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