Keywords: harmonic compensation, nonlinear loads, hysteresis control, dual buck topology, dual boost topology, buck and boost topology, voltage sector identifier, current polarity identifier, FACTS, switching strategies
A novel hysteresis switching strategy for harmonic compensation
A simple and novel control technique for harmonic current compensation is presented. For each 60° duration of line cycle, the three-phase controlled bridge can be considered as dual buck, buck and boost, or dual boost configuration depending on the grid voltage and injected current polarities, and that only two switches are controlled at high frequency at any instant of time. A three-phase diode bridge with R, R-L, or R-C loads has been considered as nonlinear loads. Harmonics currents have been extracted and used as reference current signal. A switching algorithm for injection of any type of harmonic current has been developed and constant frequency hysteresis current control is proposed. The magnitude of the injected current can be controlled to bring the harmonics at source side to a minimum. The simplicity of the control circuit and the reduction in switching losses with excellent dynamic performance are the salient features of this control technique.