Managing Thermally Derated Torque of an Electrified Powertrain Through LPV Control

Vehicle with electrified powertrains exhibit degraded performance when operated in hot environments. When the operating and surrounding temperatures rise, an electric drive suffers from torque derating as its parameters change. This paper proposes a linear parameter varying (LPV) based observer controller pair to address this problem. The feedback field oriented control (FOC) is the most commonly adopted instantaneous torque control method for an electrified powertrain drive system. The flux and torque performance of a conventional feedback FOC deteriorates under the vast uncertainties in rotor and stator resistance due to temperature variations during electric vehicle (EV) operation. To cater for these uncertain scenarios, a robust closed-loop observer is designed to estimate the thermally derated torque and flux. The stability of the whole LPV scheme is established. The efficacy of the proposed algorithm is demonstrated for an EV operating in federal urban driving schedule with a dynamic temperature profile. The nonlinear simulation results confirm the LPV observer capability to successfully estimate the flux and derated torque in an EV drive system. The proposed technique, after validating in simulation environment, is verified experimentally on an induction machine drive controlled by NI myRIO-1900.