Why is Grid Forming important?

Great Britain’s electricity system is increasingly relying on clean energy sources such as wind and solar to help reach Net Zero. NESO’s role is to use these technologies to balance electricity supply and demand while maintaining a stable and secure system.   

As the system changes, it is important to adopt technologies that support its strength and resilience. These include both traditional synchronous technologies, like gas and nuclear power stations, technologies that can produce the same results as power stations, without creating electricity, such as synchronous compensators, and inverter based technologies such as Grid Forming batteries. Together, these are known as Grid Forming technologies, and they help maintain system stability. 

Most renewable generation such as batteries and solar plant produce direct current (DC), but homes and businesses use alternating current (AC). An inverter is a power electronics device which converts DC to AC. There are two main types of inverters: 

• Grid Following inverters, which rely on the existing system voltage and frequency to operate 
• Grid Forming inverters, which can create their own voltage and frequency 

Most inverters today are Grid Following. They depend on the system to operate and provide limited support during disturbances, such as faults on the network. Grid Forming technologies however, can operate more independently. By creating their own voltage and frequency, they can support system stability and provide inertia, similar to traditional power stations. As more Grid Following technologies connect to the system, a minimum level of Grid Forming capability will be needed to ensure the system remains stable. 

You can learn more about Grid Forming technologies on the NESO website: 

What is Grid Forming?

What Has NESO Been Doing? 

Since 2019, NESO has run competitive tenders, formerly known as Stability Pathfinders, to secure stability services from Grid Forming technologies. Early Stability Pathfinder tenders helped bring forward new providers including Grid Forming Batteries in Scotland: 

These tenders have now evolved into enduring Stability Markets, where providers compete to deliver services that meet technical requirements at the lowest cost. 

Grid Forming Requirements 

The rulebook for connecting to and operating on the GB Power System, is called the Grid Code. It sets the minimum requirements that anyone connecting a generator or demand to the system needs to meet to be able to connect, this includes the minimum rules for Grid Forming. 

To take part in NESO’s Stability Markets (where companies can be paid for helping deliver stability services), they might need to meet higher performance standards than the basic Grid Code rules. 

Some key things Grid Forming equipment are required to do in the Grid Code include: 

1. Active RoCoF Response Power (inertial response) 

   This is the plant’s active power response proportional to the rate of change of frequency (RoCoF) when system frequency changes.  

2.  Active Phase Jump Power 

   This is the plant’s active power response to phase angle changes, and its ability to remain stable during sudden changes in system angle. 

3. Fast Fault Current Injection 

   This is the plant’s rapid injection of current in response to a sudden voltage drop caused by a system fault and supports voltage and system strength. 

To be considered for a contract in NESO’s Stability Markets, or for the Electricity Restoration Service, providers must demonstrate their technology meets NESO’s requirements before being contracted. 

Grid Forming Batteries  

Grid Forming batteries are an emerging technology, and both NESO and industry are continuing to develop understanding of how best to deploy and operate them. 

As these technologies evolve, NESO continues to review the Grid Code, including considering whether to require Grid Forming capability for new plant. As the electricity system becomes more reliant on inverter-based generation, this can help ensure sufficient Grid Forming capability is available to maintain system stability and deliver benefits to consumers. 

Both synchronous and inverter-based technologies will be needed to support a stable and resilient system. NESO will continue to procure stability services through its markets, ensuring competition between technologies and refining procurement approaches and participation requirements where needed. 

NESO has also engaged with industry through a recent Grid Forming webinar, which provided an overview of requirements in Great Britain, including relevant Grid Code provisions and commercial compliance processes. 

A recording of the webinar is available on the NESO website: 

Grid Forming Webinar