A simple high efficient torque control for the electric vehicle induction machine drives without a shaft encoder

Abstract

A new torque control scheme without a shaft encoder is proposed. The scheme is based on considering the effect of temperature on rotor and stator resistances in the conventional induction machine equivalent circuit. Although the model is appropriate for both the steady state and transient conditions, the steady state behavior of the induction machine is analyzed in this paper. The induction machine is tested over more than two thousand operating points. The tests are carried out with a variable voltage and variable frequency voltage source in both motor and generator regions. Parameter values of the proposed model are identified and the model is used to estimate speed of the induction machine from its body temperature, input power, and input current. The required voltage and frequency to obtain maximum efficiency in a particular speed and command torque is calculated using the new model. This had been done for the whole torque and speed plane and the results are accumulated in a look up table. Under all circumstances, the induction machine temperature is taken into consideration. High efficiency and speed sensorless operation are two main advantageous of the proposed control technique. >