As conventional power plants with large rotating turbines are replaced by inverter-based Distributed Energy Resources (DERs) like solar PV and batteries, the power system is losing its natural physical inertia. This inertia is critical for stabilising the grid’s frequency immediately following a fault or sudden change in load. Low Voltage (LV) Inertia, also known as Synthetic or Virtual Inertia, is the solution to this challenge. It is a capability provided by advanced power electronics (specifically grid-forming inverters) that enables DERs to actively mimic the stabilising behaviour of traditional generators. This decentralises grid stability, moving it from large transmission-connected plants to the medium and low-voltage grids edge where the new generation is located.
Highlights
The need for virtual inertia is rapidly accelerating as renewable penetration targets increase. System operators globally are beginning to recognise inertia as a critical ancillary service that must be actively managed. Regulatory bodies are starting to update grid connection codes to mandate grid-support functions, including inertia, from new DER connections. This represents a fundamental shift from a passive distribution network to one where a significant number of small assets actively contribute to the stability of the entire power system.
Opportunities for DSOs
- Increased DER Hosting Capacity: By providing local stability, LV inertia allows DSOs to safely connect significantly more solar PV, batteries, and EV chargers onto their networks without violating technical limits or causing instability, unlocking new revenue streams.
- Enhanced Grid Resilience: DERs with grid-forming capabilities can create stable, self-sufficient microgrids. This enables intentional islanding to keep power on for critical facilities or communities during a wider grid outage, dramatically improving reliability.
- Improved Power Quality: Grid-forming inverters provide a strong, stable voltage waveform locally. This helps to mitigate voltage sags, swells, and other disturbances on the LV network, improving the quality of supply for all customers.
- New Ancillary Service Markets: DSOs could play a role as market facilitators or aggregators, procuring inertia as a paid service from customers with capable DERs. This creates a new value stream for customers and a new tool for the DSO to manage their network.
Challenges for DSOs
- Technology Cost and Maturity: Grid-forming inverters are more complex and currently more expensive than the standard grid-following inverters that dominate the market. A clear business case is needed to justify the incremental cost.
- Control and Coordination Complexity: Managing the stability contributions of thousands or millions of distributed devices is a major technical challenge. It requires advanced Distribution Energy Resource Management Systems (DERMS) to ensure they work in harmony and not against each other.
- Lack of Standards and Interoperability: There is an urgent need for industry-wide standards to ensure that grid-forming devices from different manufacturers are interoperable and their behaviour is predictable.
- Protection System Redesign: Grid-forming inverters have different fault current characteristics than traditional generators. Existing LV network protection schemes (e.g., fuses and circuit breakers) may not operate correctly and will likely require re-evaluation and redesign. Anti-islanding protections may not be effective with generators equipped with Grid-forming inverters. New protections will have to be designed and installed.
E.DSO Considerations
- Advocate for Updated Grid Codes: DSOs must actively participate in regulatory discussions to update national and European grid connection codes, ensuring that new DERs are required to have grid-forming capabilities.
- Develop New Connection Agreements: Connection agreements should be revised to specify the required grid support functions, including inertia provision, from new and existing DERs.
- Invest in Digitalisation and Skills: DSOs must invest in the DERMS platforms, communications infrastructure, and engineering skills necessary to monitor, control, and validate the performance of these distributed stability resources.
- Launch Pilot Projects: It is crucial for DSOs to engage in pilot projects to gain hands-on experience, test control strategies, and understand the real-world costs and benefits of deploying virtual inertia solutions on their networks.
Potential Use Cases
- High-Penetration Solar Feeders: Deploying grid-forming community batteries on LV circuits with high solar PV saturation to absorb excess generation while ensuring the local grid remains stable and within voltage limits.
- Weak or Rural Grids: Using a grid-forming battery system to “stiffen” the grid at the end of long, rural feeders, improving power quality and enabling the connection of new renewable generation or EV charging.
- Resilient Critical Infrastructure: Creating stable microgrids for hospitals, airports, or data centres that can seamlessly disconnect from the main grid during an outage and continue to operate reliably.
- Large EV Charging Hubs: Requiring new, large-scale EV charging depots to include integrated grid-forming battery storage, making them self-sufficient in terms of stability and capable of providing support services back to the grid.
Ongoing Projects & Initiatives
- UK Power Networks (UK): The “Constellation” project is a trial to manage DERs as a coordinated group to provide a range of services, including stability, by creating a virtual synchronous machine.
- A-P-P-L-A-U-S-E Project (Germany): A research initiative focused on developing control strategies for large populations of grid-forming inverters to ensure stable operation of future power systems.
- National Grid ESO (UK): The “Pathfinder” programme, while at the transmission level, is a world-leading initiative procuring inertia and other stability services from non-traditional sources like batteries, setting the market precedent for DSOs.
- SUREVIVE Project (Germany): A lighthouse initiative testing grid-forming inverters and intelligent battery storage under real grid conditions to validate their role in providing instantaneous reserve and stabilizing distribution networks. The project explores innovative control concepts and aims to enable black start capability, frequency support, and energy balancing in future renewable-based grid
- National Grid ESO – Stability Pathfinder Phase 2 (UK): A strategic response to the growing low inertia challenge in Scotland, driven by the retirement of synchronous generators and the rise of renewables. The programme awarded £323 million in contracts to innovative technologies that can deliver inertia and short-circuit current without relying on traditional spinning machines. This initiative is key to maintaining grid stability in low-inertia conditions and sets a benchmark for future DSO-level services.
- Enedis (France): Enedis has financed and supervised several PhD theses and research projects on the operation of microgrids, particularly on the control of inverters (Grid Forming / Grid Following). The objective is to design innovative solutions to reduce the cost of implementing micro-grids (small systems without rotating machines and, if possible, without batteries, or with only a as small as possible battery). Furthermore, Enedis finances and contributes to the monitoring, together with the French TSO (RTE), of a thesis on the global system recovery after a widespread incident using renewable energy production means connected to the MV network.
Last update: 8 December 2025