TSO-DSO Operational Planning Coordination through “l1-Proximal”
Surrogate Lagrangian Relaxation
Abstract
The proliferation of distributed energy resources (DERs), located at the
Distribution System Operator (DSO) level, bring new opportunities as
well as new challenges to the operations within the grid, specifically,
when it comes to the interaction with the Transmission System Operator
(TSO). To enable interoperability, while ensuring higher flexibility and
cost-efficiency, DSOs and the TSO need to be efficiently coordinated.
Difficulties behind creating such TSO-DSO coordination include the
combinatorial nature of the operational planning problem involved at the
transmission level as well as the nonlinearity of AC power flow within
both systems. These considerations significantly increase the complexity
even under the deterministic setting. In this paper, a deterministic
TSO-DSO operational planning coordination problem is considered and a
novel decomposition and coordination approach is developed. Within the
new method, the problem is decomposed into TSO and DSO subproblems,
which are efficiently coordinated by updating Lagrangian multipliers.
The nonlinearities at the TSO level caused by AC power flow constraints
are resolved through a dynamic linearization while guaranteeing
feasibility through “l1-proximal” terms. Numerical results based on
the coordination of the 118-bus TSO system with up to 32 DSO 34-bus
systems indicate that the method efficiently overcomes the computational
difficulties of the problem.