Robust high-order repetitive control of an active filter using an odd-harmonic internal model

Shunt active power filters have proven to be an efficient means to compensate for the negative effects of nonlinear and reactive loads on the power quality of the electrical distribution network. In this context, the control objective is to achieve a power factor close to 1, as well as load current harmonics and reactive power compensation. A useful control strategy for this purpose is repetitive control. However, the performance of repetitive controllers is strongly affected by frequency variations of the involved signals. This work analyzes the effect of such variations and describes the architecture of an odd-harmonic, high-order repetitive controller specifically designed to obtain robust closed-loop performance against frequency variations that may occur in the electrical network.