Hybrid series active/parallel passive power line conditioner with controlled harmonic injection

摘要

A power line conditioner includes an active filter coupled, in series, and a passive filter coupled, in parallel, to a three-phase power distribution network. The three-phase power distribution network includes a voltage source that induces three-phase input currents at a first end of the three-phase power distribution network. A load, circulating three-phase load currents, is positioned at a second end of the three-phase power distribution network. The active filter controller of the invention uses synchronous transformations to identify selected harmonic reference components corresponding to individual harmonics of the three-phase load currents. The selected harmonic reference components are multiplied by a predetermined factor corresponding to a permissible percentage of the individual harmonics that may be injected into the supply voltage. This results in active filter reference signal components that are applied to the active filter. In response to the active filter reference signal components, the active filter injects a permissible percentage of harmonics into the supply voltage so as to reduce the voltage distortion at the passive filter. By reducing voltage distortion, the controlled injection of harmonics into the supply allows for a simplified passive filter design. Consequently, the passive filter may be implemented as a power factor correction capacitor.