliminates the input transformer and also has the advantages of using this topology are four quadrant operation, simple configuration, low cost, high efficiency, and so on. The control strategies for the grid-side cascade H-bridge rectifier and the motor-side inverter are studied. Based on the multi-rotational reference frame, modular control scheme is developed to regulate the multiphase drive system. Simulation results show the proper operation of the proposed topology and the corresponding control strategy.