Active Filtering by Siemens Gamesa

Active Filtering (AF) is a control feature of the wind turbine converters, that is solving the problem of voltage harmonic distortion in offshore wind power plants (WPPs). Since all the offshore WPPs must comply with the Grid Codes, the developers have previously been forced to invest into the massive and expensive hardware filters, which occupy a lot of precious space at the offshore substation.

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AF technology does not require any additional hardware to what the turbine already has and it eliminates the need of using a hardware filter. The AF is based on a converter control loop, that modifies the PWM signal, reducing harmonics without affecting any other performance parameters.


  • Around EUR 10’000’000 saving per wind farm purely on hardware, by phasing out the hardware filter.
  • Valuable space is saved on offshore substation, thus reducing its cost.
  • Full flexibility – the Active Filter can be retuned at any stage of the project lifecycle.

How will this innovation contribute to the industry?

Besides reducing LCoE, the innovation is opening a lot of opportunities due to its flexibility. The WPP developers and turbine manufacturers are no more restricted by their preliminary designs, since the harmonic filters can be adjusted on any stage, thus compensating for any layout change. Developers will dodge in-compliance penalties, lost production and the need to procure the filters last-moment.