This paper presents the open-source implementation in Modelica of the generic photovoltaics and wind turbine generator models introduced by the Western Electricity Coordinating Counsil (WECC) Renewable Energy Modeling Task Force. These dynamic models have been designed to be easily understandable and reusable by adopting the same decomposition as in the original WECC reports. It uses as much as possible existing Modelica Standard Library blocks and extends common parts whenever possible. The simulation results obtained with OpenModelica 1 and Dynaωo 2 -an hybrid C++/Modelica open source suite of simulation tools for power systems -have been successfully validated against different reference tools.