Active power filter with optimal servo controller

This paper presents a reduction method of higher harmonic currents using an active filter at the AC side of a condenser input-type three-phase diode bridge rectifier. As an active filter, a three-phase PWM inverter is connected in parallel to rectifier. The principle of the active filter is to cancel higher harmonic currents contained in load current by injecting reversed phase harmonic currents into the power source side. In this system, an optimal digital servo controller with dead time compensation is used to reduce the higher harmonics at the current controller. The root locus method and the simulation are used to obtain optimal weighting factor of a performance criterion and to select the control method. Finally, power spectra of a load side current and a source side one are shown. Experimental results are shown to verify the usefulness of this system.