Nonlinear control of single-phase shunt active power filters with theoretical analysis via singular perturbation

This work addresses the problem of controlling single-phase shunt active power filter (APF) in presence of nonlinear loads. The aim of control is twofold: (i) compensation of the current harmonics and the reactive power absorbed by the nonlinear load; (ii) guaranteeing a regulated DC bus voltage of the converter. The considered problem is dealt with using a singular perturbation approach that involves two loops in cascade. An inner-loop is designed, using the nonlinear proportional integral controller, to cope with the compensation issue and an outer-loop is designed to regulate the DC bus voltage of the converter. In this paper the nonlinear proportional integral controller is developed using the singular perturbation technique where two timescale motions are artificially induced in the closed-loop system. A detailed analysis of the stability control system is presented and the controller performances are illustrated by simulation in Matlab/Simulink environment.