Design and Fabrication of Front End Converter for Unity Power Factor

Abstract

A three-phase front-end rectifier is a line side converter that converts ac to dc voltage. The major drawback of this scheme is the injection of harmonics and poor power factor at line side due to use of thyristors and diodes. Hence, it is necessary to improve the power quality so that the system becomes more efficient. If power quality is not maintained then there are undesirable effects at both input and load sides. At input side if power factor is maintained at unity then for required load demand, the input KVA needed is less and hence, size of equipments needed would also be reduced and false triggering of IGBTs can also be avoided as shape of waveform will not be distorted one. Moreover, at output side due to improved power quality, the life of insulation increases and hence, chances of insulation failure are very less. This operation of maintaining unity power factor can be fulfilled by proposed scheme. Sine Triangular pulse width modulation technique is used to generate the gating pulses of the IGBT. The control strategy for three phase front - end converter consists of inner current - loop and outer voltage - loop. The power circuit of front-end converter with closed loop control is simulated in MATLAB for various steady state, transient and dynamic conditions. The proposed converter operates in forward power flow as well as in reverse power flow conditions. It is found that unity power factor is obtained for steady state as well as all dynamic and transient conditions. The proposed converter operates in forward power flow as well as in reverse power flow conditions. It is found that unity power factor is obtained for different load conditions.