This paper presents a coalitional game for value sharing in energy communities (ECs). It is proved that the game is super-additive, and the grand coalition effectively increases the global payoff. It is also proved that the model is balanced and thus, it has a nonempty core. This means there always exists at least one value sharing mechanism that makes the grand coalition stable. Therefore, prosumers will always achieve lower bills if they join to form larger ECs. A counterexample is presented to demonstrate that the game is not convex and value sharing based on Shapley values does not necessarily ensure the stability of the coalition. To find a stabilizing value sharing mechanism that belongs to the core of the game, the worst-case excess minimization concept is applied. In this concept, however, size of the optimization problem increases exponentially with respect to the number of members in EC. To make the problem computationally tractable, the idea of clustering members based on their generation/load profiles and considering the same profile and share for members in the same cluster is proposed here. K-means algorithm is used for clustering prosumers' profiles. This way, the problem would have several redundant constraints that can be removed. The redundant constraints are identified and removed via the generalized Llewellyn's rules. Finally, value sharing in an apartment building in the southern part of Finland in the metropolitan area is studied to demonstrate effectiveness of the method.

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Continuous search for safety enhancements, reported events from the past and changes in the power system motivate studies on the impact of power systems in the safety of operations of nuclear power plants (NPP). The on-and off-site systems of an NPP have interactions with each other, but these are usually simulated with separate tools and with varying levels of detail.This paper builds on previous work in developing a cosimulation platform that connects the simulation of the thermomechanical and automation systems of an NPP with the simulation of the related electrical power systems, composed of the on-site grid and the off-site grid (transmission system). This co-simulation platform enables the integration of largescale NPP models and performance of fault-based simulations to evaluate the impacts of selected grid fault scenarios on NPP operations. This paper presents an overview of the simulation models, describes the tested fault scenarios that affect both onand off-site electrical grids, and offers a comparison between simulation results obtained with the co-simulation platform and simulations comprising only the electrical systems, which treat the NPP as a black-box.The presented results show the disturbance response at various system levels, allow comparison with alarms and protection function limits and assess where the co-simulation approach may be of benefit.