Novel Anti-Rotating D-Axis Signal Injection-Based Inductance Asymmetry Compensation for High Frequency Signal Injection Sensorless Control of IPMSMs

Inductance asymmetries introduce the 2nd-order harmonic estimated position error in the high-frequency (HF) signal injection (HFSI) sensorless control. To address this issue, a novel anti-rotating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis signal injection-based compensation method is proposed. The anti-rotating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis rotates in the opposite direction to the estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis at the same frequency, and its initial phase relative to α-axis depends on inductance asymmetry level. An additional HF voltage signal with the same injection frequency and injection phase as the one for position estimation but with an asymmetry level dependent amplitude is injected into the anti-rotating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis, generating a compensation signal to cancel the 2nd-order harmonic error in the demodulated HF current response. Two online estimators are established to determine the inductance asymmetry dependent initial phase of the anti-rotating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis and the amplitude of the injected voltage signal, respectively. It is also proved that these two parameters are almost independent of load and speed and thus can be fixed after estimation. Hence, acting as a feedforward control, the proposed method achieves a fast dynamic performance. Experimental results confirm that the proposed method effectively reduces the 2nd-order harmonic position error under both dynamic and steady-state conditions.