Study on Extend Kalman Filter at Low Speed in Sensorless PMSM Drives

The application of an Extended Kalman Filter (EKF) as nonlinear speed and position observer in PMSM drives has been a mature research project. However, one significant problem still unsolved is the weakly performance at low speed of PMSM drive system that yield to the best estimation performance on high speed range (≫5Hz). This paper proposes a novel method--Adjustable DC bus voltage, for low speed EKF sensorless control of permanent magnet synchronous motor (PMSM) drives. The findings from the experiment that the better performance at low speed (≫2Hz) by adjusting the DC Bus voltage according to the system reference speed are also presented. Simulation and Experimental results are given to confirm the effectiveness of the proposed method.