A novel modular multilevel inverter for medium-voltage open-end split winding machines based on single-phase submodules with input-series connection

Abstract

In this paper, a modular inverter topology conceived by input series connection of H-bridge (ISHB) is presented and verified trough experimental results. The proposed converter is naturally appropriate for open-end split winding induction motor drive due to the galvanic isolation offered by the machine. Each sub-module is composed by a H-bridge inverter, which is characterized for a modulation with three levels, using phase-shifted PWM modulation strategy. All bus capacitor related to a phase of inverter are connected in series to reach the desired voltage level that is required in high power and high input voltage applications requirements. The proposed structure has a voltage self-balance in the series-connected input capacitors, which provides a stable operating point and ensures proper power distribution between each submodule. A prototype was build in order to validate the theoretical results for a 7.50kW induction motor, that has three-open winding per phase.