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 systems obtained using the decoupled harmonic power flow (DHPF) algorithm. In this algorithm, the interaction among the harmonic frequencies is assumed to be negligible and hence the calculations are separately performed for every harmonic order of interest. A detailed methodology is presented for harmonic analysis of distribution systems in the frequency domain, which calculates current and voltage high order harmonics, harmonic losses and total harmonic distortion of voltage. The standard backward/forward sweep method is used for solving the power flow problem at fundamental frequency. Furthermore, some practical and approximated models of network components in harmonic analysis are given. The performance of the DHPF approach is studied and evaluated on two standard test systems with nonlinear loads, the distorted IEEE 18-bus and IEEE 33-bus. Nonlinear loads are treated as harmonic current sources that inject harmonic currents into the system. The DHPF algorithm is verified by comparing its results with those generated by software tools for the analysis of transmission, distribution and industrial power systems (i.g. ETAP and PCFLO). Simulation results show the accuracy and efficiency of the applied procedure for solving the harmonic power flow problem.