The design of advanced control systems to optimize the overall performance of parabolic trough collectors solar plants with direct steam generation is today a high-priority line of research. This paper presents the main development guidelines for dynamic models for use in simulation and control system design for such plants. The models are based in the ThermoFluid thermo-hydraulic modelling framework, developed with the Modelica object oriented modelling language. The paper focusses on the DISS experimental solar plant, located at the Plataforma Solar de Almería-CIEMAT (South-East Spain). The main plant operating modes are summarized, as well as the principal components modelled and modelling assumptions. Simulation results of a representative real experiment are shown, in which the values predicted by the model are compared to the real measurements and discussed.