Integrated Control of an IPM Motor Drive and a Novel Hybrid Energy Storage System for Electric Vehicles

A dc bus voltage control for a motor drive that uses a hybrid energy storage system (HESS) for electric vehicle applications is proposed in this paper. The HESS is composed of a high energy density battery pack along with a high power density ultracapacitor. The motor drive of an interior permanent magnet (IPM) motor is conventionally designed based on a fixed dc bus voltage. However, with the voltage controllability of the HESS, it is possible to enhance the system efficiency by selecting the optimum dc bus voltage. Unlike conventional designs, the proposed HESS processes only a portion of the vehicle power through an interfacing dc/dc converter. This new concept reduces converter losses, enables full usage of the energy stored in the storage devices, and provides a boosting capability of the dc bus voltage. Consequently, the motor drive operates with maximum torque per ampere control for an extended operating range. An electric vehicle, equipped with a HESS and an IPM drive is simulated under different driving conditions. Experimental results of a prototype system are provided to verify the system effectiveness.