Sayyad Nojavan

Penetration of renewable energy sources (RESs) in the power system is increasing day by day all around the world. Generating clean energy, coping with environmental effects, and depleting fossil fuel sources are just some of motivation for utilizing RESs in the system. Be-sides all those advantages, RESs have disadvantages, such as volatile power output, which may affect power system performance negatively. Among different RESs, wind and solar en-ergy sources are considered the most promising sources, which are widely utilized in the cur-rent power system. To accommodate the current power system with the RESs and to over-come the disadvantages of these sources, the concept of microgrids (MGs) is developed, which are defined as a combination of controllable loads and distributed energy resources that can be utilized in grid-connected or islanded modes. In the grid-connected mode, the MG can exchange energy with the upstream grid, while in the remote area the isolated MGs can be utilized to supply the required load. Benefits of implementing MGs in the power system can be counted as reducing power-generating cost, reducing greenhouse gas emissions, and reducing energy losses. The MGs can be classified from different point of views. For example, according to operational frequency they are grouped as AC, DC, and hybrid AC/DC MGs. In another classification, as said before, MGs are divided in two groups, grid-connected and islanded. Based on the control strategy of the MGs, they are grouped as centralized and decentralized. Finally, by taking application of MGs into account, MGs can be classified as utility/military and residential/commercial/industrial. In the structure of any type of MGs, the battery storage systems can be implemented to cope with the volatile and uncertain power output of RES sources. The battery storage sys-tems store excessive generated energy by wind turbines and photovoltaic systems, and the stored energy can be used when the system encounters a lac