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.
The installation of an energy storage system (ESS) is vital for the Micrgorid (MG) islanded operation to ensure the maintenance of demand-supply balance. Lithium-ion batteries (LIBs) are among the most commonly used ESS technologies for grid-based applications, which is used in this paper to constantly maintain the demand-supply balance in a residential MG. For this purpose, a novel frequency-based energy management scheme is proposed. It uses an LIB ESS to handle the primary frequency control and energy management during peak-load period, while the dispatchable distributed generators like microturbine and fuel cell supply the base load. The airconditioning TCLs consume a significant part of the residential load profile, especially during midsummer. Unlike TCLs that instantaneously use their generated cooling thermal energy to control indoor temperatures, the thermal energy storage systems (TESSs) can also store the thermal energy and use it later. In this paper, the TESSs are used instead of TCLs to reduce the power consumption of a residential Microgrid (MG) in islanded mode. By doing this, the required LIBESSs capacity is decreased 70% considerably than the case the TCLs are used for controlling the indoor temperatures. Also, replacing the ACs and EHPs with TESSs results in a 63.7% reduction in the total cost of electrical and thermal storage.
Summary
The supercapacitors (SCs) are suitable for short‐term fast power regulations, while the batteries are suitable for long‐term slow energy management of microgrid (MG). As SCs and batteries complement each other's deficiencies, the SC‐battery hybrid energy storage systems (SBHESS) have been commonly used for mixed applications of fast transient and slow long‐term power regulations. The SC reduces the stress of fast power variations on the battery, which prolongs its lifetime. However, it increases the cost of the energy storage in comparison to the case that battery is just used. Therefore, the drawback of SBHESS is its increased cost. The sizes of SC and its converter, which directly determine their costs, should be enough to handle primary frequency control (PFC) in the worst cases of shortage and surplus power generation that the MG ever experiences. In this paper, the potentials of Photovoltaic (PV) systems, smart LED lighting loads (SLEDLLs), and thermostatically controlled loads (TCLs) in PFC is used to decrease the participation share of SC in the PFC and hence decrease the sizes and costs of SC, and its converter. The simulation results show that with the coordination of SBHESS, SLEDLLs, PVs, and TCLs, the required sizes of SC and its converter are decreased by 64% and 50%, respectively. Also, for a 10‐year period operation, the total cost of SC and its converter is decreased by 51.5%.
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