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.