In this paper, a photovoltaic (PV) generator is represented as a lumped-parameters network equivalent. This equivalent can be readily integrated into a power flow algorithm. The PV generator is initially modeled via its harmonic domain admittance matrix (HDAM). The HDAM is obtained by using the flexible harmonic domain (FHD) which permits to include frequency coupling. Reduction of the HDAM to fundamental power frequency quantities provides the lumped-parameters is-shaped circuit of the PV generator, amenable for power flow algorithm. It is demonstrated that multiple is-equivalents, emulating solar farms with distinct switching frequencies of the involved power electronics devices, can be integrated into the power flow solution algorithm. (c) 2021 Elsevier Ltd. All rights reserved.