A flying-capacitor-based multilevel shunt active power filter for power quality improvement under severe operating conditions

A Shunt Active Power Filter (SAPF) based on the multilevel flying-capacitor topology is used for a three-phase four wire power distribution networks. The compensator consists of three active legs, each having three cells, and a neutral connection at the mid-point of a DC capacitor leg. A new control method for adjusting the current zero sequence is presented in this work. Combined with the known instantaneous reactive power theory, this proposed control strategy is applied to the active filter the inverter to achieve a perfect compensation for harmonics and reactive power when the load currents are non-sinusoidal and severely unbalanced.