Analysis of position estimation error resulted from filter in carrier signal injection based sensorless control of PMSM

Position estimation errors resulted from filters in carrier signal injection based sensorless control of permanent magnet synchronous motor (PMSM) are analyzed. Expressions of position estimation error are derived for both rotating and pulsating voltage injection method when the stator resistance and filter´s characteristic are taken into account. It is shown that influences of the filter on above two methods are quite different. In rotating injection, the position estimation error includes two components attributed to the stator resistance and the filter respectively. The latter is determined by the lagging phase angle of the filter at frequency (ω_c-2ω_r). It is independent of motor parameters and can be compensated easily and perfectly. In pulsating injection, the error is determined by the difference of lagging phase angles of the filter at (ω_c+ω_r) and (ω_c-ω_r), and strongly depends on motor parameters. In a motor with low L_q/L_d, the pulsating injection method without compensation may fail to track the rotor position at high speed. Compensation methods are proposed. The theoretical results are verified by simulations.