The dissemination on a large scale of non-linear loads in recent times, has made trivial their presence and use by the generality of industrial and domestic consumers. This, plus the fact, that this type of electric loads consumes distorted currents which are harmful for the Power Quality of the electric system, has lead to high energy and monetary losses for all parts involved in the power distributing system. It’s estimated that problems associated with Power Quality cost the industry and commerce of the European Union more than € 150 billion a year.

This type of loads also provoke modifications on the voltage wave shape, because the current harmonics, when they pass by the characteristic impedance, cause harmonic voltage drops, thus changing the wave shape of voltage measure at the load terminals.

Fortunately, there are ways of dealing with this Power Quality problems. The Series Active Power Filters are one of the most interesting equipments to mitigate the effects of the voltage harmonics, generating compensation voltages that once inserted in the electric grid, cancel the harmonic content of the load voltage, ensuring that the voltage at the load has a wave shape close to a sinusoidal wave.

The Group of Energy and Power Electronics (GEPE) has been following closely the evolution of these type of solutions, and has been through the years developing projects to experiment different topologies options and control theories for these equipments. Together with the projects, GEPE has produced diverse literature on this subject (papers and dissertations) that document and complement the practical approach.