A Strategy for Flexible Frequency Operation of Stand-Alone Multimicrogrids

Supply and demand balance is required to assure normal operation in microgrids. Especially, in stand-alone microgrid operation, load shedding is inevitable to meet the balance. In order to enhance the reliability of stand-alone microgrids, deployment of suitable sized controllable distributed generators is required, which results in an increase of investment cost. Therefore, a tradeoff between economical investment and reliable operation is required. In stand-alone multimicrogrid (MMG) system, the reliability can be improved by cooperative operation. However, solving the tradeoff is still a challenging problem. In this paper, an operation strategy is proposed for MMG systems where each microgrid has different frequency requirement according to load configurations to improve reliability from the economical viewpoint. A hierarchical energy management system is developed to implement the proposed strategy for MMGs operation. The validity of the proposed method is evaluated by using hardware-in-the-loop simulation. Test results showed the effectiveness for reducing load shedding and operation cost of MMG systems.