PERFORMANCE ANALYSIS OF VECTOR CONTROLLED INDUCTION MOTOR DRIVE WITH DIFFERENT CONVERTERS

Abstract

Three Phase squirrel cage induction motor has been widely used for fixed speed applications because of its ruggedness, high efficiency at low cost, reliability, and minimum maintenance. A number of attempts have been made to implement three phase squirrel cage induction motors in variable speed applications. There are some control methods that allow the induction motor to work in variable speed drives, like, voltage control, frequency control and current control. The performance of these methods is excellent in steady state operation but it is unsatisfactory during transient period. Therefore, vector control technique was developed which merges the advantages of both the induction motor and dc motor and allows the induction motor to work in variable drives. In this investigation, the performance of vector controlled induction motor drive (VCIMD) is recorded under different operating conditions such as starting, reversal, step a change in speed and load perturbation using Simulink and power system toolboxes. A comparative study is done using four different speed controllers (Proportional Integral, Fuzzy Logic, Hybrid and Fuzzy Pre-compensated Proportional Integral) under stated operating conditions. Variable voltage variable frequency induction motor drives have a substantial potential of energy conservation in applications such as pumps, fans, elevators, etc. Variable frequency VCIMDs have an optimum operation in terms of energy consumption, when compared with Direct On-Line (DOL) started induction motors for a similar operation. A comparative study has been made based on the amount of electrical energy consumed by the VCIMD and by the direct on-line started induction motor under different operating conditions. Normally, VCIMD system feeds from converter-inverter arrangement, which suffers with the problem of harmonics in the supply current and poor power factor of the system. Some power quality improvement techniques are incorporated to improve the supply current waveform. To improve the power quality factors of VCIMD system, the ac-dc converter is fed through phase shifting transformers to realise multi-pulse converters.