  A challenge in transmission-distribution coordination is how to quickly and
reliably coordinate Distributed Energy Resources (DERs) across large
multi-stakeholder Distribution Networks (DNs) to support the Transmission
Network (TN), while ensuring operational constraints continue to be met within
the DN. Here we propose a hierarchical feedback-based control architecture for
coordination of DERs in DNs, enabling the DN to quickly respond to power
set-point requests from the Transmission System Operator (TSO) while
maintaining local DN constraints. Our scheme allows for multiple
independently-managed areas within the DN to optimize their local resources
while coordinating to support the TN, and while maintaining data privacy; the
only required inter-area communication is between physically adjacent areas
within the DN control hierarchy. We conduct a rigorous stability analysis,
establishing intuitive conditions for closed-loop stability, and provide
detailed tuning recommendations. The proposal is validated via case studies on
multiple feeders, including IEEE-123 and IEEE-8500, using a custom MATLAB-based
application which integrates with OpenDSS. The simulation results show that the
proposed structure is highly scalable and can quickly coordinate DERs in
response to TSO commands, while responding to local disturbances within the DN
and maintaining DN operational limits.
