A speed observer for speed sensorless control of induction motor

This paper proposes a novel speed sensorless control strategy for induction motor drives based on active-disturbance rejection controller. Based on the field-oriented control technique, the dynamic model of q-axis current is a first order nonlinear state equation including synchronous speed and rotor speed. The synchronous speed and rotor speed is regarded as the internal disturbance of q-axis current. According to the active-disturbance rejection controller theory (ADRC), the system uncertainties and disturbance could be estimated and compensated instantaneously. Once the disturbance including rotor speed is estimated in real-time, rotor speed is also observed from it. With the help of the extended state observer (ESO) and state error feedback control law (NLSEF), the speed observer proposed in this paper realizes the disturbance compensation accurately without the knowledge of the exact system parameters. Simulation results show that the rotor speed can be accurately estimated from 0r/min to rated speed with load or not. A good dynamic and static performance of the sensorless vector control system is achieved by this method.