Robust Compensation of Position Error in Sensorless SPMSM Drives Utilizing Torque Deviation Signal Excited from Low-Frequency Current Injection

The second-order linear position observer of surface mounted permanent magnet synchronous motor (SPMSM) suffers from parameters variations, control delay, etc. Focusing on these problems, this paper proposes the low-frequency current injection method for compensation of position error. It is proved that although the absolute error of torque calculation of one work point changes irregularly with the position error, the relative error of torque calculation between two operating points changes linearly with the position error. Based on this analysis, the lowfrequency current signal is injected to excite the relative torque error sequence. The position error and relative torque error can converge to zero at the same time. In the calculation process of torque relative error, since the influence of parameter changes can be cancelled out, the method has high robustness. Experimental results validate the effectiveness and robustness of the method.