Patent ID: 9520800
Filing Date: 2016-12-13
CPC Classification: H02M

Claim Text:
1. A power conversion system, comprising: a DC bus circuit comprising first and second DC bus terminals; a rectifier including a plurality of multilevel rectifier converter stages, individual ones of the multilevel rectifier converter stages comprising an AC input terminal adapted to receive AC input power from a corresponding one of a plurality of AC input phases, a pair of DC output terminals individually coupled to a corresponding one of the first and second DC bus terminals of the DC bus circuit, and a multilevel rectifier circuit operable according to a corresponding set of rectifier switching control signals to convert AC input power to provide a DC output voltage at the DC output terminals; an inverter including a plurality of multilevel inverter stages, individual ones of the multilevel inverter stages comprising a pair of DC input terminals individually coupled to a corresponding one of the first and second DC bus terminals of the DC bus circuit, an AC output terminal adapted to provide AC output power directly or indirectly to a corresponding one of a plurality of AC output phases to drive a load, and a multilevel inverter circuit operable according to a corresponding set of inverter switching control signals to convert DC input power from the DC bus circuit to provide an AC output voltage at the AC output terminal; and a controller providing the rectifier and inverter switching control signals to facilitate offsetting of common mode voltage contributions of the rectifier and the inverter; wherein the individual multilevel converter stages of the rectifier and of the inverter are configured to provide an integer number N AC voltage levels, where N is an even number greater than or equal to 4; wherein the controller provides the rectifier and inverter switching control signals via space vector modulation according to corresponding rectifier and inverter reference vectors using a corresponding subset of possible switching states with minimal absolute common mode voltages; and wherein the controller provides the rectifier and inverter switching control signals using the same subset of possible switching states when a modulation index associated with the rectifier reference vector is less than or equal to a predetermined value and a modulation index associated with the inverter reference vector is less than or equal to the predetermined value.