Optimal sizing of smart grid storage management system in a microgrid

Development of microgrid (MG) technology is growing in low voltage networks, improving the power supply reliability and energy efficiency. Energy storage system (ESS) plays an important role in operation of MG to achieve higher flexibility and reliability. This paper presents a model for determining the optimal size of an ESS in MG. An expansion planning problem is proposed to consider the investment cost of ESS, as well as operating cost of the microgrid. By increasing the size of the storage system the investment cost linearly increases while the operating cost exponentially reduces. The objective is to find the optimal size of ESS in which the summation of storage system investment cost and MG operating cost is minimized. A practical model for ESS is utilized, which uses rectangular charging and trapezoidal discharging profiles. The optimal storage sizing problem is formulated as a mixed-integer programming (MIP) problem. Illustrative examples of a six-bus system are presented to show the efficiency of the proposed method.