Germany’s Fraunhofer ISU Unveils Medium-Voltage String Inverter

The Fraunhofer Institute for Solar Energy Systems (ISE) in Germany  has achieved a pioneering feat by developing and deploying the world's first medium-voltage string inverter for large-scale solar power plants, known as the 'MS-LeiKra'.
 
This innovation showcases the technical capability of PV inverters to operate at higher voltage levels, beyond the typical range of 400 VAC to 800 VAC.
 
Traditionally, operational voltages in PV systems have remained limited due to the challenges associated with building highly efficient, compact inverters based on silicon semiconductors, and the absence of PV-specific standards covering higher voltage ranges.
 
Through a project funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) and in partnership with Siemens and Sumida, Fraunhofer ISE has developed an inverter capable of elevating the output voltage to the medium-voltage range (1,500 V) at 250 kVA.
 
This breakthrough technology harnesses silicon carbide semiconductors with superior blocking voltage and implements a more efficient cooling system using heat pipes, reducing the need for aluminum.
 
This achievement marks a significant milestone in the renewable energy sector, offering the potential for substantial cost and resource savings, particularly in passive components and cables within PV systems.
 
The medium-voltage string inverter concept lays the groundwork for the future of large-scale PV power plants, with potential applications in wind turbines, electric mobility, and industrial settings, contributing to more efficient, cost-effective, and sustainable power generation.