Control scheme of hybrid active filter for power quality improvement

A control scheme of hybrid active filter with integrated series active filter and parallel passive filter for power quality improvement is presented. The system is capable of compensating the current and voltage harmonics and voltage sag in distribution system. The line current is controlled to be sinusoidal in phase with mains voltage and load terminal voltage is controlled to be fixed under a wide range of distorted line voltage. The power rating of inverter in the series active filter is reduced by comparing with that of pure active filter to suppress the harmonics. A series voltage compensator is used to improve the power quality of load terminal voltage. The control concept of hybrid active filter is analyzed with the experimental results in a scaled-down laboratory prototype to demonstrate the proposed control strategy.