Sensorless Control of CSI-Fed PMSM Drives Based on Improved Extended State Observer

To address the problem that the maximum error of back-EMF observers increases with an increase in motor speed, based on an extended state observer, this paper designs an angle-compensation strategy based on a proportional–integral controller and an extended state observer, according to the principle that a proportional–integral controller uses an integral link to eliminate steady-state error. After obtaining the back EMF, the proportional–integral phase-locked loop is often used to extract the angle and speed from the observed back EMF. However, this method will produce steady-state errors when the motor is accelerated, and the integration link is prone to overshoot, so it exhibits some defects. Therefore, this paper uses an extended state observer instead of a proportional–integral regulator to build an improved phase-locked loop based on an extended state observer.