Distributed active filter systems (DAFS): a new approach to power system harmonics

This paper proposes a distributed active filter system (DAFS) for alleviating the harmonic distortion of power systems. The proposed DAFS consists of multiple active filter units installed on the same location or different locations within the power system. The active filter units of the proposed DAFS can cooperate, without any communication among them, to reduce the voltage harmonic distortion of the power lines. Each individual active filter unit functions like a harmonic conductance to reduce voltage harmonics. A droop relationship between the harmonic conductance and the volt-ampere of the active filter unit is programmed into the controller of each unit so multiple active filter units can share the workload of harmonic filtering. The slope of the droop is determined by the volt-ampere rating of the active filter unit in order to distribute the harmonic filtering workload in proportion to the rated capacity of each unit. The principle of operation is explained in this paper and test results based on computer simulation and laboratory test bench are provided to validate the functionalities of the proposed DAFS.