High performance control of an asymmetrical six-phase induction machine using a five-level cascaded H-bridge inverter for EV drivetrains

The battery electric vehicle (EV) is the most prominent alternative to traditional fossil fuel powered cars. Most modern EVs use three-phase machines for propulsion supplied by a standard IGBT-based two-level voltage source converter connected to a single large battery pack. However, recent research has indicated that most driving takes place at low speeds and the two-level converter has been shown to be inefficient in such operating conditions. This paper describes an alternative EV drivetrain based on a multilevel multiphase drive where a cascaded H-bridge multilevel inverter is used in conjunction with a six-phase induction machine. A rotor flux-oriented control of the drive is presented with experimental validation. The drive benefits from modularity, inherent fault tolerance, low THD at low switching frequencies, fast dynamic performance, and the possibility to be used in both propulsion and battery charging modes with minimal hardware reconfiguration.