Observability measurement and control strategy for induction machine sensorless drive in traction applications
Résumé
Electrical traction using induction machine sensorless control requires high observer performance for all speed ranges, even for low speed or regenerative braking conditions which appear frequently during long time. It is well known that the speed of induction motors is unobservable at very low stator frequencies. This paper uses an observability index to continuously analyze speed observability for sensorless control of induction machines. The correlation between observability-index and observer performance is illustrated in a Hardware in the Loop (HIL) experimental test-bench combining the well-known vector control with an extended Kalman filter. Thanks to the observability-index information, an optimal strategy is proposed to design controllers to guide the system away from undesirable behavior and avoid the weak observability-index region by taking into account all working constraints. A simplified case is presented to improve the speed observer performance, which was tested in the same conditions with the same HIL test-bench to experimentally validate the proposed sensorless control for traction applications.