# Review of Energy Management Systems in Microgrids
## 1 Introduction
Hybridization of various energy sources aims to produce stable and sustainable electricity by providing maximum electricity generation capacity at the lowest possible cost for areas served by conventional electricity grids. Nevertheless, energy storage devices are required to guarantee energy sustainability because renewable energy resources are sporadic and dependent on weather [13]. To regulate the power flow between sources, loads, energy storage systems, and the main power grid with various characteristics within the microgrid, an energy management strategy, as illustrated in Figure 1, is necessary. Microgrids combine energy storage systems, renewable energy sources, and the grid and can operate in island mode or grid-connected mode. Microgrids must have efficient energy management in place to guarantee maximum energy efficiency. However, integrating renewable energy resources is made more difficult by the stochastic nature of wind and solar energy [14]. Thus, among the difficulties in energy management and microgrid optimization are arranging unpredictable operating conditions of distributed generation and guaranteeing economical and adaptable operation with a variety of resources. The microgrid's energy management system carries out several tasks, including tracking, evaluating, and projecting power generation based on the features of distributed generation systems, load consumption, energy market prices, and meteorological conditions. Energy management systems can optimize the microgrid with the help of these features. In the microgrid, if the power demand in the system is less than the power produced by resources, the excess power is stored in energy storage devices. If the demanded power is more than the produced power, the required power is met from energy storage devices, and in case of a connection to the grid, it will be drawn from the grid or transferred to the grid. To perform tasks such as determining the amount of power to be transferred, an effective energy management system must be established between the production,consumption, and storage systems. Thus, controllers can work in coordination with the demand from the load to achieve appropriate energy management [5]. For energy-efficient operation, energy management systems are crucial in the utility, industrial, commercial, and residential sectors. Energy management systems aim to minimize greenhouse gas emissions, optimize distributed energy resource planning, and reduce energy consumption. Monitoring and data analysis are made easier for energy management systems by their integration with a human-to-machine interface (HMI) and supervisory, control, and data acquisition (SCADA) system. It includes the weather forecast, load demand, power output from generation resources, and the current price of energy. The energy management systems make use of this data to maximize system performance at the distribution, transmission, and generating ends. Most microgrid energy management systems examined in the literature have centralized supervisory control architecture. However, because distributed energy resources are becoming more and more integrated into the power system, the centralized architecture is confronted with challenges related to high computational time, limited system scalability, and high instability in the event of failures. For this reason, a decentralized supervisory control architecture has gained more attention from researchers recently. The requirement for a constant two-way communication link between microgrid components and their synchronization, however, raises the cost of the system. Furthermore, it is necessary to optimize the cost of these communication systems' upgrades [15]. Energy management in microgrids is very important in real-world applications in utilities, industrial, commercial, and residential sectors for efficient energy operation. By using these energy management systems in daily life, they aim to optimize distributed generation resource planning, reduce energy consumption, and minimize greenhouse gas emissions.