OpSim is a test- and simulation-environment with applications ranging from developing prototype controllers to testing operative control software in the smart grid domain. OpSim is created by Fraunhofer IEE and University of Kassel and enables users to connect their software to simulated power systems, or test it in conjunction with other software. The power grid simulator of OpSim is capable of emulating large power systems with multiple voltage levels and substantial amounts of generators, storages and loads.
The core of OpSim is a flexible message bus architecture; it allows arbitrary co-simulations in which power system simulators, controllers and operative control software can be coupled together.