A Lookup Table-Based Reference Flux Linkage Selection of Direct Torque Control Induction Motor Drive for Electric Vehicle Applications: An Offline Strategy

In recent years, countries worldwide have framed policies for faster adoption of electric vehicles. To meet the requirements of electric vehicles, research activities in academia as well as in industry have intensified. One of the significant areas of research is low-cost and high-efficiency electric drive for these vehicles, and their control over a wide range of operations. In this article, an electric vehicle drive with direct torque control of induction motor is presented. This article addresses the impact of reference flux linkage on the operation of induction motor for direct torque control over a wide speed range. A nonlinear equivalent circuit model of an induction motor is considered to obtain values of reference flux linkage. The method uses the nonlinear equivalent circuit parameters to do the offline calculation to determine the reference flux linkage, and a lookup table is generated. The proposed method does not need to develop the finite element analysis-based induction motor model to generate the lookup table. The obtained lookup table has two inputs: Reference speed and reference torque. Based on these two inputs, suitable reference flux linkage is selected from the lookup table. The proposed method calculates reference flux linkage taking into consideration the reference speed and torque as well as dc voltage. This lookup table is eventually implemented with the direct torque control algorithm. The proposed methodology for selecting reference flux linkage is compared with the variable flux technique, loss model-based technique, and the finite element analysis-based lookup table approach for various vehicle driving cycles. The comparison is made in terms of the drive cycle tracking response, dynamic, and steady-state performance. Besides, energy consumption and efficiency analysis are also discussed. The obtained experimental results confirm that the proposed method shows better performance above all aspects over a wide speed range.