Stochastic reserve scheduling of energy storage system in energy and reserve markets

•A joint energy and reserve market model considering uncertainties is proposed.•The proposed hourly reserve model of ESSs contains six reserve modes.•Multi-hour reserve model assures the availabilities of energy and reserve. Energy storage systems (ESSs) can be used to participate in both the energy and reserve markets to maximize their reserve benefits. In contrast to traditional thermal units, ESSs have three statuses: charging status, discharging status, and idling status. The energy-limited feature of ESSs makes it difficult to schedule the reserve in the joint energy and reserve markets. In this paper, a detailed energy and reserve model of ESSs is considered in the joint stochastic day-ahead unit commitment model. The main highlights of this paper are the reserve model of ESSs. Compared to existing studies, a proposed six-mode hourly power reserve model of ESSs can schedule more reserve amount to participate in the reserve market. The six reserve modes include more charging/discharging, less charging/discharging, and switch from another status to charging/discharging. Besides, multi-hour coupled reserve constraints are introduced to avoid ESSs failures to provide the reserves scheduled in the day-ahead market. Considering the uncertainty of demand and renewable generation, a scenario-based stochastic model is adopted to calculate both the energy and reserve costs of the whole system. Two different systems are used to discuss the benefits of the proposed reserve model and analysis on some crucial parameters.