Observer Assisted Current Reconstruction Method with Single DC-Link Current Sensor for Sensorless Control of Interior Permanent Magnet Synchronous Machines

The paper presents an observer assisted current reconstruction based method to estimate the three phase currents by utilizing only one dc-link current sensor to realize position sensorless control of interior permanent magnet synchronous machine (IPMSM). The current reconstruction technique needs dc-link current information for at least two vector transition regions in a switching period to estimate the three phase currents. However, it is challenging at the sector boundary regions (immeasurable region) without shifting the space vectors of the pulse width modulation (PWM). In the proposed method, the current estimation is assured in the boundary region without shifting the PWM vectors with the help of assistive model-based observer. The assistive model-based observer is a Luenberger type observer that estimates the back electromotive force (EMF) based on the error between the reconstructed and estimated currents. An adaptive band-pass filter is applied to the estimated back EMF to eliminate the undesirable harmonics in the immeasurable region. The proposed scheme feedbacks the estimated current to the current controller and utilizes the estimated back EMF to estimate the position and speed. The algorithm is implemented in dSpace platform and validated by experiments.