Distributed Active Filter Systems (DAFSs): 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 (AFUs) installed on the same location or different locations within the power system. Each individual AFU functions like a harmonic conductance to reduce voltage harmonics. A droop relationship between the harmonic conductance and the voltampere (VA) of the AFU is programmed into the controller of each unit, so multiple AFUs can share the workload of harmonic filtering without any communications. The slope of the droop is determined by the VA rating of the AFU 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 a computer simulation and laboratory test bench are provided to validate the functionalities of the proposed DAFS

I. Introduction

The proliferation of nonlinear loads in the power system has been growing in an unprecedented pace in recent years due to the advance of power electronics technologies. As a result, the harmonic pollution in the power system deteriorates significantly. Harmonic resonance, which results in severe voltage distortion, has been reported. Previous literatures propose the installation of active filter at the end of radial lines to damp the harmonic resonance [1]–[3]. However, depending on the magnitude of the damping provided by the active filter, the level of harmonic distortion may become worse at certain locations along the radial line. Multiple installations of active filters have been presented in [3], but real-time communications among various units are required to coordinate the operations.