Adaptive learning based current control of active filters needless to detect current harmonics

This paper proposes a new current control method suitable for an active power filter (AF). It requires only detecting the source current. It requires neither detecting AF output current nor extracting a harmonic component from the source current Thus, the current control system can be greatly simplified compared to conventional load current detection AF. This paper introduces an adaptive digital filter (ADF) with a synchronized filtered-x (SFX) algorithm. An SFX-ADF based current controller exhibits high gains only at fundamental and harmonic frequencies that the load current contains. It automatically adjusts its transfer function to minimize the mean-square error. The proportional controller is also used to improve the dynamic performance of the current control system. Simulation and experimental results demonstrate that almost the same excellent filtering performance can be achieved as conventional load current detection AF.