Virtual two axes or orthogonal transformation technique instigated by Akagi in 1984 for
the investigation of the novel terminology of instantaneous power in three phase power systems and
extended by Dobrucky and Pokorny in 1999 for the determination of the instantaneous power in
single phase power systems, is utilised in this paper for the fast evaluation of the harmonic distortion
and reactive compensating currents in single phase shunt active power filters. Expressions for these
currents under different compensating conditions are derived in this paper. Control strategies are
utilised to implement these expressions. This results in providing excellent transient response of the
filter which is demonstrated experimentally. This fast dynamic response is achieved via the rapid
evaluation of the compensating current using a digital signal processor when the two axes strategy is
used
