Conservative power theory application in shunt active power filtering under asymmetric voltage

This paper analyzes the current decomposition, in three-phase, three-wire systems, based on the Conservative Power Theory (CPT), and its application in the active filtering in non-sinusoidal and unbalanced conditions, by simulation as well as on an experimental workbench. The CPT current decomposition includes, beside the active, reactive and void components, an unbalanced component. This component makes possible for the active filter to compensate also the current unbalance, if desired. This is particularly interesting when the voltage is also unbalanced because of the load unbalance or not. In this case, the compensation will eliminate the voltage asymmetry due to the load current unbalance, but if the grid impedances are not equal on all the three phases, the compensated sinusoidal and balanced current will unavoidably produce asymmetric voltages in the PCC. Moreover, due to the CPT definition of the active current, the grid voltage asymmetry will produce a load current unbalance. The current decomposition based on the Conservative Power Theory was analyzed on various case studies, for a combination of typical nonlinear balanced and unbalanced industrial loads. First, the active filtering system was tested by simulation in the Matlab Simulink environment, and latter the validated system was further tested on an experimental workbench. Because of the Simulink model modular structure, the virtual filtering system was built equivalent to the experimental system.