A very useful observation made by Professor Andrei Ţugulea in mid 1980s allowed a new paradigm considering active and reactive power flow interpretation in three-phase circuits comprising at the same time nonlinear and unbalanced components. The article is intended to provide a deeper analysis, from this theory perspective, of a three-phase circuit with zero impedance neutral, which presents two different nonlinear and distorting loads powered through a supposedly balanced line. Symmetry, non-symmetry and residual (distortion) active and reactive powers are the appropriate quantity concepts defined by this theory capable to successfully take into account the nonlinearity and unbalance effects on active and reactive power circulation. Associated to these quantities, three normalized coefficients were introduced to allow a more direct depiction of the phenomena, namely symmetry, non-symmetry and distortion power factors. Original formulation of the theory was made for two balanced linear loads and a single unbalanced distorting one. The present work now considers a single balanced linear load (the power line) and two unbalanced nonlinear (distorting) loads, in a three-phase circuit with zero impedance neutral. Through PSpice simulation of various parameter circuits, all the possible instances regarding active and reactive powers flow directions are put demonstrated. To conclude, the obtained results are presented and interpreted.

Keywords: Three-phase circuits with neutral, Ţugulea theory, Nonlinear (distorting) load, Symmetry active power, Nonsymmetry active power, Residual (distortion) active power, Symmetry reactive power, Non-symmetry reactive power, Residual (distortion) reactive power, Circuit simulation