Robust maximum torque per ampere (MTPA) control of PM-assisted SynRM for traction applications

Recently, permanent-magnet-assisted (PMa) synchronous reluctance motors (SynRMs) have been introduced as a possible traction motor in hybrid electric vehicle applications. In order to achieve maximum torque per ampere (MTPA), knowledge of the motor parameters is necessary. Due to the high ambient temperature inside the engine cavity as well as the saturation effect, variation of motor parameters such as inductances and permanent magnet (PM) flux density is not avoidable. Offline models for estimating the motor parameters are known as a computationally intensive method, particularly, when the effect of cross saturation and PM flux deterioration are included. In this paper, a practical MTPA control scheme, along with a simple parameter estimator for the PMa SynRM, is introduced. This method is capable of maintaining the MTPA condition and stays robust against motor parameter variations. To verify the validity and feasibility of the proposed controller, several simulations and experiments results on a low-power laboratory prototype PMa SynRM have been presented.