Active Filter Functionalities for Power Converters in Wind Power Plants

Project Description

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.

Research Plan

The plan of this project is structured into 5 work packages:

  • WP 1: State-of-the Art Wind farm harmonic analysis
  • WP 2: Mitigation of harmonics by optimal use of active filter components
  • WP 3: Addition of harmonic filter and resonance damping functionality to the WTG power converters and FACTS devices
  • WP 4: Laboratory scale demonstration of Active filter implementation on parallel grid connected inverters
  • WP 5: Full scale demonstration of active filters at a wind power plant

Key Methods

Starting with a focussed review of the harmonic resonance issues and their prevalent mitigation plans in the wind power plants using the passive filters, the possibility of using active power filter techniques will be explored. Subsequently, the active power filtering technique will be applied on the existing power converters in the wind power plants and the FACTS devices like the STATCOM which are already present in the WPPs. The impact on the converter ratings and stress levels will be evaluated. The proposed concept will be demonstrated through a lab prototype comprising of multiple small inverters connected to a common ac grid in close proximity. Finally, a full scale demonstration is a real wind power plant will be attempted.


Professor Remus Teodorescu
Direct phone: +45 9240 9249

The project is granted from under The Forsk-EL programme

Project period: 2014 - 2016

Host Institution: Aalborg University

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