Adaptive and Nonadaptive Speed Estimation for Stability Improvement of Sensorless Induction Motor Control for Electric Vehicles

This study proposes a reactive torque flux control (RTFC) and modified speed estimation of a speed observer based on multiscalar control of an induction motor (IM) traction drive for electric vehicles (EVs). It employs an extended-speed adaptive and nonadaptive speed estimation with a stabilizing function to improve the low-speed stability of sensorless IMs. An approach for rotor speed estimation using machine models of multiscalar control plus the stabilizing function is used to control the IM. The proposed RTFC controls the flux of IM drives, in which the reactive torque component replaces the flux control target used in the Direct field-oriented control (DFOC). As a result, it resolves one PI tuning issue. The modified speed estimation design strategy for adaptive full-order observers to address the challenge is proposed to eliminate the unstable zone during a low-speed regenerative mode of operation. The pole placement method is used to select the stabilizing function gains to minimize anticipated rotor speed errors and increase resilience against parameter uncertainties at regenerating mode and low-speed operation. The proposed speed estimator performance is compared to motor speed throughout several driving profiles of EVs, including motoring, constant speed, low and zero speed, and regenerating modes of operation. The proposed RTFC approach requires only one PI controller for the reactive torque flux control. Though the scheme has a comparable performance to one with an additional flux controller, as in DFOC, it significantly reduces the computational burden. The results show that the proposed speed observer performs well across various driving profiles, and using an adaptive full-order observer (AFO) for modified speed estimation of sensorless control in EV is effective and stable. Experimental studies are carried out on a three-phase, 5.5 kW induction motor to validate the effectiveness and performance of the proposed control scheme.