Simultaneous Rotor Time Constant and Speed Estimation for Speed-Sensorless IM Drives with a Shift Angle

For speed sensorless induction motor drives, there are a number of methods for simultaneous rotor time constant and speed estimation. However, the coupling of speed and rotor time constant estimation is a well-known problem. To cope with this problem, this paper presents a simultaneous rotor time constant and speed estimation method with a shift angle. In contrast to existing methods, this paper analyzes the coupling between rotor time constant and speed based on the adaptive laws. Then, rotor time constant and speed are decoupled using a compensation method based on a shift angle. In the rotor flux estimation, the rotor position error, which is neglected in the conventional methods, is introduced to improve the estimation accuracy. By analyzing the selection of shift angle, it is proposed to remove the rotor time constant estimation under light load condition. Finally, the effectiveness of the proposed method is verified on a 2.2kW IM setup.