It is difficult to forecast renewable energy resources due to their variability. High uncertainty of the resources increases the concern about the reliable operation of the electric power system. Storage devices have been considered a candidate to control variable energy resources, and most studies on storage devices are performed in the economic dispatch. Therefore, electric power adequacy may be an issue. In this paper, a new approach in the optimal power flow framework is proposed for

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... ng storage devices, and the feasibility and economic impact analyses are discussed. Index Terms-DC power flow, optimal power flow (OPF), power transfer distribution factor (PTDF), storage devices, variable energy resources.