Systematic identification and review of hybrid active filter topologies

Since the first installation of a passive tuned filter in the mid 1940s, the development of filter technology has advanced in incremental steps. The development of hybrid configurations to improve the performance of passive tuned filters has been quite ad hoc, building on the existing tuned links. This paper describes a process for systematically identifying all hybrid active filter topologies and their generalized characteristics. The paper first identifies generalised load categories which capture the dependence between harmonic voltage and current. The desirable attributes of filters for these loads are then discussed. The final step is to identify all possible combinations of active and passive elements and match these to the desirable attributes. The topologies are evaluated and those that offer significant advantages in rating are identified. The evaluation indicates those topologies that are known and those topologies that are relatively new.