Multifunctional energy management system for optimized network of microgrids considering battery degradation and load adjustment

In this paper, a multifunctional energy management system is proposed to operate a network of microgrids based on renewable energy with storage capability and no access to the main grid. The multifunctional framework allows the microgrids to operate separately in isolated mode, interconnected mode within the total network or hybrid mode with a partial network and isolated microgrids. In case of failure or loss of communication in one or more microgrids, the other unfaulty microgrids can continue operating in isolated mode or interconnected mode within the downsized network. In isolated mode, the local energy management system provides the discharge-charge of the battery storage and the load adjustment to maintain power balance and proper operation. In interconnected mode, a central energy management system provides optimal solutions for load adjustment, battery discharge-charge, in each microgrid, and power exchange between all microgrids within the network through solving an optimization problem. Furthermore, a combined energy management system is proposed for the hybrid mode operation. The nonlinear programming optimization problem is formulated by providing all constraints from the modeling of the microgrids network. The proposed framework for the energy management of a network of microgrids allows continuous operation of all microgrids despite failure to connect between some microgrids or desire to operate solely in the network for maintenance or specific applications. Simulation results are provided for multiple cases to demonstrate the effectiveness of the proposed multifunctional energy management system under different modes. It has been found that the load adjustment can be reduced by 93.72 % and 99.93 % in shedding and dumping, respectively, by operating the microgrids in a network compared to the isolated operation of each microgrid depending on the capacities of the microgrids. The multifunction energy management system allows operating all microgrids under different modes. Furthermore, it can keep the network of microgrids operational despite faults in one or more microgrids. The results show the effect of the strongest microgrid, with respect of excess power, compared to the other microgrids in the network.