  The establishment of a single European day-ahead market has accomplished the
integration of the regional day-ahead markets. However, the reserves provision
and activation remain an exclusive responsibility of regional operators. This
limited spatial coordination and the sequential market structure hinder the
efficient utilization of flexible generation and transmission, since their
capacities have to be ex-ante allocated between energy and reserves. To promote
reserve exchange, recent work has proposed a preemptive model that defines the
optimal inter-area transmission capacities for energy and reserves reducing the
expected system cost. This decision-support tool, formulated as a stochastic
bilevel program, respects the current architecture but does not suggest
area-specific costs that guarantee sufficient incentives for all areas to
accept the proposed solution. To this end, we formulate a preemptive model in a
framework that allows the application of coalitional game theory methods to
obtain a stable benefit allocation, i.e., an outcome immune to coalitional
deviations ensuring willingness of all areas to coordinate. We show that
benefit allocation mechanisms can be formulated either at the day-ahead or the
real-time stages, in order to distribute the expected or the scenario-specific
benefits, respectively. For both games, the proposed benefits achieve minimal
stability violation, while allowing for a tractable computation with limited
queries to the bilevel program. Our case studies, based on an illustrative and
a more realistic test case, compare our method with well-studied benefit
allocations, namely, the Shapley value and the nucleolus. We show that our
method performs better in stability, tractability, and fairness, which would
potentially be dictated by a criterion chosen by the regulator.
