The role of battery systems and expandable distribution networks for smarter grid

Renewable energies such as wind power and PV energy sources are valuable energy resources which can contribute to improvement of self-sufficiency rate of energy and can be used to reverse global warming. However, when there is a large amount of penetration of renewable energy generations into a grid, some problems will arise in the present distribution power network, due to instability of power output and large reverse power flow caused by the renewable energy generation. In researches on recent new electricity supply system, there is a way of thinking of local production for local consumption by the so-called micro-grid and smart-grid which supply the area demand by the area electric power resources, and several demonstrations have been performed also in Japan. From the viewpoint of local production for local and its consumption of electric power energy, a new type of expandable distribution network is proposed to meet regional expansion of the area's electricity demand and supply by the addition of electricity-cluster. The role and operation of battery energy storage system (BESS) in the expandable distribution networks are also discussed. Dynamical models of the expandable network and BESS for computer simulations are developed by MATLAB/Simulink, and the dynamic properties to maintain frequency and voltages in the cluster by appropriate operations of BESS are presented.