High-efficiency multilevel converter technology for electric vehicle applications using super-junction MOSFETs

“Super-junction” MOSFETs exhibit low on-state resistances and low switching losses. However, the reverse recovery behaviour of their intrinsic diodes and their output capacitance characteristics make their use in voltage-sourced converters challenging. If these difficulties can be addressed, high efficiencies are attainable. Multilevel converters are potentially attractive topologies in electric vehicle charging and energy storage applications. Filter components may be smaller. Also, devices can be combined to give a blocking capability higher than their individual ratings. For example, where a vehicle's battery pack is being charged from or discharged into a 400V three-phase supply, SJ MOSFETs rated at 600V can be deployed in a three-level topology to give a nominal 1200V blocking capability. In this paper, the challenges presented by the super-junction MOSFET are tackled in a demonstration 720V, 3kVA, 20kHz, three-level, three-phase neutral-point-clamped converter.