Control Methods and Compensation Characteristics of a Series Active Filter for the Neutral Conductor

Abstract

As a large number of electronic products such as personal computers are now connected to power distribution lines in commercial buildings, the serious problems such as voltage distortion on utility outlets and excessive neutral current on the distribution lines have arisen. This paper shows control methods and compensation characteristics of a series active filter connected to the neutral conductor. The distinctive functions of the proposed active filter are the mitigation of 3rd-harmonic voltage and reduction of neutral current in a three-phase four-wire distribution system. The required kVA rating of the proposed active filter is less than 10% of that of the harmonic producing loads. A control method of the dc capacitor voltage on the active filter circuit is also described. It is clarified through experiments that one of those two functions of the active filter can be realized selectively and the dc capacitor voltage of the active filter can be regulated to a desired value.