Voith has supplied its pumped storage technology for a 390MW Portuguese hydropower plant operated by Energias de Portugal (EDP) and named as Frades II.

In this regard, the technology group had delivered two variable speed pump turbines to meet the power capacity of the hydropower plant, located in Vieira do Minho.

It also supplied a couple of asynchronous motor-generators, each having an output of 440MVA along with hydraulic steel components, frequency converter and control systems.

Frades II is being touted to be the largest variable speed pumped storage plant in Europe and considered as the flagship project for similar kind of plants across the world.

Voith says that its generators unlike a traditional asynchronous generator have their rotational speed locked firmly to the line frequency of 50Hz. The mechanical speed of the generators can vary though as it is not tied to line frequency.

One advantage of Voith’s pumped storage technology is that it can make the hydropower plant to respond quicker and more flexibly to both the active and reactive demand from the electric grid.

Another advantage is the additional stability it offers in the case of a voltage drop. Thereby, it reduces the possibility of a power breakdown and allows for a fast restart even if there is a power outage.

Voith Hydro’s Thomas König who handles the Electrical Balance of Plant in Heidenheim, Germany said: “If the grid voltage drops to 5% of its normal value, the Frades II power plant can remain stable for 600 milliseconds, that is four times longer than conventional turbines with fixed speeds.

“In emergency situations this time difference can be crucial when there is a need to prevent a large-scale power outage.”

According to Voith, the Frades II pumped storage power plant contributes significantly in grid stabilization and also to support Portugal’s interest in growing its power generation from renewable sources.

Image: 3D model of the generator in the Frades II pumped storage power plant. Photo: courtesy of Voith.