Evaluation of a shunt active filter using frequency identification

In general every electrical consumer connected to a power distribution network-be it single-phase, three-phase, AC or DC-should be supplied by a voltage quality that allows him to perform his functions without any disturbances caused by the supplying network. On the other hand the consumer should reduce the system perturbations produced by himself so far that no other consumers or installations are disturbed. This holds true for utility grids as well as for railway power supply. Nowadays consumers connected to utility grids as well as railway power supplies often cause undesired oscillations. The frequencies of these oscillations may be integral multiples of the base frequency (so-called harmonics), but often they are not (so-called interharmonics). If quantities of such loads are to be analysed in the frequency domain, for example to evaluate the advantages and disturbances caused by an active filter, interharmonics cause problems. This paper evaluates a shunt active filter using a frequency identification method, which in many cases solves the analysis problems caused by interharmonics.