Active filters in HVDC systems: actual concepts and application experience

Active filters are frequently considered for HVDC systems because they provide superior harmonic performance and avoid problems which are often encountered in passive filter applications, like detuning, changes in the harmonic impedance of the network and resonance. This paper presents concepts actually regarded in the design of active filters for HVDC systems. Some installed AC and DC active filters, as well as relevant aspects related to the experience with these applications are presented. The aspect of control interactions among active filter is shortly discussed.