Application of carrier frequency signal injection in sensorless control of a PMSM drive with forced dynamics

The sensorless control of PMSM with forced closed-loop dynamics is originally an observer-based method, where the fundamental-frequency current and voltage are used for the estimation of rotor position. Experimental results show a good agreement with the estimated rotor speed for high speeds. In order to eliminate the problems occurring at low speeds, a position estimation technique based on the carrier-frequency signal injection was added to the originally proposed control scheme. The external load torque observer of the control method with forced dynamics was also used in the phase-locked loop arrangement of the signal-injection method. The results of computer simulations show that this new strategy solves the low-speed problem.