A Real-Time T&D Co-Simulation Platform for Testing Grid Services of Distributed Energy Resources

This paper develops a real-time (RT) transmission and distribution (T&D) co-simulation platform for testing distributed energy resources management system (DERMS) algorithms. The platform consists of a transmission system modeled within a real-time transient-stability type environment interfaced to an active distribution network modeled within a fundamental frequency phasor-domain platform. The data exchange and time synchronization between the T&D models has been established via MQTT communication protocol, enabling the platform to communicate with a large number of DER models in real-time. The developed platform is generic in the sense that it can integrate an arbitrarily sized transient stability-type model of a transmission system with an arbitrarily sized fundamental frequency phasor-domain model of a distribution system. The platform does not impose an inherent limit on the size of the T&D models, and the size is limited by the computational capability of the simulation computer. This feature enables utilizing the platform for simulation studies of large-scale T&D systems. Furthermore, the developed platform enables both off-line and real-time simulations, extending its application from off-line planning-type studies to real-time operation-type and hardware-in-the-loop (HIL) studies. The paper demonstrates the application of the developed platform in a large-scale case study utilizing behind-the-meter (BTM) DERs to provide grid services when controlled by a DERMS. By including the propagation of dynamics between the simulation domains, realistic DER models, and typical communication protocols that are used in the field, the proposed platform enables the testing of DERMS algorithms in a close to real environment, replicating a wide range of power system phenomena that highlight the impact of a DERMS in an actual power system.