Grid-Forming Inverters: Shaping the Future of Power Distribution
Jul 5, 2023
12 min readAdd to Favourite
Jul 5, 2023
12 min readAdd to Favourite
As the penetration of inverter-based renewable energy (IBRE) resources continues to increase, the dynamics and control strategies of grids too have undergone significant advancements. Among these advancements, grid-forming inverters (GFI) have emerged as a groundbreaking technology with the potential to revolutionize the generation, distribution, and consumption of electricity. GFI technology finds widespread application in Battery Energy Storage System (BESS), wind power plants, solar PV plants, and hybrid plants, showcasing its versatility and effectiveness in optimizing energy systems and enhancing grid stability. While our understanding of GFI controls is still evolving, they hold tremendous promise for enhancing the performance of bulk power systems. With the rise of renewable energy sources and the growing complexity of power grids, traditional approaches to system operation face new challenges. GFIs are paving the way for the seamless integration of renewable energy, energy storage, and grid stability. In this article, we will delve into the transformative potential of GFIs and explore how they are reshaping the landscape of power systems, ushering in a new era of efficiency and adaptability.
The unintended separation of the grid due to equipment failures, severe weather conditions, or human errors in the presence of grid-following inverters faces limitations. These inverters are designed to follow the grid’s voltage and frequency, rendering them unable to continue supplying power and maintaining stability without a connection to the main grid. This highlights the limitations of grid-following inverters in such situations. To overcome these challenges and ensure smooth integration of renewable energy sources and battery energy storage into electric grids, alternative control methods are necessary. GFI controls offer functionalities similar to synchronous machines and prove beneficial in addressing these concerns. Exhibit 1 provides a comparison between grid-following and grid-forming modes of inverters, while Exhibit 2 highlights various categories of GFIs that incorporate diverse strategies.
GFIs offer the advantage of standalone operation, reducing complexity and dependence on external systems. They can effectively function in both high-inertia and low-inertia grids, adapting to changing system conditions. These inverters can serve as independent black-start resources, restoring the grid from outages without relying on a strong grid connection. This enhances overall system reliability. Transmission Operators establish interconnection requirements for GFIs, following NERC FAC-001 guidelines. Collaboration between Transmission Providers and Planning Coordinators ensures the accurate representation of field equipment through appropriate models during the interconnection process. Interconnection requirements for GFIs prioritize performance over a specific control strategy.
GFIs are still undergoing active development and commercialization by research organizations and manufacturers. While there is no standardized control method for GFIs in the industry yet, successful installations of GFI projects in the field and simulations have been carried out. Additionally, various projects are currently being developed to integrate GFI technology into inverter-based resources. Here are some existing and upcoming projects that have utilized GFI technology:
System operators in various countries are actively developing technical requirements for Grid-Forming Multi-Infeed capability which are mentioned below.
These efforts reflect the global interest in harnessing the potential of GFI technology to enhance grid stability and accommodate high levels of intermittent renewable energy sources.
Stakeholders involved play a crucial role in advancing the development, deployment, and integration of GFIs. Power system operators benefit from GFI as they enhance grid stability, voltage control, and frequency regulation. Energy regulators ensure compliance with standards and grid codes for safe and efficient operation. Inverter manufacturers contribute by designing and supplying efficient GFIs. Renewable energy developers rely on these inverters to seamlessly integrate renewable energy sources into the grid. Research institutions drive innovation and technological advancements, while industry associations facilitate collaboration and advocacy. Through their collective efforts, stakeholders support the effective implementation and widespread adoption of GFI, enabling a more resilient and sustainable energy system.
The deployment of advanced controls for IBRE faces a circular problem worldwide as illustrated in Exhibit-5. System operators and planners struggle to determine equipment capabilities and requirements for IBRE, resulting in operational constraints, curtailed output, and limited connectivity for IBREs. Manufacturers, lacking clear specifications and market incentives, are hesitant to invest in recent technologies. This cycle impedes the widespread deployment of advanced IBRE controls.
To break this cycle, collaboration between researchers, manufacturers, equipment owners, system operators, and policymakers is crucial in developing requirements, standards, technologies, and deployment mechanisms that reflect evolving grid reliability needs. Failure to do so may impede energy transition targets, increase transition costs, and hinder the achievement of a decarbonized future. Installing GFI technology resources can help avoid the need for larger grid-supporting devices or reinforcements in the future.
As the deployment of GFI continues to rise, their role on the grid is undergoing a transformation. Currently, grid-following IBREs, which rely on strong grid signals for operation, dominate the market. However, the increasing number of IBREs poses limitations on the effectiveness of GFI controls. To ensure grid stability, the adoption of advanced GFI controls becomes crucial.
GFIs offer voltage and frequency control, particularly in systems with full IBRE penetration. While GFI controls and their impact on bulk power system performance are still developing, the technology holds immense promise. Collaboration between system operators, manufacturers, and owners is essential to define system needs, comprehend equipment capabilities, and establish requirements for GFI technology adoption. Additionally, further research is necessary to assess stability and integrate various study processes. Embracing GFIs will pave the way for a future powered by clean and renewable energy sources.
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