Fraunhofer Develops First Medium-Voltage Solar Plants With 3 kV String Inverters

Solar is expected to add around 73 terawatts (TW) of new photovoltaic capacity by 2050, which will require large quantities of raw materials, including copper and aluminum. New research by Fraunhofer found a correlation between resource requirements and investment costs. It noted that investment cost can be significantly reduced if the PV system voltage level is raised to medium voltage. 

The “PVgoesMV” project aims to demonstrate, through the construction and operation of two pilot plants, that this step is technically feasible and economically viable for large-scale PV plants. These are the world's first PV plants with a 3 kV string inverter. Additionally, it noted support from all key system components manufacturers for the PV park project, which is scheduled to run for three years. The project, which started in December 2025, is funded by the German Federal Ministry for Economic Affairs and Energy as part of the 8th Energy Research Program “Innovations for the Energy Transition.”

Two Pilot Plants With 3kV Medium Voltage

The objectives of the project are to construct and test two pilot plants in Baden-Württemberg and Rhineland-Palatinate with a connected load of approximately 135 kilowatts over a period of several months. 

They will be operated at 3 kV on the DC side and 1.2 kV on the AC side. The medium-voltage PV inverter used, based on high-blocking silicon carbide semiconductors, was already developed by Fraunhofer ISE in the MS-Leikra project and is being adapted for use in the field. 

Two String Connections Are Being Tested in the project: 

On the one hand, the use of standard solar modules with 1500 V and center point grounding. Secondly, a 3 kV string with PV module prototypes was developed for the higher voltage class. Based on their experience in planning, construction, and commissioning, the project partners ultimately want to develop a quality assurance and testing concept for medium-voltage PV systems, incorporate findings from the field into their product design, and contribute to international standardization committees.

The project partners of “PVgoesMV” are Pfalzwerke AG, the FEAG Group, Stäubli Electrical Connectors AG, Weidmüller Interface GmbH & Co. KG, Mersen Deutschland Eggolsheim GmbH, Prysmian Kabel und Systeme GmbH, Sumida Components & Modules GmbH, Hanwha Q Cells GmbH, Zimmermann PV-Steel Group GmbH & Co. KG, Infineon Technologies AG, Fluke Deutschland GmbH, and BES new energy GmbH. They support the project by providing and further developing key components, as well as with expertise and engineering services for setup, commissioning, and monitoring.