Effect of the Inverter Non-linearities Compensation on a MRAS Speed Estimator in a Double Fed Induction Motor Drive

Some double fed induction machines require low rotor voltages and frequency when operating close to synchronous speed. In these conditions, the effect of inverter non-linearities becomes weighty and cannot be neglected. This paper proposes a compensation algorithm for the switch voltage drops and for the dead time of the inverter. The suggested algorithm corrects the switches on-state durations instead of the reference voltages. Some different i − v characteristics of semiconductor switches are taken into account. Experimental results based on a space vector modulation strategy are reported. Experimental tests are performed on a sensorless machine. The influence of the voltage compensation on a MRAS speed estimation is highlighted.