Optimal Sizing of Energy Storage System in a Micro Grid Using the Mixed Integer Linear Programming
INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH N.Ghaffarzadeh et al
Battery, as an energy storage system, plays an important role in operation of micro-grids (MG). This paper presents a new analytical cost-based approach to optimal sizing of battery energy storage systems (BESS) to reduce the operational and total costs of MGs. To do so, a unit commitment problem must be solved to obtain the optimal schedule of units, and then the proposed sizing approach will be applied. The objective function of this problem consists of different operational costs such as
... l costs such as energy production, operational and maintenance, startup and shutdown, emission, fuel costs, maintenance of spinning reserve and battery, which is one of the advantages of this paper. Furthermore, this paper studies a perfect set of operational constraints including, generating power limits, load demand balance, minimum up-time, minimum down-time, ramp rate capabilities, spinning reserve requirement and BESS operational constraints; that is the other advantage of the proposed method. The problem is formulated as a mixed integer linear programming (MILP) solved by the CPLEX solver in General Algebraic Model System (GAMS) software. Finally, to show the impact of the optimal size of BESS on the operational costs of MG, three different scenarios will be considered and compared with each other. The results show that the optimal size of the BESS exist and operational and total costs are minimum in the optimal case. As well as, output results compared by the other solvers such as MOSEK, LINDO confirmed the obtained results. Nomenclature t WT R c Certain radiation point that usually is set to 150 W/ . INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH N.Ghaffarzadeh et al., Vol.7, No.4, 2017 2005 r PV P The rated power of PV system [kW]. t MT f Cost function of micro turbine at time t. t MT P Power generated by micro turbine at time t [kW]. 01 , bb Micro turbine cost function coefficients. t FC f Cost function of fuel cell at time t. t FC P Power generated by fuel cell at time t [kW]. 01 , cc Fuel cell cost function coefficients. t dis W Energy produced by diesel generator at time t [kWh]. t dis P Power generated by diesel generator at time t [kW]. dis Diesel generator efficiency. t dis MT FC dis RU RU RU Maximum ramps up limit of diesel generator, MT and, FC, respectively. , , MT FC dis RD RD RD Maximum ramps down limit of diesel generator, MT and, FC, respectively. t BSr BESS reserve at time t [kW]. dis Coefficient of the piecewise linear approximation of diesel generator cost function.