Simulink /modelsimco-simulation of direct torque control for induction motors

Abstract

This project presents a generic model of a direct torque controller (DTC) for induction machines (IMs) using field programmable gate array (FPGA). The DTC performance is significantly improved by the use of FPGA, which can execute the DTC algorithm at higher sampling frequency. This model is developed in order to reduce the sampling period to a point where torque ripple is minimal, while maintaining the classical DTC control structure. To get simpler implementation and fast computation, minimizing calculation errors and consuming hardware resource usage, three methods were introduced: i) two´s complement fixed-point format and a variable word-size approach was followed, ii) the modified non-restoring method to calculate complicated square root operation of stator flux and iii) a new sector analysis method. The design of the FPGA-based DTC for IMs is presented. Firstly, a novel DTC architecture was designed. Secondly, very-high-speed integrated circuit hardware description language (VHDL) is adopted to describe the behavior of the control algorithms. Finally, to evaluate the effectiveness and correctness of the proposed DTC, a co-simulation work performed by Matlab/Simulink and Modelsim is conducted. The simulation results will be discussed.