New Combined Maximum Torque per Ampere-Flux Weakening Control Strategy for Vehicle Propulsion System

The control of electric vehicles (EVs) is ensured by the control of their in-wheel motors of electric traction chains. This article presents a new control strategy of an interior permanent-magnet synchronous motor (IPMSM) used in electric traction applications for high-speed operation, by combining maximum torque per ampere (MTPA) control at low speeds and flux-weakening (FW) control at high speeds. This strategy allows to control with high precision and independently the torque applied to each in-wheel motor while ensuring high torque at high speeds, which is important for embedded systems. IPMSMs have been considered as a potential candidate for EV applications due to their best power density and efficiency. To ensure optimal operation of the IPMSM, a key element for the stability of the EV, the concept of the proposed method leads to combine two torque control strategies and divides the torque/speed characteristics into two zones. The validity of the proposed strategy was proved by the simulation results carried out under Matlab/Simulink. The numerical simulation of the system shows that this combined control strategy (MTPA-FW), based on the vector control of an IPMSM powered by a two-level voltage inverter, allows to offer excellent dynamics of the traction system in a wide operating speed range.