A Novel and Optimal Battery Sizing Procedure Based on MG Frequency Security Criterion Using Coordinated Application of BESS, LED Lighting Loads, and Photovoltaic Systems

Abstract

This paper proposes a novel and optimal battery sizing procedure for the primary frequency control (PFC) of islanded microgrid (MG). The Battery Energy Storage System (BESS), Photovoltaic (PV) systems and LED Lighting Loads (LEDLLs) are coordinated to quickly intercept frequency deviation in the stage of PFC. The PVs decrease their power generation in the case of surplus of power generation. The LEDLLs decrease their power consumption in the case of power shortage. The BESS participates in PFC in both cases by injecting/absorbing power. Some batteries with overloading characteristics are capable of fast discharge/charge for a short period, which can be used to reduce the required battery size for PFC application. The conventional overloading characteristics is based on constant power discharge/charge, but the BESS power varies in response to frequency deviation. To overcome this problem, a modified overloading characteristic is presented based on variable power discharge/charge, which is used to propose a battery sizing algorithm. The Genetic Algorithm is used to optimally determine the frequency controllers' coefficients of the BESS, PVs and LEDLLs to minimize the required battery size while maintaining the MG frequency within safe operational limits. The proposed battery sizing procedure is evaluated on the CIGRE low voltage benchmark system using simulation in MATLAB/Simulink software. The results show that beside the overloading characteristics of the battery, the participation of PVs and LEDLLs in PFC also reduces the required battery size, because their participation reduces the share of BESS participation in PFC.

A Life Cycle-Cost Analysis of Li-ion and Lead-Acid BESSs and Their Actively Hybridized ESSs With Supercapacitors for Islanded Microgrid Applications

“…7 shows the MG network under study, which consists of a 0.4 kV distribution feeder connected to a 20 kV distribution network through a transformer. The network is the CIGRE distribution test system [4]. The MG contains a Solid-Oxide Fuel Cell (SOFC), a Microturbine (MT), a Diesel Generator (DEG), an ESS and two PV systems.…”

“…Based on statistical data of [4], the most severe contingency that the MG may experiences is 20 kW power shortage after an unplanned islanding. The SOFC and MT model for frequency regulation studies can be found in [39] while the DEG model is adopted from model which is presented in [40].…”

“…For longer durations, the same procedure, which is presented for one day energy management, can be used. The data of MG load profile is not available in [4], [41]. Therefore, the proposed profile of MG load in the mid-summer, which is shown in Fig.…”

“…In case of disturbances or failure in the main grid, the MG shifts its operation to islanded mode to ensure system stability. In the islanded mode, the MG may suffer from the imbalance between the demand and supply [4], and as the capacity of DGs is limited, they may not be able to supply the loads during some periods. Therefore, the primary concern is to meet demand by available resources [5].…”

“…In a standalone MG, the Lead-Acid batteries (LABs) are used for energy management and compensating supply-demand mismatch [12], [13]. The authors of [4], [14] investigated the application of LIB/LAB ESSs (LIBESS/LABESS) for frequency regulation of islanded MGs, respectively. In various studies, it has been stated that fast power regulations and high-power applications like frequency regulation shorten the life of LIBs and LABs [15], [16].…”