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

A DC bus voltage control for a motor drive is proposed in this paper using a hybrid energy storage system (HESS) composed of a battery and an ultra-capacitor for electric vehicle applications. The motor drive of an interior permanent magnet (IPM) motor is typically developed based on a fixed DC bus voltage. However, with the voltage controllability of HESS, it is possible to optimize the energy system by selecting the optimum DC bus voltage. Unlike the conventional designs, the proposed HESS processes only a portion of the vehicle power through interfacing a DC/DC converter. The new concept reduces the converter losses, enables the full usage of stored energy in the storage units and provides a boosting capability of the DC bus voltage. This capability allows the motor drive to operate with maximum torque per ampere control for longer time intervals. An EV with HESS and an IPM drive is simulated under different driving conditions to demonstrate the concept. Experimental results of a scaled down system are provided.