High Speed Generator and Multilevel Converter for Energy Recovery in Automotive Systems

"This paper deals with the design solution adopted for a high-speed axial-flux permanent-magnet generator devoted to supplementing power in automotive 42V electrical systems through a low-voltage multilevel neutral-point-clamped converter. The axial-flux permanent-magnet generator is suitably designed to be directly coupled with a radial turboexpander which provides recovery of kinetic energy available from the exhaust gases of an internal-combustion engine. The multilevel converter is properly sized for systems having low voltage and high 1st order harmonic frequency. The paper describes the proposed 4 kW power rating generating system and discusses various issues resulting from electromagnetic, thermal and mechanical design of the high-speed axial-flux permanent-magnet generator, as well investigations on modulation strategy, total harmonic distortion and power losses are presented for the low-voltage neutral-point-clamped power electronic converter."