Variable speed brushless hybrid permanent magnet generator for hybrid electric vehicles

Hybrid permanent magnet (HPM) generators have been proposed as engine mounted machines operating at fixed rotor speed and generating via simple passive rectifiers into a variable vehicle system DC-link voltage. As such, the machine excitation is controlled to maintain delivered power output. This paper studies the variable speed operation of a (HPM) generator in a series hybrid electric vehicle (SHEV) within some specific driving cycles. The study investigates different scenarios in terms of the possible operational regions for the HPM generator at different speeds. A HPM generator designed to deliver controlled power into a varying system DC-link voltage at fixed rotor speed is used as a reference design. Two further designs are then developed to study the impact of varying generator speed on machine design and excitation requirements. The loss analysis for the three designs is conducted including the losses in the passive rectification stages used in the system. Simulation studies are carried out for different HPM generator power levels at different speeds. The simulated performance characteristics of the HPM are validated via test data from a prototype machine and loading system.