Universal active power filters based on nine-leg converter

This paper proposed two universal active power filter (UAPF) topologies for reactive power and harmonic compensation. The proposed system is a combination of series and shunt active power filters. They are suitable to improve the harmonic distortion in the grid currents and a voltage compensation. The filters are composed of three three-phase converters resulting in nine legs. The first (configuration I) can operate with floating dc-link capacitor or an auxiliary DC source on the series filter and the second one (configuration II) uses a combination of two series filters and one shunt filter sharing a single dc-link. The complete control system, including the PWM techniques, is developed and a comparison between the configurations is done. Simulation and experimental results are shown for validation purposes.