Position Sensorless Control of PMSM Drives Based on HF Sinusoidal Pulsating Voltage Injection

High frequency sinusoidal pulsating voltage injection has been one of the best solutions in low speed for sensorless control. In the process of HF voltage injection, position signal demodulation plays a key role. Conventional sinusoidal demodulation is widely used. However, it has an intrinsic defect, which leads to the necessity of low-pass filter ( LPF ) to eliminate the high frequency ripple in estimated position. Thus, the cube of HF current in q-axis is used as the position signal carrier. This process of nonlinear demodulation, which means nonlinear reaching law, is used to obtain the position deviation from HF current response. Experimental results conform the advantages of proposed method.