PERFORMANCE EVALUATION & HARDWARE IMPLEMENTATION OF VARIOUS SPEED CONTROL TECHNIQUES FOR IM DRIVE

Abstract

Induction motor is extensively used in industry and in household applications due to numerous advantages, where it is operated at various speed and load torque. As a result, substantial amount of energy is consumed by induction motors. Hence, various efficient speed control techniques of induction motor drive need to be used for optimal use of energy. In this thesis, performance of various speed control techniques such as open loop and closed-loop V/f method, direct and indirect vector control method and direct torque control method of three phase induction motor drive is examined using Simulation and Experimental results. The goal of this study is to identify various advantages and disadvantages of each speed control technique. Simulation of scalar speed control method, vector control method and direct torque control method is performed in MATLAB Simulink and their performance is analyzed under various operating condition. The hardware implementation of open-loop and closed-loop V/f method is performed to test the performance of these method in real world. These methods are implemented on laboratory prototype using dSPACE DS1104 on a 3Hp, 415V, 50Hz Induction Motor. The performance of scalar technique is also observed using real-time Full Spectrum Simulator (FSS) and it is compared with the MATLAB simulation results to study its performance using two different simulation tool. FSS is advanced easily configurable controller which has a capability of performing offline and real-time simulation. It is also having hardware in loop capability which enable us to test new power electronic systems. iv

It is found that open-loop V/f system is very easy to implement and its response is satisfactory when precise speed control is not required whereas closed-loop V/f system provides precise speed control. The response of vector control method is fast as compared to scalar control method and it also provides performance like separately excited dc motor thus we can control flux and torque independently. Direct torque control method is very advance speed control technique and its performance is superior than all other methods and provides independent control of flux and torque like vector control. The disadvantage of vector control method and direct torque control is that they are totally dependent on voltage, current and speed feedback signals which makes the system complex and expensive. The experimental results of both scalar control techniques compared with the simulation results and it is observed that the experimental results almost match with the corresponding simulation results.