An improved three-level shunt active filter

A shunt active filter is capable of removing harmonic currents from the supply of commercial and industrial sites. This paper presents a novel method for generating the compensating current signal for an active filter that uses a three-level inverter to provide a fast transient response. It is shown that the active filter must be positioned downstream of the power factor correction capacitors for stable operation. A new compensating current technique, based on sinusoidal subtraction, together with the faster response of the three-level inverter produces a shunt active filter system that has superior performance compared to traditional two level systems.