Soft computing based space vector modulation with direct torque control for pmsm servo drive

Abstract

The usage of electrical energy is inevitable in the current days. About two-third of electricity is utilized by motors of power industries worldwide. Electric motor, power electronics drive circuit, sensors and controllers are the major parts of a typical drive system. AC induction motors play a vital role in industrial applications. But higher energy losses and lower efficiency shrink the usage of AC induction motors in industries. The recent developments in permanent magnet (PM) material technology and the features of Permanent Magnet Synchronous Motor (PMSM) like high power density, simplicity, high efficiency and ease of maintenance lead to the replacement of conventional drives in power industries. PMSM is used in variable speed drives like electric vehicles, CNC machine tools, aeroplane and robot applications. Speed control of a machine is very important for electrical drive applications. Field control was replaced by Direct Torque Control (DTC) to control the speed and now DTC becomes the widely accepted technique for speed control of electrical drives. DTC is an efficient method to control torque and flux without changing the motor parameters and load. Efficiency of PMSM is due to its superior torque control, high torque at low speeds, and high speed sensitivity. The conventional DTC is not successful to control low speed conditions of Permanent Magnet Synchronous Motor. DTC with Space Vector Modulation (SVM) is adopted to achieve low speed control of PMSM. Space vector modulation is used to control the switching frequency. Torque, and flux ripples can be reduced by the selected output voltage vector in one sampling period. The occurrence of torque, flux and current ripple during steady state, leads to uncertainty and disturbances. For improving the response of this AC motor, intelligent control techniques are used. In this work, Fuzzy logic control(FLC), Adaptive Neuro Fuzzy Inference Systems (ANFIS) and Genetic Algorithms(GA) techniques are used for the speed control of servo motor drives to obtain high operating performance. Because of large torque ripples in low speed conditions of a PMSM when using the PItype speed controller in a conventional DTC, it is replaced by a fuzzy logic controller. newline