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Geothermal power plant, Germany

SWM Services GmbH München is the public utilities company that supplies the city of Munich with electricity, natural gas, district heating and cooling, as well as fresh drinking water from the Bavarian Alpine foothills. At one of their geothermal plants used for power generation and district heating, the use of a large number of frequency converters was creating major problems that only a solution from Comsys could solve. Fortunately for SWM, our partner in Bavaria, PQ ENGINEERING, was there to help

Geothermal power plant in Germany

Location: Munich, Germany
Industry: Energy
Timeline: 2013


At their Sauerlach geothermal plant in Munich, thirty six frequency converters on a single transformer are used for the cooling units. Due to the high capacitive components of the load, a resonance point is formed in the network at the 25th harmonic. The resonance is so extreme that it was causing not only unusual noises, but also massive violations of EN 61000-2-4 class 2 limits, along with warranty issues for the supplier of the electrical equipment.

Resonance without Active Dynamic Filter installed Resonance without Active Dynamic Filter installed
Resonance without Active Dynamic Filter installed


After acceptance measurements carried out by PQ ENGINEERING revealed the limit value violations, a test installation with the active resonance damper Comsys ADF P200 was carried out. PQ ENGINEERING keeps these universal filters in stock for quick response to just such "emergencies". Targeted programming of the filter’s impedance enabled the increased harmonics in the area of the resonance point to be reduced to a permissible level. After the test installation was completed, ADF P200 filters were installed on both of the main distributors. No other supplier was able to offer an active controlled solution for resonance damping.

ADF P200 (first generation) installed


The solution completely dampened the resonance, thus eliminating the severe compliance issues. 

Resonance after Active Dynamic Filter was installed
Resonance after Active Dynamic Filter was installed

"Since commissioning, no power quality issues or equipment failures have been reported"

Ralf Nosswitz


Perfect resonance damping

  • Highly dynamic damping of the resonance point

  • Flexible use, even if the customer makes changes later

  • Easy retrofitting in the fully assembled switchgear

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