Resonance damping using Active Harmonic Filter

LOCATION: Munich, 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


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.

references gtk without filter

Picture: 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 P200-100 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.

Voltage harmonics kept well within the limits at all times ADF P200 (first generation) installed


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

Ralf Nosswitz quote

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Picture: Resonance after Active Dynamic Filter was installed


• 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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