Optimal energy storage management in DC power networks

Micro grid technology has been attracting attention as a realization of local electricity production for local consumption. In a micro grid system, management of supply and demand is one of the most important issues because variability of renewable energies such as photovoltaic and wind power generations will cause a supply-demand imbalance. Management of supply and demand in direct current (DC) power networks is supposed to be more difficult in comparison with conventional methods for alternate current (AC) power networks. The reason why is that a delay in the conversion of DC to DC and AC to DC causes unintended power down in DC power networks without huge power supply such as grid power in AC power networks. In this paper, we propose an energy management method for DC power networks. A control system which realizes the proposed energy management consists of a two-layered structure. The first layer is a scheduling part which is responsible for deciding the long-period system behavior to reduce energy bills. The second layer is a supply-demand adjustment part which is responsible for maintaining instantaneous supply-demand balances for DC-driven devices. The effectiveness of the proposed method has been proven with some experiments using real equipment.