# Review of Energy Management Systems in Microgrids
## 1 Introduction  
One of the most efficient ways to produce energy is through fossil fuels, which include coal, oil, and natural gas. Recent scientific research demonstrates that these energy sources have detrimental effects on human health and the environment in addition to their economic effects [1; 2; 3]. Along with these effects, because of different reasons such as increasing energy demand, increasing energy prices, energy source dependency, etc., scientists are investigating alternate energy resources. Renewable energy resources and distributed generation have historically been used to try to meet the needs of reducing the negative effects of electrical energy production on the environment, meeting the ever-increasing demand for electrical energy, and improving the quality, reliability, and stability of power systems [4; 5; 6]. Increasing the capacity of electrical networks and extending transmission lines to feed farther-off electrical loads raise the costs of producing electrical energy as well as transmission-distribution losses due to the growing electricity demand [7]. Distributed generation which mostly employs renewable resources like solar and wind power is a good opportunity to solve these problems. Microgrids, which are small-size power grids, are also proposed for the same purpose. A microgrid can employ conventional and renewable distributed energy resources. Microgrids can supply energy to local-regional loads or the main power grid with these resources. Therefore, nearby loads can receive electrical energy from energy sources that are dispersed throughout a given area. They can also run in islandmode (off-grid) or grid-connected (on-grid) mode. From these angles, microgrids provide many advantages for the future of power grids [8]. Microgrids containing renewable energy sources are used to reduce the annual electricity bill, energy purchased from the grid, and greenhouse gas emissions in the conventional power system. Microgrids can be used to increase the sustainability of electricity supply and minimize poverty in developing countries [9]. The large inertia moments of large power generators are crucial in suppressing oscillations in voltage and frequency that occur in traditional power systems. Compared to conventional generators, distributed generation units in microgrids are more unstable due to system oscillations in voltage and frequency because they are connected to the grid through power electronic converters [10]. To guarantee that microgrids run consistently, effectively, and in compliance with standards, a control system must be developed. Numerous problems, including voltage-frequency regulation, proper load sharing, synchronization with the main grid, control of the power flow between the microgrid and the main grid, and operating cost optimization, should be solved by this control system [11]. For the distributed energy resources that microgrids use as power sources to cooperate effectively, energy management is crucial. Efficient, safe, and intelligent use of distributed energy resources among microgrid components is important for power quality and supply-demand balance in the system. This can be achieved by using energy management systems in microgrids. Numerous approaches, including multi-agent systems, model predictive control, artificial intelligence techniques, meta-heuristic-based methods, stochastic and robust programming-based methods, and classical method-based approaches, are used in microgrid energy management systems [12]. A new class of electricity sources that provides balanced electrical energy generated by clean and environmentally friendly energy resources is microgrid power systems. Microgrids are also called multiple energy source systems or hybrid renewable energy systems. Two of the cleanest methods of generating electrical energy are solar photovoltaic (PV) systems and wind turbines, which are both widely used globally.