Effect of current measurement error in angle estimation of permanent magnet AC motor sensorless control

This paper discusses the effect of current measurement error in angle estimation of permanent magnet AC motor for position sensorless control based on motor back EMF. The current measurement errors due to non-ideal elements in the system are classified into the scaling error, the offset error, and the discretization error. Those errors have been represented in the estimated synchronous reference frame. The current measurement errors affect the sensorless observer input and the estimated angle. With these results, the effects of the current measurement errors on the estimated angle for the sensorless control are analyzed. Through the analysis, it has been figured out that the estimated angle for the sensorless control is directly affected by the current measurement. The analysis is verified by computer simulation and experimental results.