Estimation method of maximum torque phase at low-speed based on robust mathematical model to magnetic saturation for position sensorless control of IPMSMs

This paper proposes a new estimation method of the maximum torque ampere (MTPA) current phase at low-speed based on an “L
_d
model”, which is a mathematical model that is robust to magnetic saturation for interior permanent magnet synchronous motors. In general, sensorless control techniques based on high frequency signal injection methods have been applied at low-speed drive. Those methods can guarantee the reasonable torque control performance even at zero speed. In addition, most of methods have robustness to motor parameter variation. However, the MTPA control in those methods requires q-axis inductance, which varies significantly owing to magnetic saturation. Therefore, a parameter mismatch may occur, which decreases motor efficiency and the operation range is narrowed. As mentioned above, we propose a position sensorless MTPA control method based on the L
_d
model.