Position and MTPA Current Phase Estimation Method at Low Speed for IPMSMs Based on Flux Model Suitable for Maximum Torque Control

Abstract

This paper proposes a new estimation method for the position and current phase of maximum torque per ampere (MTPA) operations at low-speed based on the “L_d model”, which is a robust mathematical model designed to address magnetic saturation in interior permanent magnet synchronous motors (IPMSMs). In general, sensorless control techniques based on high frequency signal injection can guarantee reasonable torque control performance even at zero speed. The motor parameter variation of most method is robust. However, the MTPA control in those methods requires q-axis inductance that significantly varies owing to magnetic saturation. Therefore, a parameter mismatch may occur that decreases motor efficiency and reduces operation range. As mentioned above, this paper proposes a new position sensorless MTPA control method based on the L_d model.