Pulsating Signal Injection-Based Axis Switching Sensorless Control of PMSM for Minimal Zero Current Clamping Effects

This paper proposes an injection axis switching (IAS) sensorless control using a pulsating HF signal to minimize ZCC effect for permanent magnet synchronous motors (PMSM). When a pulsating carrier-signal voltage is injected in a synchronous frame, the envelope of the resulting HF current measured in the stationary reference frame follows an oscillating pattern with a maximum to zero magnitude. Taking this effect into account, multiple zero-crossings of HF currents around the zero-crossing region can be avoided by adjusting the current phase angle according to the load condition. For this purpose, we develop an injection axis switching scheme according to the load condition. At no-load, the pulsating voltage is injected only on the d-axis while the d-axis current is controlled to a certain nonzero value. Under the load condition, the injection voltage is switched to the q-axis and the d-axis current drops back to zero. Thus, the proposed sensorless control permits the HF current magnitude to be zero at every zero-crossing point. The minimization result leads to an accurate position estimate during ZCC region and the proposed scheme does not require any additional test prior to start-up. Experiments demonstrate the superiority of the proposed method in suppressing the voltage distortions caused by ZCC effect.