SPEED CONTROL OF INDUCTION MOTOR DRIVE WITH FRONT END ACTIVE (HPFC) CONVERTER

Abstract

Line-Commutated AC/DC converters using diode and thyristor bridges are mainly suffered disadvantages of unidirectional power flow and input waveforms are non-sinusoidal current, which therefore operate at very low power factor and harmonics, injected into the system also. Therefore creates problems of power quality. In recent decades, several new topologies have evolved, and were able to eliminate the drawbacks of line commutated converters and therefore designated as "front-end active converters" However, the building blocks of these new converters are devices of self-commutated semiconductor such as MOSFET, IGBT and GTO etc. which are intrinsically characterized by the switching frequency. ie the performance is highly dependent on the selection of the switching frequency. But with the high switching frequency, constraints dv and common - di mode voltage developments are the main problems. In addition, increasingly high power applications by the day, the two active lower level converters are in most cases. Multi-Level front converter that can absorb current harmonics generated by nonlinear loads connected to the same power distribution bus. In other words, the proposed active front end converter can function as an active power filter and at the same time as a converter. The speed control of an induction motor drive is mostly used in a vector control mode because of its ability to give a performance similar to that of a DC motor. These drives are supplied by a bridge rectifier diode of six pulses, which results in the injection of harmonics into the input current, which reduces the quality of the feed to the point of common coupling (PCC), it affecting consumers nearby. To have control over these harmonics can be reduced by using different techniques shaping active or passive wave. But here, the inverter fed induction motor drive effects the source current. Implementation of the improved power quality converter in front of the inverter by proper control so supply currents free form the harmonics and source currents and voltages are in same phase i.e, maintained unity power factor.