Nowadays, the traditional role of distribution grids as unidirectional passive structures with foreseeable loads is changing. They are becoming more complex and require more elaborate control. Conventional load flow methods, such as the Newton-Raphson, fast decoupled, and DC power flow, are widely applied on the transmission level but may show poor performance in distribution systems. This study aims to reveal, which power flow models and methods would be most suitable for distribution grids. First, an extensive literature survey of existing power flow models and solution techniques was performed. Then, a new classification scheme for the surveyed methods was proposed. Finally, common power flow methods were compared on three distribution systems, in practically important testing situations.