Winding down: NGESO proposes virtual inertia specifications

By this time next year, intermittent generation may be able to provide virtual synchronous services to the industry under a new Grid Code modification proposal.

Raised by National Grid Electricity System Operator (NGESO), GC0137 Minimum Specification Required for Provision of Virtual Synchronous Machine (VSM) Capability seeks to create requirements for Virtual Synchronous Machines (VSMs). These allow generators which do not operate at the same frequency as the rest of grid to function as if they were, reducing the effect they have on system inertia.

System inertia is essentially how rapidly the system frequency responds to change. It has steadily reduced over recent years as more and more intermittent generation comes online and traditional synchronous generation moves off the system. Traditional generators like coal plants, combined cycle gas turbines and hydropower stations have their turbines spin at 3,000rpm so they generate electricity at 50Hz, matching the frequency of the system. If they suffer a fault, inertia means they do not stop spinning immediately so frequency drops more slowly. However, most renewables are asynchronous as they are connected via an inverter, so do not work this way, which[VT1]  gives NGESO[VT2]  less time to respond to system issues and increases the cost of managing the system.

VSM technology provides a solution, in which case the asynchronous generator uses its power electronics to mimic a synchronous one. This would mean a fault will not cause frequency to drop so sharply, giving NGESO more time to take other actions. GC0137 envisions specifications for what VSM capability should look like so that it can operate in a market-based service. NGESO has not yet published the appendix which sets out the specifics of this, but indicated an updated draft could be circulated in January. Commercial details are to be discussed and agreed at a later date.

The modification will be presented to the Grid Code Panel on 19 December and NGESO said it intended implementation would be in Q320. However, timescales will depend on how quickly a VSM specification can be agreed. NGESO expects that enabling VSM should lead to improvements in its own ability to balance the system and revenue opportunities for generators.

We provide regular coverage of regulatory issues relating to flexibility in our Flexibility Matters service, helping you understand what changes mean for you and your assets. For more information, contact Steven Britton at or on 01603 542126.

Related thinking

Energy storage and flexibility

Waiting to connect: the problems and solutions for network connection queues (Part 2)

Network connection queues continue to be a notable topic of interest as many generators face significant delays to project development – an issue that is directly conflicting with net zero ambitions and recent focuses on strengthening domestic energy supplies. In Part 1 of our two-part series on connection queues we...

Energy storage and flexibility

Waiting to connect: the problems and solutions for network connection queues

The number of grid applications has risen significantly in recent years, resulting in increased pressure on the electricity networks to facilitate new connections. In its Energy Security Strategy, the UK government set out ambitions for 95% of electricity to be sourced from low carbon generation by 2030, and for the...

Power and gas networks

Gas DSR reforms ahead of winter 2022-23

National Grid has recently carried out a review of the Gas Demand Side Response (DSR) voluntary curtailment mechanism through July and August. The Gas DSR allows shippers to offer a consumption curtailment service to National Grid Gas (NGG) during periods of acute gas supply constraint called a Gas Deficit Emergency...

Energy storage and flexibility

Dialing up the unknowns on network charging

In a world of open governance code modifications, change is a constant. You only have to look at the number of code modifications ongoing at any one time – National Grid lists 36 modifications in development relating to transmission network charging alone – for evidence of that. But in recent...

Commercial and market outlook

Capacity, reform, and unlawful strategies: 5 things that happened yesterday

Capacity, reform, and unlawful strategies: yesterday was a busy day for energy geekery. The developments encapsulate the shorter and longer term challenges and uncertainties present in the energy market presently: Read the full article here

Business supply and services

Re-balancing the balancing costs –BSUoS charges to be levied solely on suppliers from April 2023

Balancing the electricity system costs money. National Grid in its role as Electricity System Operator (ESO) takes actions in every half hour to achieve the remarkable feat of keeping supply and demand finely balanced on our national electricity system – maintaining a system which runs between 49.8 and 50.2Hz with...

Energy storage and flexibility

Dynamic Regulation launches

National Grid ESO (NGESO) launched the Dynamic Regulation (DR) service on 8 April, with the first auction held at 14:30 on the EPEX auction platform. DR is the second new product that the ESO has introduced to manage frequency on the system, as the system operator introduces a suite of...

Business supply and services

Wholesale energy prices see new record highs as 2021 comes to a close

In what continues to be a particularly tumultuous period for the wholesale energy market in the lead up to Christmas, prices have continued their crusade of setting record highs in a final send-off to 2021. On Wednesday 22 December, day-ahead gas prices reached a new all-time record high (on our...