PERFECTING OF THE UNIVERSAL INSTANTANEOUS POWER THEORY AND PRESENTATION OF LOAD PERFORMANCE INDEX
WANG Mao-hai ,LIU Hui-jin (School of Electrical Engineering, Wuhan University,Wuhan 430072, China)
A reasonable power theory should have not only distinct physical meanings, but also perfect mathematical characteristics. This paper approaches the universal instantaneous power theory(UIPT)from mathematical point of view: the mathematical expressions of active and reactive current are given, and the orthogonal relationship between them is validated. This paper also defines the correlation coefficient of load current and load voltage as load performance index, which is proved to be reasonable both in physical aspect and in mathematical aspect. The proposed load performance index is identical with the UIPT mentioned above. To make the UIPT and the proposed load performance index practically useful, this paper develops method to calculate active and reactive current with line voltages instead of phase voltages. This is a prominent merit especially for 3-phase-3-wire circuit in which the determination of phase voltages is a problem under dispute.