Characterization of a Hybrid PM Generator Using a 32-Phase Brushless Excitation Scheme

This paper presents characterization and operational envelope of a hybrid permanent magnet (HPM) generator in a series hybrid electric vehicle (SHEV) powertrain. A proposed control strategy is applied to characterize the system during vehicle operation within new european driving cycle (NEDC). The HPM generator utilizes a permanent magnet topology assisted with a wound field (WF) rotor while the machine 9-phase output is rectified and connected to the SHEV main dc-link. A brushless exciter with dc stator and multiphase rotor is designed to provide an adjustable dc current and voltage to the HPM generator WF. The brushless exciter dc stator is fed from the vehicle dc-link using a dc/dc converter while its rotor output connects to an integrated 32-leg rotating rectifier the output of which provides a high quality dc to the HPM generator WF. A control strategy incorporating a dynamic model of the HPM generator, brushless exciter, and dc/dc converter is proposed under which the system operational envelope is obtained. The HPM generator efficiency map, torque speed, and WF current behavior is analyzed to realize an optimum operating region while the SHEV operates over the NEDC driving cycle. The analytically predicted results are validated against measurements from a laboratory prototype HPM generator and exciter system. The comparison shows the effectiveness of the control method and accuracy of the developed models.