Introduction to Grid-Forming Inverters

Abstract

In today’s electric power networks, unconventional energy resources, such as wind and solar (among others), and energy storage devices, such as batteries, are rapidly becoming more prominent. Small roof-top systems (a few kW) to large-scale stems (100–1,000 MW) are all connected to the main grid, both internally and directly to the high-voltage transmission network. Many of these new resources, rather than spinning electromechanical machinery, are coupled to a power source via power semiconductor converters, which is vital for our needs. Inverter-based resources (IBRs) is a term used to describe all of these generating technologies that are employed in electric power networks. Traditional synchronous generator (SG)-based voltage and frequency methodologies remain prevalent in the power sector, despite the expanding usage of IBRs. As a result, there’s an increasing demand for IBRs that can mimic the characteristics of SG, which is challenging to do with traditional grid-following inverters (GFLIs). Grid-forming inverters (GFMIs) are a relatively new thing that is gaining popularity in academic and industrial sectors as a viable solution. This chapter provides a complete review of GFMIs that includes modeling and recent advances in control technology. The energy sector is emphasizing the use of GFMIs to solve problems associated with weak grid scenarios, with recent reckon in Australia, the United Kingdom, and the United States serving as examples. Future directions are also considered in terms of voltage and frequency regulation, system strength development, and the regulatory regime. Researchers and power system engineers who are looking for solutions to the new challenges that have arisen as a result of high IBR penetration, with a focus on GFMIs, will find this chapter useful. The interactions between the IBRs and the high-power system are also discussed in this chapter. Inverters with GFMIs and GFLIs have a substantial difference. In a mixed system, GFM inverters dampen frequency swings, whereas GFL inverters can exacerbate frequency problems with increased penetration.