Brazil has been experiencing a veritable solar boom for over a decade. Since the introduction of the net metering programme ‘Geração Distribuída’, the share of solar power has been growing. The 2012 legislation allows households and businesses to feed the energy they generate into the local power grid. In return, they receive credits on their electricity bills. Thanks to this and other support measures, as well as falling photovoltaic costs, decentralized solar energy has developed rapidly in South America's largest economy and, according to calculations by Absolar, the Brazilian association for photovoltaic solar energy, has already reached more than 36 gigawatts of installed capacity in the decentralised sector.

As in the rest of the world, Brazilian distribution grids are unidirectional and therefore not designed to accommodate large amounts of volatile solar power. But this is precisely where private households and many companies feed in their solar power into the grid. The consequence of an increasing number of decentralised producers: voltage fluctuations, overloads and violations of the voltage band.

Minas Gerais has also been greatly affected by this development. The state in the south-east of the country has a population of around 21 million and is considered the economic heart of Brazil. Mining, steel, and automotive industries are driving economic growth and energy demand. The responsible grid operator CEMIG, one of South America’s largest utilities, now has 4.2 gigawatts of installed PV capacity – most of it in small systems on rooftops and company buildings. Many distribution grids are already reaching their limits.

Maintaining power quality with increasing amounts of PV power being fed to the distribution grids is a key task for those responsible at CEMIG. They must prepare a grid with around 970,000 distribution transformers, which was designed for conventional generation, for a decentralized future. In addition to the high solar potential, weather fluctuations and intermittent cloud cover further impair the consistency of power generation. Therefore, there is  a great need in many distribution networks for control systems that can manage bidirectional energy flows. According to Marcelo da Costa, Managing Director of Reinhausen Brazil, studies and field analyses have shown that the voltage regulating distribution transformer (VRDT) does exactly that: under certain conditions, it can increase the absorption capacity of local networks by up to 50 per cent.

CEMIG is currently testing Reinhausen technology in two pilot projects and has selected two completely different supply areas for this purpose: one in Uberaba, a bustling city in the south-west of Minas Gerais. There, private PV systems on the roofs of private homes are putting strain on the voltage band. The Brazilian utility installed another VRDT in rural Bocaiúva, where it supplies a commercial customer who feeds PV power into the grid.

The previous transformers were replaced by VRDTs with ECOTAP® VPD® III, manufactured by transformer manufacturer Trael. According to CEMIG, installation was quick and integration into the existing grid went smoothly. CEMIG officials see the greatest potential at grid points with strong fluctuations due to PV feed-in. This is precisely where the new technology proves to be particularly effective.