Reference Current Computation for Active Power Filters by Running DFT Techniques

This paper analyzes the feasibility and convenience of applying the efficient discrete Fourier transform (DFT) techniques for the computation of reference currents in active power filters. Existing methods designed for this purpose rely on a high-pass filter in order to obtain the harmonic components of the load current to be filtered. Among these methods, the stationary reference frame (SRF) method reveals itself as the most accurate one because of its inherent immunity to distorted voltage conditions. In this paper, two different implementations of the running DFT, including their recursive and nonrecursive versions, are compared to the SRF approach in terms of steady-state performance, adequacy of transient response, and computational effort. In addition to simulation results, an experimental setup is designed to prove the advantages of resorting to the DFT. Conceptual similarities between both schemes are also stressed in this paper.