HYBRID-ACTIVE FILTERING OF HARMONIC CURRENTS IN POWER-SYSTEMS

Use of nonlinear loads and devices in power systems is expected to gro w rapidly. Examples are thyristor-controlled inductors for FACTS, conv erters for HVDC transmission and large adjustable speed drives. All of these loads inject harmonic currents into the power system. A novel h ybrid filter topology and its control, to prevent such harmonic curren ts from entering the power system, are presented in this paper. Analys is shows that in the proposed filter, the power electronic converter, required to generate harmonic currents for compensation, has a rating of only 9% when compared to the converter rating in an active filter a nd approximately one-half of that in a series-hybrid filter discussed in the literature. The proposed topology enables practical implementat ion of active harmonic current filters. The control of this filter und er transient conditions such as start-up and during steady state is de monstrated by means of simulations. Results from a scaled-down hardwar e prototype are presented to verify the simulations.