An extension to definition of apparent power for multiphase systems in non-sinusoidal conditions

摘要

The generalized definition of apparent power for multiphase systems in non-sinusoidal conditions isnextended in this paper. The meaning of apparent power is still a matter of discussion. The apparent powerndefinition for unbalanced three-phase systems is in two schools of thought. The first school is based on a purentheoretical approach and the second is related to the IEEE 1459–2000 standard, which is based on practicalnconcept. Both approaches define the apparent power as the maximum active power that can be delivered tonthe load for unchanged load equivalent voltages and currents. This paper at first, reviews the theoreticalnapproach of apparent power definition for three-phase unbalanced systems. Then this definition is extendednusing a vector space for multiphase power systems. This extension of the generalized definition considers ansystem which not only could be unbalanced but also could include non-sinusoidal voltage and currentnwaveforms. It also considers unequal line resistances. An example is presented which compares the resultsnobtained using this method with the results of the IEEE approach. A three-phase unbalanced non-sinusoidalnsystem in which a rectifying diode is employed in one of the phases is also used to further evaluatenperformance of different power definitions under study. By using an exact model to define the apparentnpower, the proposed extended definition provides accurate results. Copyright # 2010 John Wiley & Sons,nLtd.