The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with larger amounts of wind and solar power, other sources will also be needed. Interesting possibilities include continuous control of wind and solar power, battery storage, electric vehicles, hydrogen production, and other demand resources with flexibility potential. The aim of this article is to describe and compare the different challenges and future possibilities in six systems concerning how to keep a continuous balance in the future with significantly larger amounts of variable renewable power production. A realistic understanding of how these systems plan to handle continuous balancing is central to effectively develop a carbon-dioxide-free electricity system of the future. The systems included in the overview are the Nordic synchronous area, the island of Ireland, the Iberian Peninsula, Texas (ERCOT), the central European system, and Great Britain.

The primary objective of electricity grids is to reliably meet the electricity demand at a minimum cost. This objective can be broken down into a set of needs that are met through services. These services are procured by mandating them either in grid codes or via market mechanisms. While grids in different countries/regions share common features in terms of needs and services, there are variations arising in physical, regulatory, and policy contexts. With the increased use of inverter-based resources (IBRs), such as wind and solar photovoltaic (PV) power and battery energy storage systems (BESSs), grids are undergoing changes that are altering the balance between needs and services. This balance is crucial in managing changes that will ensure that grids will continue to be able to meet demands. As increasingly more synchronous machines (SMs) are replaced by IBRs, the services inherently provided by the remaining SMs are dwindling, thus requiring the IBRs to contribute where they can.

The residential energy landscape is undergoing rapid transformation. In 2022, a record 700,000 U.S. homeowners installed solar, while nearly one in 10 cars purchased in the United States was an electrical vehicle (EV) ( Figure 1 ). In California, recent legislative reform incentivized the installation of home battery storage systems for load shifting, while Senate bill SB 233 requires that all EVs are capable of bidirectional charging. The bill was also designed to reverse a troubling trend: In recent years, Californians have increasingly responded to power outages and rolling blackouts by purchasing diesel-propelled backup generators. In contrast, some EV batteries now have the ability to power a home for up to three days and so are considered a “green” alternative to diesel generators. Federal Energy Regulatory Commission Order No. 2222 has also increased the competitiveness of distributed energy resources (DERs) by enabling them to participate in regional wholesale markets through aggregations. Indeed, commercial equipment combining bidirectional EV charging and solar energy conversion that fully integrates with home battery storage can be leveraged as DERs. This can significantly improve grid reliability, while deferring costly infrastructure upgrades and enhancing decentralized resiliency by powering homes during blackouts.

The integration of renewable energy resources and power electronic interfaced devices, such as inverter-based resources (IBRs), into the grid has introduced unique challenges in ensuring power system stability and reliability. Electromagnetic Transient (EMT) modeling is becoming increasingly important for connection studies, enabling the detailed analysis of IBR dynamic behavior. This paper reviews the evolution and current applications of EMT modeling in connection studies across North America, Europe, and Australia. It highlights the increasing use of EMT simulations for grid impact assessments, compliance verification, and mitigation of stability concerns, such as sub-synchronous interactions and voltage stability in weak grid conditions. Case studies and industry surveys reveal best practices for model development, validation, and integration in multivendor, multiparty projects. Additionally, the paper highlights the importance of the collection of high-fidelity models during the interconnection process to address future planning needs. By promoting a collaborative approach among stakeholders—Original Equipment Manufacturers, transmission operators, and developers—this article provides critical insights into advancing the adoption of EMT modeling to support energy transition.

This article introduces general readers to the use of Electromagnetic Transient Modelling (EMT) simulations in a modern power system context. It covers the salient differences between traditional phasor domain transient and EMT tools, extending from fundamental representation differences in the tools to consequential deviations in transient stability simulation results and conclusions. It considers the benefits and drawbacks of adoption of EMT for power system analysis, with additional consideration of non-technical challenges which may arise. Finally, it provides a brief introduction to screening methods which may be used to decide where the use of detailed EMT studies is required.