GRIDLAB-D is a power distribution system simulation and analysis tool first released in 2008 by the U.S. Department of Energy (DOE) at Pacific Northwest National Laboratory (PNNL). GRIDLAB-D is an agent-based simulator for distribution systems that integrates a range of objects / actors in the energy system, e.g. residential loads, climate / weather, energy storage, distributed generation, demand response, etc. The simulator is held together by a three-phase power flow, which runs at every time step.

 Reference: GRIDLAB-D