Estimation of thermally de-rated torque of an HEV drive using robust LPV observer

Abstract

A robust LPV observer has been designed to estimate the thermally de-rated torque of an hybrid electric vehicle (HEV) induction machine drive. The torque performance of conventional field-oriented control (FOC) deteriorates under the vast uncertainties in rotor and stator resistance due to the temperature variations during the HEV operation. Similar worsening of the response is expected due to the wide variations in rotor speed in HEV application. To cater for these uncertain scenarios, a robust observer is designed to estimate the de-rated torque performance so that the overall performance of HEV drive system can be improved. The robust observer is based on the linear parameter varying (LPV) technique. The stability of proposed robust LPV observer is also established. The proposed algorithm has been tested in shortened FUDS test cycle for HEV electric power-train. The nonlinear simulation results confirm the observer capability to successfully estimate the de-rated torque in the HEV electric drive in both theoretical and practical scenarios.