Analysis of the fourth leg command of a three-phase active filter inverter

This paper presents a comparative analysis about the command strategies of the fourth leg of the inverter of a three-phase active power filter and why we chose the inverter structure of four branches. The aim is demonstrate the “controllability” of the four branch active filter by controlling the fourth leg. The aims of the different command strategies are both the elimination of the neutral current and to correct the line currents to sinusoidal shape.