Fraunhofer ISE Unveils Groundbreaking Medium-Voltage String Inverter for Photovoltaics

Fraunhofer Institute for Solar Energy Systems ISE has achieved a groundbreaking milestone by developing and successfully deploying the world’s first medium-voltage string inverter designed for large-scale power plants. This achievement marks a significant advancement in photovoltaic (PV) technology, demonstrating the technical feasibility of handling higher voltage levels in PV systems.

The “MS-LeiKra” project team, in collaboration with Siemens and Sumida and funded by the German Federal Ministry for Economic Affairs and Climate Action, has created an inverter capable of raising the output voltage to the medium-voltage range of 1,500 VAC at 250 kVA. This innovation is made possible through the use of silicon carbide semiconductors, known for their higher blocking voltage, and a more efficient cooling concept using heat pipes, which reduces the need for aluminum.

One of the remarkable benefits of this achievement is the potential for substantial cost and resource savings in PV systems, particularly in terms of passive components and cables. For instance, higher voltage levels enable the use of thinner cables, significantly reducing copper consumption. At today’s output voltage of 800 VAC, a 250 kVA string inverter necessitates 120 mm² cables. However, by increasing the voltage to 1,500 VAC, the cable cross-section can be reduced to 35 mm², resulting in approximately 700 kilograms less copper per kilometer of cable.

This development has broader implications beyond PV, extending to applications like wind turbines, electric mobility, and industrial grids, where high-capacity systems require large cross-section cables. The success of the “MS-LeiKra” project opens doors for a new system concept that promises to revolutionize the next generation of large-scale PV power plants and has the potential to be applied across various sectors. The project team is now seeking partners in the field to test this innovative power plant concept.