A Hierarchical Energy Scheduling Framework of Microgrids With Hybrid Energy Storage Systems

The stochastic and intermittent nature of renewable energy resources (RERs) poses great challenges to the energy scheduling of microgrids. The hybrid energy storage system (HESS), such as a combination of the battery (BA) and ultracapacitor, is considered as an effective way to cope with such challenges. In this paper, a hierarchical energy scheduling framework is proposed for the microgrid with HESSs to optimize the operation under the uncertainty of RERs and loads. The framework consists of two stages of scheduling: hour-ahead scheduling and real-time scheduling. In hour-ahead scheduling, a deterministic optimization model is formulated to minimize the operation cost of microgrids, and to guarantee the operation safety. Subsequently, a decomposition-based method is presented to solve the proposed model. In real-time scheduling, a control strategy of HESSs is developed to accommodate the imbalanced power mainly due to the uncertainty of RERs and loads, while extending the lifetime of BAs. The methodology is tested on a seven-bus microgrid system. Simulation results validate the effectiveness of the formulated model and the developed strategy.