Sensorless control of induction motor drives equipped with inverter output filter

This paper deals with the speed sensorless vector control of an induction motor in a special case where the output voltage of the PWM inverter is filtered by an LC filter. The system states are estimated by means of an adaptive full-order observer, and no additional voltage, current or speed measurements are needed. The rotor speed adaptation is based on the estimation error of the inverter output current. Dynamic analysis is used to find an observer gain that enables a wide operation region, including very low and very high speeds. A torque-maximizing control method is applied in the field-weakening region. Simulation and experimental results show that the performance is comparable to that of a drive without the LC filter.