With the increase of high non - linear loads and the inclusion of Distributed Energy Resources (DER) in the utility grid, power quality improvement has become a fundamental requirement in electrical systems, in order to minimize the harmonic distortion effects. This document presents an application of a shunt switching compensator based on instantaneous power theory in two different systems, in which power quality improvement is required. The first one is an offshore wind farm VSC (Voltage Source Converter) - based HVDC (High Voltage Direct Current) system, and the second one is a micro grid with high penetration of DER. These systems are validated using Matlab/Simpower and PSCAD/EMTDC, respectively. In both cases, an enhancement of the current THD (Total Harmonic Distortion) is observed, showing the advantages of active power filtering in super and micro grids.