A simplified sensorless vector control based on the average of the DC bus current

This paper describes a simplified sensorless vector control for permanent magnet synchronous motors (PMSM) using the average of the DC bus current. This method sets up the drive control system at relatively inexpensive because the micro controller does not need to have a precise timer and the calculation load is slight. The proposed method effectively changes two different current estimation methods in accordance with the operation mode. First, the controller estimates d-axis current and identifies back-EMF parameter in synchronous operation mode at the low speed region. The identification error of back-EMF parameter affects efficiency of the proposed system, so it needs to be zero. Second, the controller estimates q-axis current in vector control mode. The identified parameter and q-axis current define voltage reference to realize high efficiency drive. Experimental results confirm the effectiveness of proposed method.