A practical approach of instantaneous power to control the unbalanced and nonsinusoidal three phase system

This paper propose a practical approach to the theory of instantaneous power in nonsinusoidal and unbalanced-three-phase systems. This approach is based on the symmetrical components theory (also called Fortescus transformations) in instantaneous state. General equations relating both the instantaneous powers and the symmetrical components in instantaneous state are developed. These general equations are fundamental in elucidating some important characteristics of the instantaneous powers and will be useful in understanding the control algorithms for the UPFC and the active filtering. A control strategy based on this approach is applied to the third generation flexible AC transmission system, UPFC and the active filtering. Theory and computer simulations using Simulink in Matlab environment demonstrate the practicality of the proposed approach.