Optimal harmonic injection in thyristor rectifier for power factor correction

An analysis of power factor (PF) improvement and harmonic optimisation schemes through study, modelling and hardware implementation is presented. Results show that PF is improved and harmonic distortion is reduced when the selected third harmonic current injection schemes are applied to a diode rectifier. Of the two schemes considered, scheme ´a´ with R-L-C components yields a better performance as compared to the scheme with R-C components only. Analysis is then extended to the controlled thyristor rectifier. It is found here that in addition to scheme ´a´, a compensating current phase shifter is required. Results show that for controlled rectifiers only the R-L-C scheme with the addition of a compensating current phase shifter and synchronisation (proposed scheme) reduce the input current harmonics significantly and PF is highly improved.