Insight into the Non-Symmetry and Residual Active and Reactive Power Flow in the case of Three-Phase Distorting Networks without Neutral

Abstract

The effects concerning the active and reactive power flow produced by nonlinear loads in three-phase networks without neutral are evaluated. The increasing large-scale employment of power semiconductor devices connected to the grid produces several important issues, like distortion in the voltage and current waveforms, but also parasitic active and reactive power injected into the grid by nonlinear and/or unbalanced loads, alike. A suitable theoretical approach to assess these effects was proposed in the 1980s by Professor Tugulea, who introduced the concepts of non-symmetry and residual (distorting) active and reactive powers, which provide a quantitative evaluation of these harmful effects and their influence across the power grid. Although its apparent conceptual simplicity, the difficulties posed by their actual calculation or practical measurement prevented a wider acceptance of the theory throughout scientific community. The present paper proposes several examples of the use of the abovementioned theoretical concepts, illustrated in the case of three-phase networks without neutral. The non-symmetry and residual active and reactive powers are numerically evaluated and plotted when a parameter of the test-circuits is variated. The obtained variation trends, reported for the first time to the authors' best knowledge, are interpreted and discussed as a conclusion of the present study.