Active filter functionalities for power converters in wind power plants

The project intends to analyse and develop advanced filter solutions based on combinations of passive filters and active filters. The use of passive filters is almost standard for harmonic mitigation; therefore, the primary focus is to develop active filter solutions. For the active power filters, the power electronic converters already present in the WPP and static compensator (STATCOM) will be used as much as possible. Emphasis will be given to the capability of retuning these filters online or at least with a minimum downtime, so as to cope with the continuously changing scenario of the network harmonic composition and resonance possibilities.

The project will start with a focussed review of the relevant harmonic sources and their interactions in large offshore wind power plants. The harmonic impedance characterization of the network is necessary to ensure proper harmonic mitigation plan. An analysis part will be included concerning the harmonic problems in WPPs, especially with respect to the problems concerning series and parallel resonances and grid code compliance. The final objective is to have an optimized combination of active and passive filter. At present the harmonic mitigation is mainly achieved by large passive filters in the wind turbines and at the grid connection substation. In addition to reviewing this approach, use of active filters either in combination with the existing and/or new passive filters will be investigated.