Unification and Evaluation of the Instantaneous Reactive Power Theories

The instantaneous reactive power (IRP) theory proposed by Akagi and his coauthors is widespread. When applied to a three-phase four-wire system, two types of IRP theories are available: the original and the modified IRP theory. However, there are ambiguities about which is right between the original and the modified theory and what is wrong. In this paper, a unified IRP theory is proposed, in which unequal resistances of transmission lines are taken into account and those ambiguities are clarified. The original IRP theory provides the spatial optimal solution when the neutral line has infinite resistance, and the modified IRP theory when the neutral line has zero resistance. The unified IRP theory proposed in this paper always provides the spatial optimal solution and includes the original and the modified IRP theory.