Active filter used as a controlled reactance to prevent harmonic resonance in interconnected offshore power systems

Harmonic resonance is of particular concern in the design and operation of interconnected offshore power systems. This paper shows that it is possible to attenuate such resonance using an active filter. A new control method is proposed which can assess the system condition from a harmonic point of view and take into account the relative distribution of exciting frequencies and system resonant modes. Measured system busbar voltage is the only feedback required by the filter controller and the power system condition is initially unknown and variable. A series of time domain simulation results are presented to illustrate the effectiveness and limitations of the 'active harmonic damper' while some practical design considerations are highlighted.