Pulsating Signal Injection-Based Sensorless Control of PMSM Using Injection Axis Switching Scheme without Additional Offline Commissioning Test

In this paper, we propose an injection axis switching (IAS) sensorless control scheme using a pulsating high-frequency (HF) signal to minimize the position detection error and the velocity estimation ripple due to the zero current clamping (ZCC) effect for permanent magnet synchronous motors (PMSMs). When a pulsating carrier-signal voltage is injected in an estimated synchronous frame, the envelope of the resulting HF current measured in the stationary reference frame follows an amplitude-modulated pattern. Using this information, the IAS technique allows avoiding multiple zero-crossings of HF currents by adjusting the current phase angle 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 loaded condition, the injection voltage is switched to the q-axis and the d-axis current drops back to zero. Thus, the proposed sensorless control enforces a much better estimation performance during ZCC region without a predefined offline commissioning test than the standard pulsating injection scheme. The performance of the proposed approach is demonstrated by experimental results.