Smart controllers help Brazilian PV projects bypass reverse power flow constraints

Smart controllers help Brazilian PV projects bypass reverse power flow constraints Restrictions imposed by Brazilian utilities due to reverse power flow have prompted solar installers and PV system owners to adopt new strategies to keep distributed generation projects viable. When electricity generation exceeds on-site consumption and multiple PV systems are connected to the same feeder, utilities may be unable to transfer all surplus electricity to other parts of the grid. This can lead to voltage fluctuations, overloaded equipment, and reduced grid stability. The severity of the issue varies by region, with some states and distribution networks more constrained than others. According to Adalberto Vargas Ribeiro, director of Alba Energia, based in Colatina, Espírito Santo, the company first encountered these limitations in 2024, when local utility Santa Maria began carrying out simulation-based connection studies. The situation became more restrictive in 2025, when the utility started issuing connection assessments showing that feeders had already reached their capacity to absorb additional exported electricity. To address the challenge, Alba Energia recently completed two projects combining the Brazilian electricity regulator Aneel’s simultaneity rule, which exempts eligible projects from reverse power flow analysis, with smart power controllers. The approach enabled the installation of PV systems with capacities well above the utility’s authorized export limit at two rural consumer units, provided that any additional generation is consumed instantly on site rather than exported to the grid. Fast-track eligibility beyond 7.5 kW In 2024, Aneel introduced rules allowing reverse power flow assessments to be waived if specific technical requirements are met. One of these is the simultaneity criterion, which takes a consumer unit’s instantaneous electricity demand into account when determining the maximum amount of power that can be exported to the grid. The calculation is based on the previous 12 months of average consumption. “Consumers planning to increase their electricity consumption must wait up to 12 months for the higher demand profile to appear in the historical data used by the utility,” Ribeiro told pv magazine. “For irrigators, there is an additional limitation because the subsidized tariff encourages electricity use at night, while the simultaneity calculation only considers daytime consumption.” To overcome these constraints, Alba Energia began deploying smart power controllers. The devices continuously monitor PV generation and on-site electricity demand, automatically reducing inverter output whenever exported power approaches the utility-approved limit. When electricity is being consumed on site, however, the additional PV generation is directed to local loads instead of being curtailed. “The controller connects two scenarios,” Ribeiro said. “If the customer has a load, the electricity supplies the facility. If there is insufficient demand, it limits exports to the value authorized by the utility.” Off-grid systems are not suitable for every customer Ribeiro said interest in complete energy independence has increased in recent years but added that he generally does not recommend fully off-grid systems to his customers. “I always explain the costs and the realities of our region,” he said. “In Espírito Santo, for example, power outages are relatively infrequent. They do occur, but not often. Fully off-grid systems make more sense in regions where interruptions are more common.” He also noted that local utilities generally provide reliable service. “In our region, the main utilities are EDP and Santa Maria. Santa Maria serves around 11 municipalities and typically restores service very quickly. Even in more remote rural areas, outages are usually resolved within a short time,” he added. By contrast, he said, customers with off-grid systems depend entirely on the installer for technical support. “If an off-grid system fails, the customer depends on the installer having a 24-hour response team available. In some cases, the customer could be without electricity for longer than if they were connected to the utility grid,” Ribeiro emphasized. Pilot project One of the projects recently delivered by Alba, utilizing a simultaneity strategy combined with smart controllers, was installed at the Guisolphi family’s property—specialty coffee producers in São Roque do Canaã, Espírito Santo. Under simultaneity rules, the utility company authorized the export of only 7.5 kW to the grid. In a conventional project, this would also limit the inverter’s power rating. Since the family intended to expand production and bean processing, Alba Energia proposed a 37.2 kW plant equipped with a 23 kW inverter and a smart controller configured to restrict grid injection to the authorized 7.5 kW. In practice, when the property’s consumption is high, the inverter can operate at a power level well above the export limit. “If the property is consuming 15.5 kW, for example, the inverter can generate 23 kW. The 15.5 kW supplies local loads, and only 7.5 kW is exported to the grid,” explained Ribeiro. “The surplus energy turns into credits that the consumer unit itself can use for up to 60 months, maintaining savings even during nighttime consumption or periods of peak demand.” Daytime irrigation The second project was developed for the property of farmer Célio Marins Tatagiba. In this case, the challenge was different. The producer was using a special tariff for nighttime irrigation but wanted to shift operations to daytime hours to facilitate equipment maintenance and reduce nighttime labor costs. Since the historical daytime consumption was low, the utility company authorized an export limit of only 11 kW. Even so, Alba installed a 48.36 kW plant—comprising 78 modules rated at 620 W and three 10 kW inverters—once again utilizing an intelligent controller. “It made sense for the client,” said Ribeiro. “The generated power isn’t fed into the grid but instead powers the water pumps. That’s why the system appears undersized if you look only at the authorized export capacity, yet in practice, it meets the property’s entire load.” Beyond the power limitation, this project presented an additional challenge. Although controllers for “Zero-Grid” applications already existed, the solution available for split-phase grids could only control a single inverter. Since the project involved three units operating in parallel, a new configuration had to be developed. The solution involved a partnership between Alba Energia, the Chinese manufacturer GoodWe, and PHB, the brand’s distributor in Brazil. According to Ribeiro, GoodWe developed a specific software update allowing a single controller to simultaneously monitor all three inverters. PHB conducted laboratory tests prior to the final field deployment. “When we installed the system, we realized the controller still couldn’t manage all three inverters at once. GoodWe developed a software update, PHB validated everything in the lab, and then we performed the field configuration. That’s when it started working,” he stressed. While Ribeiro does not claim this was the first application of its kind in the country, he considers the solution to be relatively uncommon for split-phase grids. “This already existed for three-phase systems. However, controlling three single-phase inverters in parallel wasn’t an off-the-shelf solution. It turned into a success story because it required the development of a specific feature,” he said. A trend in response to grid constraints According to Ribeiro, the use of smart controllers is likely to become increasingly common as access constraints on distribution grids grow. “Today, for many customers who already have a power plant and need to increase their consumption, it is difficult to do so without this type of solution. The controller makes it possible to maintain the exact authorized export power while using all additional generation to meet local load demands,” Ribeiro concluded. According to Alba Energia, experience shows that export constraints do not necessarily spell the end of distributed generation expansion. Through real-time monitoring, smart power control, and system designs tailored to each customer’s consumption profile, it is possible to reconcile grid limitations with the expansion of photovoltaic systems. Please login to comment