  This paper presents a case study for utilizing behind-the-meter (BTM)
distributed energy resources (DERs) to provide grid services when controlled by
a DER Management System (DERMS). The testbed consists of a 5,000 buses
transient-stability (TS) real-time (RT) model, two 9,500 buses distribution
feeders from local utilities modeled in a distribution system simulator (DSS),
and hundreds of DERs. MQTT communication protocol is utilized to interface the
models in RT. Two main studies are carried. In the first, it is found that DERs
with frequency-watt droop response can help maintaining stability in the future
NYS grid in which thermal synchronous generators have been substituted by
renewable energy resources. In the second, results demonstrate that BTM DERs
can provide similar level of frequency regulation services expected from large
utility-scale generation.
