Brazil's National Electric System Operator (ONS) and the Energy Research Company (EPE) released, on October 22, 2026, a new version of the technical note that defines the minimum technical conditions for connecting battery energy storage systems (BESS) to the grid. The document, identified as NT-ONS DPL 0111/2025 / EPE-DEE-NT-095/2025, will serve as a mandatory reference for bids in the Storage Capacity Reserve Auction (LRCAP), scheduled for 2026. The revision does not change the logic of the previous text: it brings specific clarifications and wording improvements, most notably the freedom to choose the format of dynamic simulation models.
What is new in the revision
The main substantive change concerns the mathematical models of electromechanical transients, which represent how the battery system behaves in response to grid disturbances such as short circuits, line losses or sudden frequency variations. With the new version, bidders may submit these models in the format of either the ORGANON or the ANATEM program, as they prefer. Both are tools used in stability studies of the Brazilian power system, and the option to choose between them tends to reduce rework for those who already have models ready on one of the platforms.
In addition, EPE and ONS made wording adjustments to several requirements. Although these are not changes in content, revisions of this kind usually remove ambiguities that created doubts of interpretation among developers, suppliers and designers, which matters in an auction where meeting the technical requirements is a condition for participation.
What the technical note requires from projects
The document covers the aspects needed for a battery plant to operate safely and in coordination with the transmission grid. Topics addressed include:
- Supervision: conditions for the operator to monitor the status of the facility in real time;
- Control: rules on how the system responds to commands and to grid conditions;
- Protection: requirements so that faults are isolated without compromising the power system;
- Telecommunications: communication infrastructure between the facility and the operation centers.
The note also sets parameters for the power converters, the equipment that bridges the direct current of the batteries and the alternating current of the grid. The converters must provide voltage and frequency control functions and operate in the grid forming strategy. In this mode, broadly speaking, the inverter does not merely follow the grid's voltage reference but helps form it, contributing to stability at points where the system is weaker or has a strong presence of renewable sources connected through power electronics.
Regulatory basis and auction context
The publication complies with the guidelines of MME Normative Ordinance No. 136/2026, which guides the work of ONS and EPE in defining the requirements for connection to transmission facilities. The LRCAP, in general terms, is the mechanism through which the government contracts power availability to ensure supply at times of peak demand, and the storage edition opens this space to batteries.
The revision comes amid a sequence of preparatory publications. A few days earlier, on October 19, EPE released the technical note with the methodology for defining the assumptions and parameters of the Reference Marginal Cost (CMR), which works as the price cap for the 2026 storage auctions. On October 16, the company published the registration and technical qualification instructions for hydraulic storage systems, signaling that the auction framework is being built on several fronts.
What this means for the Northeast
Connection requirements only make a difference where there is physical room on the grid to connect. According to ENLACE's survey, 27 eligible substations in Bahia, 24 in Ceará and 15 in Piauí are listed in the ONS connection margin technical note, which places these three states in a relevant position to receive bids in the Storage LRCAP.
In these areas, the grid forming requirement and voltage and frequency control carry additional weight, because much of the region already concentrates wind and solar generation connected through inverters. Projects that demonstrate robust dynamic performance in the models submitted to ONS tend to have smoother connection assessments.
Our take
In our assessment, the revision signals stability in the technical rules: requirements were not tightened; instead there were corrections and operational flexibility in model submission. For a market that is still debuting in battery auctions in Brazil, technical predictability is an asset, and we see this move as positive for those who had already been structuring projects based on the previous version.
The point of attention is the grid forming requirement. This is a functionality that not all converters offer with the same degree of maturity, and proving performance depends on well-validated models. We see a risk that bidders underestimate the modeling and integration effort among battery supplier, inverter manufacturer and designer, leaving to the final stretch adjustments that take time.
In the coming weeks, we will follow the consolidation of the other auction documents, especially the application of the CMR methodology published by EPE, and any new clarifications from ONS and EPE on the technical note. Any supplement to MME Normative Ordinance No. 136/2026 also deserves careful reading.
What changes in practice for the BESS chain
- Developers: should review their technical dossiers in light of the new version and decide now whether they will submit transient models in ORGANON or ANATEM, aligning this decision with suppliers.
- EPCs: need to incorporate supervision, protection and telecommunications requirements into the detailed design, avoiding generic solutions that do not address ONS requirements.
- Converter manufacturers: will have to prove voltage and frequency control and grid forming operation, with models compatible with at least one of the two accepted platforms.
- Suppliers and integrators: those able to deliver integrated packages, with technical documentation and validated models ready for connection studies, gain ground.
In short, the revision reduces friction in the qualification phase but maintains a high technical bar. Those who organize modeling and equipment selection early will reach the auction with less uncertainty.
Original source: EPE — EPE e ONS revisam Nota Técnica com os requisitos mínimos para o Leilão de Reserva de Capacidade (LRCAP) de Armazenamento de 2026
Paulo Melo