HYBRID FILTER FOR REDUCING DISTORTION IN A POWER SYSTEM

摘要

An apparatus (10) and method for reducing distortion currents present in an alternating current power system (12) supplying power to a load (16) includes a passive filter (26, 152) and an active filter (24, 150). In a first embodiment, the passive filter (26) is operably connected to the power system (12) across the load (16) by a switching device (30). The active filter (24) is then connected across the switching device (30) and operated to draw a current equal to the current through the passive filter (26). The active filter (24) and the passive filter (26) are thereby connected in series across the load (16). The active filter (24) is controlled to draw a fundamental frequency component and to provide distortion currents required by the load (16). In a second embodiment, the active filter (150) is connected in parallel with a first circuit (154), the parallel combination of which is connected in series with a second circuit (156) across the load (16).