The Grid Controller of India (GRID India) has suggested to the Central Transmission Utility (CTUIL) that all new battery energy storage systems (BESS) above 50 MW be mandated to have grid-forming capability at the time of granting connectivity.

The measure, to be in place until the Central Electricity Authority’s (CEA) Construction Standards for Renewable and BESS are notified, will ensure adequate system strength for reliable system operation while granting non-solar hour connectivity at existing pooling stations.

GRID India further suggested that dedicated solar generation accompanying BESS for charging purposes should also have grid-forming capability for at least 25% of its capacity.

It said other measures to ensure adequate system strength, such as the installation of synchronous condensers, must be explored by CTUIL.

These suggestions come in the context of the Short Circuit Ratio (SCR) at several renewable energy pooling stations being below the stipulated value of ‘5’ in CEA Connectivity Standards.

In January, a GRID India discussion paper proposed that BESS installations of 50 MW or more should have grid-forming capability, especially when located in weak grids or remote areas. It had noted that grid-forming inverter technology (GFM) is becoming commercially viable and field-proven for transmission-connected applications, as evident from international deployments.

Last September, the government tasked the CEA with conducting a pilot project on grid-forming inverters in the wake of a power blackout in the Iberian Peninsula that disrupted power supply for hours on April 28, 2025. The CEA had also initiated an exercise to ascertain GFM’s domestic manufacturing capacity and asked manufacturers to share the data.

Low system strength is a key contributing factor to oscillations and other stability issues being frequently observed in renewable energy complexes in India’s power system, such as Rajasthan in the Northern Region, and Khavda and Pachora in the Western Region.

Experiments carried out during the outage of 400 kV Bikaner (PG) – Bikaner-II D/C and 400 kV Pachora-Bhopal Ckt-1 have established that low SCR/system strength significantly increases the susceptibility of renewable energy complexes to oscillatory instability.

The increase in inverter-based capacity at these pooling stations, with the addition of BESS along with dedicated renewable energy generating stations for charging, is expected to significantly reduce the SCR and lead to stability issues.