India’s ambitious climate and energy transition agenda, targeting 500 GW of non-fossil fuel generation capacity by 2030 and net-zero emissions by 2070, is driving rapid expansion of renewable energy capacity, particularly wind and solar power. However, the growing integration of inverter-based renewable resources introduces new operational challenges related to system strength, voltage stability and dynamic response during grid disturbances.

To address these emerging challenges, Grid Controller of India Limited (GRID-INDIA), the country’s national power system operator, released a discussion paper titled “Grid-forming technology and possible applications in the Indian Power System”. The paper examines whether this emerging technology can enhance system reliability and stability in a high-renewable power system. The study explores the performance of grid-forming (GFM) inverters compared with the currently dominant grid-following (GFL) inverters through literature reviews, international deployment experiences, and detailed simulation studies on standard test systems and an all-India power system model.

GFL vs GFM inverter technology

The GFM technology offers significant advantages over conventional GFM controls. One of the defining capabilities of GFM inverters is their ability to operate in islanded modes. Even in the absence of synchronous generators, they can independently establish and regulate voltage and frequency, enabling the formation of stable and self-sustained microgrids. This capability also supports black-start operation, allowing GFM inverters to energise a de-energised network after a widespread outage. In addition, it enables seamless transitions between grid-connected and islanded operation. During grid disturbances, a local network can disconnect from the main grid and continue operating autonomously while maintaining voltage and frequency stability. Once normal grid conditions are restored, the network can be reconnected without adversely affecting system stability.

Additionally, GFM inverters contribute to frequency stability in low-inertia power systems. As a result, they are capable of providing essential grid services, including primary and secondary frequency control, reactive power support and damping of power system oscillations. However, many of these functions depend on the availability of a power reserve, since the inverter must be able to rapidly adjust its output to stabilise the system. For this reason, GFM inverters are commonly deployed with battery energy storage systems (BESSs).

Simulation-based study results

The discussion paper assesses the performance of GFM inverters through simulation studies on benchmark test systems and a detailed all-India power system model, with a particular focus on renewable energy complexes in the Indian state of Rajasthan. By comparing GFM and GFL technologies under weak-grid conditions, high renewable penetration, and system disturbances, the study evaluates the potential of GFM controls to enhance stability, strengthen fault response, and support reliable operation of an increasingly inverter-dominated grid. The study identified several benefits associated with GFM deployment:

  • Better performance in weak grids: While GFL inverters can become unstable when grid strength is low, GFM inverters remain stable and support reliable grid operation.
  • Better voltage stability: During grid disturbances, GFM inverters improve voltage performance through effective reactive power response and inherent damping. This helps reduce the severity of voltage dips during faults and limit post-fault voltage spikes.
  • Faster recovery after disturbances: In scenarios involving multiple line outages or delayed recovery from GFL-based plants, GFM technology accelerates active power recovery and reduces the risk of transmission overvoltage.
  • Stronger frequency response: By emulating inertia, GFM inverters respond rapidly to frequency deviations. This rapid response lowers the rate of change of frequency (RoCoF), particularly near disturbance locations, and helps prevent cascading outages.
  • Impact of placement strategy: The effectiveness of GFM deployment depends on where the inverters are installed. Distributing GFM capability, rather than concentrating it at a single node, provides wider improvements in voltage performance and RoCoF across the system.
  • Scalable benefits with higher penetration: The study indicates a positive relationship between GFM penetration and overall system performance. Higher levels of deployment are associated with improved voltage stability, faster fault recovery and reduced RoCoF.

Importantly, the results show that the benefits of GFM technology are not uniform across the system. They are most pronounced in weak grid areas and regions with high IBR penetration, suggesting that targeted deployment is likely to deliver greater value than a uniform, system-wide roll-out.

The way forward

GFM technology is already being deployed in several countries, including Australia, Great Britain, the US and the Middle East. This highlights the need for well-defined functional specifications and rigorous performance validation to ensure consistent implementation across different power systems. Recognising this, many system operators, research institutions and regulatory bodies have published technical requirements and guidelines for GFM capabilities. Continued research in this area is expected to further drive progress toward international standardisation and enable the smoother integration of IBRs. These international developments also provide useful reference points for the evolution of India’s grid codes and technical standards.

GRID-INDIA has proposed a set of measures to support the adoption of GFM technology in the Indian power system. Given the growing role of BESS, it is recommended that new BESS installations above 50 MW, particularly in remote or weak-grid areas, incorporate GFM capability. A phased roll-out is suggested, beginning with large pilot projects using BESS-backed GFM inverters. These pilots would provide operational experience and help stakeholders make informed decisions for wider deployment. In parallel, aligning Indian standards with international testing and performance frameworks would help ease the transition.

Effective implementation will also require close coordination between technology providers, renewable and storage developers, system operators and regulators. This is essential to ensure that different technologies interact safely and reliably within the grid. Looking ahead, further research may also focus on the conversion of existing GFL inverters to GFM operation, standardisation of equipment and development of technical specifications for black-start applications. The paper also emphasises the need to integrate fault recording and sequence-of-events recording within GFM inverters to allow detailed assessment of control performance during disturbances. In addition, it calls for stronger compliance verification, improved model transparency and targeted stability studies in weak-grid areas.

At present, the primary focus remains on inverter-level applications in solar, wind and BESS. However, future studies may also explore the application of GFM concepts at the transmission level, including their use in static synchronous compensators and high-voltage direct current converter stations. Overall, the discussion paper outlines a structured roadmap for the adoption of GFM inverter technology in India, marking an important step toward a more stable and resilient power system increasingly characterised by high renewable energy penetration.