Simulation of source current harmonic elimination technique using phase shifting transformer

This paper presents design of phase shifting transformer to reduce source current harmonic generated by using of variable speed drive (VSD) in textile industry. Nine VSDs are used in a stenter machine of a selected textile industry. Each of these VSD generates source current total harmonic distortion (THD) in range of 43.91% to 50.34%, which contains all odd order harmonics except the triplen ones. The first method to reduce this source current harmonic is by using arrangement of three phase shifting transformers, which requires one Yy three-phase winding connection to produce 0 degrees phase shifting, one Yz((+)) three-phase winding connection to produce 20 degrees phase shifting and one Yz((-)) three-phase winding connection to produce -20 degrees phase shifting. The second method is by using arrangement of nine phase shifting transformers, which requires one Yy three-phase winding connection with 0 degrees phase shifting, four Yz((+)) three-phase winding connections with 6.67 degrees, 13.34 degrees, 20 degrees and 26.67 degrees phase shifting respectively and four Yz((-)) three-phase winding connections with -6.67 degrees, -13.34 degrees, - 20 degrees and -26.67 degrees phase shifting respectively. Simulation results using MATLAB SIMULINK show that source current THD successfully reduced to 1.99% and 1.74% respectively when arrangements of three phase shifting transformers and nine phase shifting transformers are used.