## 2 Background of Microgrids
### Historical Development of Microgrids  
Microgrid systems have a rich historical development that dates back to the early 20 th century. This part explores the evolution of microgrid technology from its inception to the establishment of early isolated systems. The Pearl Street Station, constructed by [PERSON] in 1882 in New York City, can be regarded as an early form of a centralized power station and a precursor to MGs. The station utilized direct current (DC) generators to provide electricity to customers within a limited radius. While not technically a microgrid, the Pearl Street Station laid the foundation for the development of localized energy systems. As electrification expanded to remote areas, isolated microgrid systems emerged as a solution to provide electricity to communities and industries beyond the reach of centralizedgrids. These isolated systems typically included a local power generation source, often based on fossil fuels, and a distribution network serving a specific area. Examples of early isolated MGs include systems established in remote mining operations, rural communities, and islands. Early microgrid systems faced several challenges and limitations. Limited generation capacity was a significant constraint, often relying on diesel generators or small-scale hydroelectric plants. Fuel availability and transportation logistics posed challenges in remote locations. Moreover, the lack of interconnectivity between MGs and the main grid limited their ability to share excess energy or receive backup power during outages. These limitations emphasized the need for technological advancements and grid interconnection to unlock the full potential of MGs [8, 48]. The background of MGs is closely tied to the evolution of the electric power industry. In the early days of electrification, power systems were small and isolated, serving specific communities or industrial sites. As the industry grew, power systems became larger and more interconnected, leading to the development of centralized power plants and transmission grids. This model of power generation and distribution has been the dominant paradigm for most of the 20 th century, but it has also presented a number of challenges. One of the primary challenges of centralized power systems is their vulnerability to disruptions. If a transmission line or substation is down, it can cause a widespread outage that affects thousands or even millions of people. In addition, centralized power systems are often inefficient, with significant energy losses during transmission and distribution. Furthermore, centralized power systems are often heavily reliant on fossil fuels, which can have significant environmental impacts. The creation of isolated microgrid systems in remote areas was driven by various motivations, including geographical limitations and the desire for energy self-sufficiency. Many remote areas, such as islands, mountainous regions, and sparsely populated rural communities, faced significant challenges in accessing electricity from centralized grids due to their geographical location. Extending transmission lines from distant power plants to these areas was often economically and technically impractical. As a result, establishing isolated microgrid systems became a viable solution to meet the energy needs of these communities. By generating electricity locally and distributing it within a limited radius, isolated MGs could overcome the geographical limitations and provide reliable power to the inhabitants. Another motivation for creating isolated microgrid systems was the desire for energy self-sufficiency. In some cases, communities or industries sought to reduce their dependence on external energy sources, such as imported fuels or the main power grid. Establishing MGs allowed them to generate electricity locally using available resources, which could be renewable or conventional, and have greater control over their energy supply.