Selective active filtering for four-wire loads: Control and balance of split capacitor voltages

This paper presents a controller for the DC voltages on the split capacitor topology for a four-wire selective active filter. A simple model for the dynamics of the two capacitor voltages is derived under the assumption of time-scale separation between the dynamics of the inverter currents and the capacitor voltages. The controller proposed is based on physical principles and can be easily integrated with existing four-wire active filter controllers based on instantaneous reactive power (p-q) theory. Simulations and experimental results illustrate the benefits of the solution proposed.