Photovoltaic to high voltage inverter

By feeding power into the medium-voltage grid, the “MS-LeiKra” project team has demonstrated that PV inverters are technically capable of handling higher voltage levels. The benefits for photovoltaics in-clude enormous cost and resource savings for passive components and cables.

In the context of PV power plants, the "high-power" classification for multilevel inverters usually applies to systems operating in the MW range, incorporating medium voltage levels of 2.3–13.8 kV to optimize energy transmission efficiency and support reliable system performance .

To step up the output voltage of the inverter to such levels, a transformer is employed at its output. This facilitates further interconnections within the PV system before supplying power to the grid. The paper sets out various parameters associated with such transformers and the key performance indicators to be considered.

Higher voltage reduces the cable cross section. The inverter developed by Fraunhofer ISE enables the transition of PV from low voltage to medium voltage. Modern PV string inverters have an output voltage of between 400 V AC and 800 V AC. Although the output of power plants is steadily growing, voltage has not yet been increased.

The Fraunhofer Institute for Solar Energy Systems ISE has developed and suc-cessfully commissioned the world's first medium-voltage string inverter for large-scale power plants. By feeding power into the medium-voltage grid, the “MS-LeiKra” project team has demonstrated that PV inverters are technically capable of handling higher voltage levels.

Moreover, the inverters are interconnected in parallel with PV cells, facilitating power conversion in a singular-stage configuration. In the traditional structure of solar power plants, inverters and low-frequency transformers are utilized as an interface between PV panels and the AC grid for power transmission.