Smart Hybrid AC/DC Microgrids

1Smart Hybrid AC/DC Microgrids: Structures and Technical Challenges

1.1 Introduction to Microgrids

1.1.1 Concept of Microgrids

“Microgrids” became jargon in the electrical engineering field at the beginning of the twenty‐first century. After nearly two decades of development, the core of this concept keeps expanding and growing along with the development of many other fields, such as power electronics and smart grids. In general, a microgrid refers to a less complex form of an electrical grid, consisting of power generation, energy storage, and consumption as well as essential interfaces. Its functions, on the other hand, entail many more differences than conventional grids [1], e.g. (i) it can work in grid‐connected or standalone operation modes; (ii) To the grid, it operates as a self‐controlled entity; (iii) it normally features an advanced control strategy to optimally regulate the intermittence from renewable energies, providing high reliability and high power quality; (iv) it is typically located near the users as well as the power generators in a distributed manner, providing high flexibility and cost‐effectiveness.

Another important concept closely related to microgrids is distributed generation (DG). DG mainly refers to power generation with distributed forms, differing from the traditional centralized power plant. DG technologies can use sources such as: (i) renewable energy resources such as wind, photovoltaic, micro‐hydro, biomass, geothermal, ocean wave, and tides; ...