Active filter control methods based on different power theories

A few different power theories are presented and used in the control strategies of the shunt active filter in case of the unsymmetrical supply voltage system. The time responses of the currents, instantaneous powers and losses, obtained by the simulation, are shown and compared. Although for the symmetrical voltage system with only the fundamental harmonic, different power theories provide effectively the same results, those may differ substantially for unsymmetrical supply systems with harmonics. The results, summarised in the table, show that the applied power theories influence substantially the basic performance criteria: the shapes of the supply currents, instantaneous powers, and losses. With regard to the purpose of the use of a device for power quality improvement an appropriate control strategy must be implemented.