The Grid Controller of India (GRID India) has proposed a significant regulatory shift to mandate grid-forming (GFM) capabilities for all new battery energy storage systems (BESS) with a capacity exceeding 50 MW at the time of granting connectivity. This recommendation, highlighted in recent industry reports and a GRID India discussion paper, is designed to bolster grid stability in weak-grid or remote areas. The proposal serves as a critical technical roadmap for managing India’s transition to a power system dominated by high-penetration inverter-based resources (IBR).
The Grid-Forming Mandate and Technical Requirements
In the discussion paper titled “Grid Forming Technology and Possible Applications in Indian Power System,” GRID India recommended to the Central Transmission Utility (CTUIL) that the 50 MW threshold should trigger mandatory GFM integration. A key technical nuance in the proposal specifies that the solar generation source paired with or used for charging the BESS must possess a GFM capacity equivalent to 25% of its total capacity. This requirement provides an additional layer of system anchoring beyond the BESS unit’s own capabilities.
GRID India suggests that these safeguards are essential for maintaining reliability in pockets of the grid where system strength is low and the risk of instability is high.
Technical Rationale: Moving Beyond Grid-Following (GFL) Inverters
The transition toward GFM technology is necessitated by the inherent limitations of conventional Grid-Following (GFL) inverters. While GFL systems are mature, they are dependent on a “stiff” grid signal for synchronization. Their performance degrades in environments with a low Short Circuit Ratio (SCR)—a measure of the system’s strength relative to the connected generation. GFM inverters, by contrast, act as voltage sources that can establish their own references.
The following table compares the performance profiles of these two technologies based on GRID India’s technical assessment:
| Grid-Following (GFL) Limitations | Grid-Forming (GFM) Capabilities |
| Operational Mode: Functions primarily as a current source, injecting power setpoints into an existing grid signal. | Operational Mode: Functions as a controllable voltage source, autonomously establishing voltage and frequency references. |
| Synchronization: Highly dependent on Phase-Locked Loop (PLL) signals; prone to loss of synchronism in weak grids. | Synchronization: Inherent synchronization capability without PLL dependence; enables “virtual inertia” and damping. |
| System Strength: Performance deteriorates in low Short Circuit Ratio (SCR) environments, leading to oscillations. | System Strength: Designed for robustness in weak-grid and high-IBR (>50%) penetration environments. |
| Grid Contribution: Focuses on self-protection; often shuts down during instability, which can exacerbate grid events. | Grid Contribution: Provides active grid support, including black-start capability and autonomous islanded operation. |
GRID India’s simulations, conducted on the all-India model and Rajasthan’s renewable energy complexes, identified several measurable benefits of GFM adoption:
- Shallower fault-induced voltage dips: Minimizing the depth of drops during grid disturbances.
- Overshoot suppression: Providing rapid reactive power (Q) support to mitigate post-fault voltage spikes.
- Reduction in Rate of Change of Frequency (RoCoF): Delivering instantaneous inertia-like response to stabilize frequency.
- Faster system recovery: Reducing settling times to prevent cascading trips in large renewable energy clusters.
Grid Stability Risks and VRE Growth
The urgency for advanced inverter control is underscored by India’s goal to reach 500 GW of non-fossil capacity by 2030. This growth has already led to instantaneous variable renewable energy (VRE) penetration exceeding 100% in states like Karnataka. However, this transition has introduced operational volatility.
Between January 2022 and July 2025, the Indian grid recorded 68 VRE loss events that each exceeded 1 GW of generation. These incidents were primarily concentrated in the high-penetration regions of Rajasthan, Gujarat, and Karnataka. Technical analysis of these events identified the following triggers:
- Shortfalls in High-Voltage/Low-Voltage Ride-Through (HVRT/LVRT) compliance.
- Phase-Locked Loop (PLL) instability under weak grid conditions.
- Scalar current logic flaws and conservative Over-Voltage (OV) settings.
- Anti-islanding mis-trips and excessive RoCoF.
Regulatory Context and Future Implementation
The GRID India proposal aligns with the upcoming “Central Electricity Authority (Technical Standards for Construction of Electrical Plants and Electric Lines) Regulation, 2026.” According to the notification, these standards are set to commence on April 1, 2027. Under Chapter-VI, Part-C of these regulations, BESS installations with an installed capacity of 50 MW and above are required to possess specific advanced capabilities.
Mandatory requirements for these large-scale systems include:
- Grid-forming inverter capability.
- Automatic Generation Control (AGC).
- Black-start capability.
The implementation roadmap suggests a phased approach, beginning with large-scale BESS-GFM pilot projects to validate protection models and operational stability. Furthermore, Indian standards are being aligned with international frameworks, specifically those developed by the Universal Interoperability for Grid-Forming Inverters (UNIFI) consortium.
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