The p-q theory and active current under non-sinusoidal conditions

This paper presents the study of the p-q theory introduced by Akagi in 1983, under non-sinusoidal currents and voltages. His theory introduces the concept of instantaneous active and reactive power in a stationary orthogonal coordinate system. Several authors have shown, however, that, this theory has several limitations. Of these, Czarnecki especially criticizes the active and reactive character of Akagi´s orthogonal currents, introducing his physical components of the non-sinusoidal current. The paper makes a comparison between the current components defined by Akagi by means of his classic p-q theory and by the 2^nd interpretation of the p-q theory, respectively, versus the current physical components introduced by Czarnecky (CPC theory). Through several case studies, the paper will delineate the domain of applicability of the p-q theory, for sinusoidal and non-sinusoidal voltages and currents, noting that even the 2^nd p-q theory definition is not valid when the grid voltage is non-sinusoidal.