A Calibration Strategy for EV Drives Based on Improved MTPV Table Decoupled from Permanent Magnet Flux Linkage Variation

Nowadays, interior permanent magnet synchronous machines (IPMSMs) are widely used in electric vehicles. The maximum torque per volt (MTPV) is a conventional control strategy for motor control. It is a collection of current operating points that have the maximum torque corresponding to different stator flux linkages and can be used to maximize the motor torque capability in high-speed region. However, the temperature dependence of Permanent Magnet (PM) flux linkage results in variation of the MTPV boundary. Therefore, the maximum torque cannot be reached if a constant MTPV table is used. In this paper, an improved MTPV table is suggested which is based on a normalization method. The input of this table is the normalized stator flux, and its output is the normalized current reference. By doing so, this table is decoupled from the PM flux linkage and it is consistent under different PM temperatures. Also, a calibration strategy with a stator flux closed-loop control is designed to acquire the proposed MTPV table. Both the torque performance of the MTPV table and the feasibility of the calibration method are verified by simulation and experimental results.