The project, concluded with a final report dated 31 December 2023, set out to create a new system concept for the next generation of large photovoltaic (PV) power plants. The main technical goal was to raise the alternating‑current (AC) output voltage of string inverters from the current maximum of 800 VAC to a medium‑voltage level of at least 1 500 VAC. This increase is expected to deliver significant cost advantages by reducing copper consumption in the inverter modules and by allowing smaller cable cross‑sections, thereby lowering installation costs. Historically, the rise in inverter power has been accompanied by a rise in AC voltage—from an initial 300 VAC to the present 800 VAC—while the power per device has also increased. The new concept therefore pushes the limits of existing low‑voltage standards (VDE 0100, which covers up to 1 500 VDC and 1 000 VAC) and requires normative work under the emerging VDE 0101 framework for AC voltages above 1 000 VAC.
The technical work was organised into several work packages. In the requirement analysis phase (AP10) the team defined the performance targets and safety constraints for the high‑voltage system. The system concept (AP11) introduced a modular DC‑DC converter architecture that can be scaled to meet the 1 500 VAC requirement while maintaining high efficiency and reliability. Protection studies (AP12) examined fault isolation, over‑voltage, and resonance mitigation, recognising that the large number of parallel string inverters in a PV plant can excite resonances. Component testing and characterisation (AP20) validated the electrical and thermal performance of the new modules, while the DC‑DC converter development (AP23) produced a prototype that demonstrated the feasibility of the modular approach. Internal communication and control (AP30) and external interface design (AP31) ensured that the new inverters could be integrated into existing plant control architectures. Finally, system evaluation and demonstration (AP32) confirmed that the prototype met the target voltage, power density, and safety criteria in a laboratory setting.
Key performance figures reported include the successful operation of the prototype at 1 500 VAC AC output, a power density increase of roughly 20 % compared with conventional 800 VAC inverters, and a reduction in copper weight by about 15 %. The modular DC‑DC converter achieved an efficiency of 97 % at full load, and the protection scheme limited fault currents to below the design threshold, thereby safeguarding the plant’s electrical network. The demonstration also highlighted the reduced cable cross‑section requirement, translating into a projected installation cost saving of up to 10 % for large‑scale PV plants.
Collaboration was carried out within a consortium led by Siemens AG, a global leader in electrical engineering and electronics. The project partners included T PEL PEA‑DE and MS‑Leikra, which contributed expertise in power electronics design and system integration. The consortium worked over a multi‑year period, with the final report summarising the outcomes and outlining a plan for further development and potential industrial deployment. While the funding source is not explicitly stated in the report, the project aligns with German research priorities aimed at advancing renewable energy technologies and reducing the cost of photovoltaic installations. The consortium’s findings are intended to inform future standardisation efforts and to support the deployment of medium‑voltage PV plants in the coming decade.