The Brazilian Association of Energy Storage Solutions (ABSAE) published on October 1, 2026 a response to criticism from the thermal power sector about the role of batteries in the security of the electricity system. The debate gained momentum after the Ministry of Mines and Energy (MME) included storage systems in the Capacity Reserve Auctions (LRCAP), within a schedule that runs through 2029. According to the association, the rules already defined for the December battery auctions directly address the technical concerns raised by critics.
What the critics say and what the response is
The argument put forward by thermal plant representatives is that battery energy storage systems (BESS) would be unable to guarantee voltage and frequency stability on the grid, or to supply short-circuit current in sufficient volume. These are attributes that have historically come from large synchronous machines, such as turbines at thermal and hydroelectric plants, whose rotating mass helps dampen disturbances.
ABSAE disputes this view by pointing to the regulatory design of the auction itself. The association notes that MME Normative Ordinance No. 136/2026, which governs the battery auctions scheduled for December, does not accept just any equipment: it requires the use of grid forming inverters, in accordance with the parameters of a technical note prepared jointly by the National Electric System Operator (ONS) and the Energy Research Company (EPE).
The technical requirements for inverters
To understand the discussion, it is worth explaining the basic difference between the two types of inverter. The conventional model, called grid following, tracks the voltage and frequency already imposed by the grid and injects energy based on that reference. Grid forming, on the other hand, creates its own voltage and frequency reference, behaving much like a synchronous generator. This allows the battery to help support the grid rather than merely follow it.
The requirements of the ONS/EPE technical note, as highlighted by ABSAE, include:
- Response to phase jumps within 16 milliseconds;
- Reaction to frequency variations within 200 milliseconds;
- Synthetic inertia, which electronically emulates the stabilizing effect of rotating masses;
- Black start capability, that is, the ability to help restart parts of the system after a blackout, as an option.
In the association's argument, this set of requirements shows that the auction was designed to contract batteries that provide stability services, not just energy shifting throughout the day.
The locational bonus and the MISCR indicator
The second point highlighted by ABSAE is the locational bonus mechanism. The auction uses the MISCR indicator to guide project siting, favoring points on the grid considered weak. In general terms, indicators in this family measure the ratio between the strength of the grid at a given point, expressed by short-circuit power, and the amount of inverter-based generation connected there. The lower the value, the more fragile the point tends to be in the face of disturbances.
The logic is to place equipment capable of forming the grid precisely in these locations, where its contribution to stability tends to be greatest. The association cites the experiences of the United Kingdom and Australia as international references for the use of batteries in this role.
What this means in the Northeast
Because the auction rewards connection at weak grid points, the choice of substation becomes as important as the price of the equipment. In ENLACE's survey of Northeast substations eligible for LRCAP 2026, cross-referenced with the ONS technical note on connection margin, Bahia has 14 substations with a margin of 500 MW or more, Ceará has 10 and Piauí has 6. These figures indicate where there is physical room to connect large-scale projects.
There is, however, an important nuance: connection margin and grid weakness are different things. A point with headroom to receive power will not necessarily have the MISCR that secures the bonus. For this reason, site screening in the region needs to combine both layers of analysis, rather than looking only at available capacity.
Our take
In our assessment, ABSAE's response signals that the debate over batteries in Brazil is no longer about whether they should participate in capacity auctions but about how they should participate. By tying procurement to grid forming inverters and siting criteria, the ordinance turns BESS into a grid service asset, which we see as a maturing of the market and a way of responding to technical objections through regulation.
There are still points to watch. The millisecond performance requirement depends on verification, and the market will need to understand how the requirements of the ONS/EPE technical note will be checked in practice, both at qualification and during operation. We also see a risk that the locational bonus will concentrate competition in a few points, increasing competition for access precisely where the grid is most sensitive. And the criticism from the thermal sector, even if rebutted, shows that the coexistence of sources in upcoming auctions will remain under discussion.
In the coming weeks, we will follow the preparation of the December battery auctions governed by MME Normative Ordinance No. 136/2026, any clarifications on the application of MISCR, and the continuation of the MME schedule for the LRCAP through 2029, which will determine how often new opportunities are likely to arise.
What changes in practice for BESS developers
- Developers need to review site selection, cross-referencing connection margin with the MISCR indicator to pursue the bonus without losing access feasibility.
- EPCs must incorporate the required dynamic performance studies into the project, including response to phase jumps, frequency control and, where applicable, black start.
- Inverter manufacturers and integrators will have to offer grid forming solutions compliant with the parameters of the ONS/EPE technical note, with documentation and testing to support that compliance.
- BESS suppliers in general should prepare for bids evaluated not only on cost and storage capacity, but on their actual contribution to grid stability.
Original source: ABSAE — Um portfólio de potência mais seguro e eficiente passa pelos Sistemas de Armazenamento de Energia em Baterias
Paulo Melo