New Structure for Three Phase Four Wires Hybrid Active Filters

This paper presents a new structure for three phase four wires hybrid active power filters (APF). The main point with regard to other published structures consists of the connection of neutral wire to negative of DC bus in the inverter, thus avoiding the need of split capacitors at the DC bus. A particular control of voltage at the passive section of the filter allows the use of low voltage at the DC bus and provides a symmetry between t_on and t_off in the current controller. The paper includes a general discussion of the new structure and presents the control method for such a structure. Simulation and experimental results are given to show the behaviour of the system, used for harmonics cancellation