Sensorless control of the electrolytic capacitorless drives using the novel structure extended state observer

The traditional extended state observer (TESO) exhibits low-pass filtering characteristics in its transfer function, resulting in phase lag in the estimated back electromotive force (BEMF) in sensorless control, thereby increasing the position estimation error. For electrolytic capacitorless drives, the DC side bus voltage contains harmonics that are 6 times the frequency of the grid voltage. These bus voltage harmonics can cause harmonics in the BEMF of the motor. When using the sensorless control method based on the fundamental wave model, the harmonics of the estimated BEMF will ultimately cause position estimation errors. In response to the above issues, this article proposes a novel structure extended state observer (NSESO) for sensorless control of permanent magnet synchronous motor electrolytic capacitorless drives. The NSESO has no phase shift or amplitude attenuation at the center frequency, which can effectively reduce the phase lag of TESO. At the same time, the NSESO can effectively suppress the motor BEMF harmonics caused by harmonics in the DC side bus voltage, thereby effectively reducing position estimation errors. Finally, the effectiveness of the proposed NSESO is validated on a 2kW PMSM experimental platform.