Power flow in radial distribution systems in the presence of harmonics

Abstract

This paper presents the results of power flow calculations in the presence of harmonics in radial distribution systemsobtained using the decoupled harmonic power flow (DHPF) algorithm. In this algorithm, the interaction among the harmonicfrequencies is assumed to be negligible and hence the calculations are separately performed for every harmonic order of interest. Adetailed methodology for calculating current and voltage high order harmonics, harmonic losses and total harmonic distortion ofvoltage of the electrical distribution networks in the frequency domain is presented. The standard backward/forward sweep method isused for solving the power flow problem at the fundamental frequency. Furthermore, some practical and approximated models ofnetwork components in harmonic analysis are given. The performance of the DHPF approach is studied and evaluated on two standardtest systems with nonlinear loads, the distorted IEEE 18-bus and IEEE 33-bus. Nonlinear loads are treated as harmonic current sourcesthat inject harmonic currents into the system. The DHPF algorithm is verified by comparing its results with those generated bysoftware tools for the analysis of transmission, distribution and industrial power systems (i.g. ETAP and PCFLO). Simulation resultsshow the accuracy and efficiency of the applied procedure for solving the harmonic power flow problem.