High Frequency Voltage Injection Method for Sensorless Control Using Single DC-Link Current Sensor in IPMSM Drives

Saliency-based sensorless control based on current derivative measurements offers improved position estimation accuracy in single current sensor systems, but it typically requires a modified pulsewidth modulation (PWM) to secure a minimum time of active vector (Tmin). This article proposes a high-frequency voltage injection (HFI) method without modifying the PWM scheme, where both magnitude and direction of the injected voltage are determined to ensure the Tmin. First, the proposed method ensures the Tmin of six active vectors, thereby eliminating parameter dependency in position estimation. In addition, a zero vector distribution strategy is introduced to reduce the current ripple induced by the additional HFI. Experimental results verify that the proposed method achieves a position estimation error below 0.05 rad and reduces current ripple by 35% without any PWM modification.