Sensorless Vector Control for Permanent Magnet Synchronous Motor Fed by Three-Level Inverter

Three-level inverters and relative techniques have been concerned more and more in industrial drive applications because of the outstanding performance. The aim of this paper is to present a strategy for the sensorless vector control of Permanent Magnet Synchronous Motor (PMSM) drive fed with a three-level Neutral-Point-Clamped (NPC) inverter. By measuring the different current change rates which are caused by the voltage vectors applied to the motor by the Space Vector Modulation (SVM) scheme for three-level inverter, signals that contain the information of rotor position are obtained. Therefore, the rotor angle can be calculated. Since none of any prior knowledge of the PMSM parameters is used, the position estimation accuracy is not affected by the parameters variation or measurement error. Furthermore, taking advantages of the three-level voltage inverter, the ripples of torque as well as the harmonics of the phase voltages are significantly reduced. The simulation results demonstrate that the proposed strategy is effective and this system operates well over a wide speed range.