Sensorless Control of IM Based on Stator-Voltage MRAS for Limp-Home EV Applications

This paper proposes a novel sensorless speed estimation for an induction motor (IM) based on a new stator-voltage model reference adaptive system (Vs-MRAS) scheme. This is utilized for torque-controlled drive (TCD) based on indirect rotor field oriented control technique in limp-home mode operation of electric vehicles (EV) applications. The Vs-MRAS scheme uses the error between the reference and estimated stator-voltage vectors and estimates the synchronous speed. Unlike existing MRAS schemes, the proposed sensorless scheme does not require the measured nominal values of stator resistance, stator inductance, and rotor resistance. This scheme is insensitive to variations of the aforementioned parameters. Moreover, using the proposed scheme eliminates the need for slip calculation. The proposed scheme is implemented and experimentally tested in a lab environment, on a 19-kW IM, and also applied on an electric golf buggy, powered by a 5-kW IM. The experimental results show that the proposed scheme is immune to parameter variations and is consistent in vehicle-starting from standstill and hill-starting tests. This scheme is also free from drift problems associated with a pure integration and is stable in the field weakening region. The test-drive results from the golf buggy confirm suitability of the proposed Vs-MRAS scheme over a wide range of speeds for the purpose of TCD in EV applications.