Transient error compensation in sensorless control of PMSM

Sensorless schemes based on HF carrier injection are capable of estimating rotor position in a wide speed range. In these schemes first an additional HF voltage is injected to stator windings. The corresponding HF current is decoupled from main stator currents and the position of the rotor saliency is estimated based on the decoupled HF current in a closed loop tracking observer. The tracking observer is capable of tracking rotor saliency with no steady state error. Transient error appears when the motor starts to move or whenever the rotor speed changes because of any disturbance or any change in the rotor speed command. In this paper a new solution is proposed in order to compensate for the transient error in estimation of rotor position.