The principle objective of this research effort is to develop design procedure for active filters to improve power quality. A comprehensive design procedure for active power filter was derived from first principles, implemented in an advanced simulation software suite, verified against published data, and applied to several power systems. The active power filter model was represented by the average model in rotating dq- coordinates and synchronized with the input voltage, suitable for any power system level.

Active power filter transfer functions were developed and accurately predicted by instantaneous active power theory, d-q transformation, and dc small signal linearization. The steady-state characteristics of the average model in addition to the dynamic response characteristics (harmonic currents and reactive power and output voltage of the active filter), were verified against published data and accurately reflected system performance Control strategies were developed and steady state goals were achieved in controlling power factor and sinusoidal fundamental current waveforms. The results show that the converter has a fast dynamic response, ease of control and good switching pattern. This robust, system model is applied to a distribution power system and an electric ship power system. This design procedure of APF model can be applied to a wide variety of hybrid parallel active filters and multi module parallel active filters.