Initial Rotor Position Estimation for Low Saliency Interior Permanent-Magnet Synchronous Motor Drives

This paper presents an initial rotor position estimation method for low saliency interior permanent-magnet synchronous motor (IPMSM) drives. The method injects signals into the stationary alpha-beta frame of the motor and substitutes the injected signals into the stationary alpha-beta frame model of the motor to solve for the rotor position. In particular, the method injects specific signals into the motor to eliminate the rotor-position-independent terms while keeping the rotor-position and motor-saliency dependent terms in the motor model. As a result, the rotor-position and motor-saliency dependent terms are invulnerable to errors or noise in the rotor-position-independent terms and therefore when used to solve for the rotor position, lead to accurate results in rotor position estimation. Experimental results show that the position estimation error is less than 5 degrees electrical for a low saliency IPMSM whose d-axis and q-axis inductance are 1.65mH and 1.70mH respectively.