Managing electricity in a grid powered by renewable energy

The sun is shining, and not a single cloud can be seen in the blue sky in Brindisi, a town in Salento, sometimes described as the "heel" of the Italian "boot." Nearby, at a distribution substation in Mesagne, the world’s first hybrid transformer has been successfully commissioned. Set against the scenic backdrop of the ancient Via Appia, surrounded by olive groves and Baroque architecture, Enel and Hitachi Energy have piloted a pioneering 250 kW installation. This joint initiative exemplifies how innovative technology can enable smarter electricity management in a world increasingly powered by renewables. This is particularly interesting for Brindisi and its peri-urban area, where the total installed power capacity of the small solar plants matches the installed power of the loads.

But the sun doesn’t always shine – not even in Brindisi. At night, no energy is fed into the grid, while energy input is highest at midday. This can lead to grid overloads, voltage instability, and reverse power flows. Distribution grids can respond to this challenge in two ways: They can either add capacity by constructing new lines and substations, which takes years from planning to execution. Or they can implement devices that optimize the utilization of existing infrastructure, thus boosting power throughput. This is where Hitachi Energy’s hybrid transformer comes in.

The hybrid transformer addresses today’s grid challenges by combining a conventional transformer with a smart layer of power electronics. It’s like upgrading a basic thermostat to a smart home system – it doesn’t just react; it adapts.

The hybrid transformer brings several advanced features into one compact solution:

• Dynamic voltage regulation: Keeps voltage levels stable, even when renewable generation and load power fluctuate rapidly and across the entire range. This is crucial in peri-urban areas like Brindisi, where solar generation can match or exceed local demand.
• Power factor correction: Improves energy efficiency by reducing the reactive (wasted) power that doesn’t contribute to useful work – similar to tuning a car engine for better mileage
• Phase load balancing: In a three-phase system, uneven loads can cause inefficiencies and overheating. The hybrid transformer can detect and correct these imbalances in real-time – like a traffic officer redirecting cars to keep all lanes equally used and flowing smoothly.
• Harmonic filtering: Cleans up electrical “noise” caused by modern devices, improving power quality and protecting sensitive equipment.

By integrating power electronics and inverter technology, electrical parameters can be precisely controlled, service quality is improved, and most importantly, grid capacity is increased, accommodating the integration of energy produced by renewable sources. In other words, the hybrid transformer makes the grid safer, more flexible, and stable. 

Enel and Hitachi Energy initiated the collaboration on this pilot transformer as a result of a contract awarded in 2023. While Enel contributed its expertise and network, Hitachi Energy’s R&D team assembled and tested the prototype at the factory in Lodz, Poland. This achievement is the culmination of a continuous effort spanning two years, led by the Hitachi Energy Transformers Business Unit’s R&D PE program, with the team distributed across Switzerland and Poland. The design phase was carried out in Geneva, Switzerland.

In the summer of 2025, the innovative transformer was installed in Mesagne, and its ability to dynamically regulate voltage and correct power factor has been confirmed in the field through live measurements and collected measurement logs during commissioning. It is a perfect illustration that we achieve more together and that it takes collaboration and partnerships to make the energy transition happen. 

The hybrid transformer isn’t just a technical upgrade – it’s a strategic asset. By providing flexibility, it allows distribution system operators to unlock up to 30 percent more capacity from the existing infrastructure, enabling a faster response to support the increasing amounts of renewable energy integrated into the grid. It represents a new class of digital grid equipment, multifunctional, adaptive, and designed to facilitate the energy transition. It can replace or complement devices, offering a more integrated and cost-effective solution.

As we continue testing and refining the technology, the hybrid transformer could become a cornerstone of modern distribution networks – enabling cleaner, more resilient, and more efficient energy systems.