Standards Development

Scope

This TS establishes a framework recommending technical minimum functional capability and performance requirements as well as model-based test procedures and test criteria for grid- forming equipment used in converter-based resource (CBR) plants. It applies to CBRs of any scale that are connected to and operate in parallel with electric power systems. Grid - forming (GFM) equipment that does not interface with the power system via power electronics is not in the scope.

This TS specifies capabilities and performance requirements; actual utilization of these capabilities in any given application is outside of the scope of this standard.

Purpose

The global energy sector is undergoing a fundamental transformation driven by the rapid expansion of renewable energy technologies. By the end of 2024, global renewable generation capacity reached 4,448 gigawatts (GW), reflecting a significant year -over-year increase. This growth is primarily led by solar photovoltaics and wind power, both of which are predominantly converter-based resources (CBRs). Renewables accounted for 85.5% of global capacity additions, signalling a marked decline in the role of conve ntional synchronous generation.

According to the International Energy Agency (IEA), by 2028, renewable sources are projected to account for over 42% of global electricity generation, with wind and solar PV alone contributing 25%. This structural shift toward variable and non -synchronous generation is redefining grid operation paradigms.

The increasing penetration of CBRs, coupled with the retirement of synchronous generators (SGs), introduces new challenges for power system stability and control. Conventional grid services such as system strength, frequency regulation, inertial response, voltage support, and fault current provision—historically delivered by SGs—are no longer intrinsically provided by CBRs.

In this context, grid-forming (GFM) inverters have emerged as a potential enabling technology. Unlike grid-following inverters, GFM inverters are capable of independently establishing voltage and frequency reference points, contributing virtual inertia, an d operating in weak-grid conditions. They emulate in part the dynamic behaviour of SGs, making them essential for maintaining power system stability as renewable penetration increases.

Despite growing interest and initial deployment efforts, the lack of an internationally recognized standard for GFM inverters presents significant barriers to wider adoption. The current absence of harmonized definitions, performance criteria, and test pro cedures leads to:

 Inconsistent performance expectations across manufacturers and jurisdictions,

 Interoperability issues in mixed-vendor or hybrid systems,

 Integration and coordination difficulties for system operators,

 Regulatory uncertainty for developers and grid planners.

Given these issues, the development of a TS for grid -forming inverters is a critical priority. This should be evolved into an international standard in a further step.

This TS specifies—for example but not limited to—definitions, capability tiers and associated functions (like active and reactive power sharing, grid strength adaptability, inertial response, damping control, operation under system unbalance, resistance to voltage phase angle jumps, voltage harmonics regulation, overload capacity, and blackstart capability) and frequency domain characteristics (like passivity etc.) for equipment of CBRs that operate in GFM mode.

Non-GFM specifications are not included in this TS. The TS is intended to supplement existing national and international capability and performance standards, requirements or related specifications that address the general performance, safety, and grid con formity of converter-based technologies, particularly those operating in grid -following (non-grid- forming) modes. It does not duplicate requirements already established for such existing modes but instead focuses exclusively on the additional functional at tributes and behaviours associated with grid-forming capabilities. It is intended to apply in conjunction with those standards and not supersede or replace them.

The TS is intended for use by inverter manufacturers, grid operators, system integrators, and regulatory bodies to ensure consistent implementation, interoperability, and safe integration of grid-forming inverters into electric power systems with high shares of renewable energy.

Establishing such a TS would align with ongoing global efforts to modernize grid infrastructure, support decarbonization goals, and enable secure operation of high - renewables power systems. It would also enhance collaboration between manufacturers, utilities, system operators, and regulators by providing a common technical foundation