Novel sensorless control for pm synchronous motors based on maximum torque control frame

In this paper, a novel position sensorless vector control for IPMSMs is described. First, we define a novel coordinate frame (hereafter called the maximum torque control (MTC) frame), which has one axis aligned with the current vector of the maximum torque-per-ampere (MTPA) control and propose a sensorless control method for directly estimating the MTC frame. Because the parameter L_qmmiddot for estimating the frame is less affected by magnetic saturation than the conventional L_qm, the influence of magnetic saturation on the position estimation can be greatly suppressed. In additional, excellent current vector loci are observed even when L_qmmiddot is approximated by a constant value. This method is robust against changes in inductance caused by magnetic saturation. After defining an extended electromotive force model based on the proposed frame and a parameter L_qmmiddot for an estimation of the frame, we confirm the effectiveness of the proposed method by simulations and experiments.