A robust V/f based sensorless MTPA control strategy for IPM drives

This paper presents a V/f control strategy for interior permanent-magnet motor (IPM) drives providing maximum torque per ampere (MTPA). It is well known that accurate rotor position information is required for vector control of interior permanent-magnet motors. As an alternative for low cost applications, open-loop V/f control method can also be employed which is inherently unstable and appropriate for narrow speed range. The proposed V/f control strategy not only delivers stable operation in a wide speed range, but also achieves stable maximum torque generation with integrated MTPA block. This close-loop V/f control algorithm includes two feedback stabilizing loops based on the rotating axis current response during the transients. One stabilizing loop is for voltage vector amplitude compensation and the other one is for voltage vector angle correction. Since no sensor or observer is required for rotor position estimation, it is an ideal alternative for cost-sensitive, low-end variable speed applications. Theoretical analysis, simulation and experimental results are provided in this paper to validate the fidelity of the proposed strategy.