A comparative evaluation of motor drive topologies for low-voltage, high-power EV/HEV propulsion systems

The recent adoption of the 42 V powernet standard for the next generation of vehicles has focused substantial research effort into the design of electric machines for light hybrid vehicles. However, research investigating the merits of topology selection for this application has been sparse. This paper investigates the potential performance benefits, which could be realized by adopting a different inverter topology. This paper discusses the merits of delta-connected motors, bipolar inverters and cascaded inverters when compared to a standard inverter. The flexibility provided by adopting a non-standard topology can produce a better overall design when one or more of the design specifications are proving difficult to meet economically with the standard topology. As a particular design example, this paper shows that a cascaded inverter topology driving an open winding motor can increase the high-speed power density of an induction motor by 73%. For an interior permanent magnet motor, this paper shows that this topology can increase low speed torque by 9% and high-speed power by up to 300%.