A soft breeze is wafting across the fields of the Palatine municipality of Offenbach an der Queich. It sets the huge rotor blades of the six wind turbines operated by regional energy supplier EnergieSüdpfalz GmbH & Co KG into motion. Each year, they produce a total of 40 million kilowatt-hours for 13,800 households. The wind farm has a total output of 15.8 megawatts. A small concrete structure turns it into something special: The little building contains the first high-frequency filter system from MR, which ensures disruption-free grids at frequencies up to 9 kHz.