We consider the formulation of hybrid three-phase, three-sequence models of distribution systems and single-phase, three-sequence models of generation and transmission systems to compute the power flow solution. The term hybrid refers to formulations of modern power systems that mix electronic equipment such as HVDC links and that consider converter-connected loads and generators with conventional electro-mechanical elements such as for example synchronous generators and turbine governors. The target of hybrid formulations is to allow the simulation of the entire mixed power system. In this paper we specifically consider the computation of the power flow solution of hybrid power systems. We propose a systematic approach to correctly link different models and to compute the power flow solution with an acceptable accuracy level.