Improved Hybrid Sensorless Control for IPMSM in Full Speed Range at Low Switching Frequency

This paper proposes an improved hybrid sensorless control method for interior permanent magnet synchronous motor (IPMSM) in full speed range at low switching frequency. At low speed, the conventional high-frequency (HF) voltage injection method is difficult to implement at low switching frequency because of the special dual sampling rate mechanism. Therefore, this paper proposes an improved square wave voltage injection method, which separates the observation of rotor position from the injection of HF voltage and the extraction of HF current based on dual sampling rate mechanism. Then, the error caused by large PWM delay at low switching frequency is analyzed and compensated. At high speed, to avoid the influence of cross coupling due to discretization error on the estimated rotor position at low switching frequency, the cross coupling caused by modeling in continuous time domain is analyzed, then a state observer is established in discrete time domain directly. A 3 kW experimental platform is built to verify the effectiveness of proposed method.