Intelligent Harmonic Suppressor by Adaptive Fuzzy Controller for PEC9 Inverter under Unknown Nonlinear Loads

The presence of nonlinear loads challenges the power quality regulation in stand-alone and grid-connected converters. Employing bulky passive or active filters is common to filter out the harmonics; but this is a costly solution. In this paper, an Intelligent Harmonic Suppressor (IHS) using fuzzy control theory and Second Order Band Pass Filter (SOBPF) is proposed to mitigate the harmonics caused by unknown nonlinear loads in a stand-alone nine-level Packed E-Cell (PEC9) inverter. PEC9 is a promising multilevel topology which can generate a quasi-sinusoidal voltage waveform only by a single dc source. In the proposed IHS technique, PEC9 is forced by the fuzzy controller to track the desired current reference that is provided by an adaptive control law based on the load impedance. Simulation results verify that since the undesired harmonics emerge in the measured signals applied to the control loop, using SOBPF before the fuzzy control inputs notably reduces THD while the references for the load current and the auxiliary dc capacitors voltages are accurately tracked.