Development of active filter with compensation for unbalanced three-phase voltages

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1. Producing of active filter with compensation for unbalanced three-phase voltagesAn of active filter with compensation for unbalanced three-phase voltages was produced. This system mainly consists of two circuits. One is an active filter circuit to compensate for current harmonics and the other is a compensator for unbalanced three-phase voltages. The former circuit is operated to synthesize currents which are antiphase with the load harmonic currents and the latter is operated to synthesize voltages which are antiphase with the negative sequence voltages of the source voltages.Thses circuits have only one energy storage capacitor in common. Therefore, this system needs lower capacity of the energy storage capacitor in comparison with other system which an active filter and an unbalanced voltage compensator are operated independently. In other words, we can make our active filter system compact.2. Steady state analysis of active filter circuitA set of 19 simultaneous differential cqu … More ations for an active filter circuit was derived and various waveforms of currents were calculated. The analytic results coincided with the experimental. Next, a passive filter to suppress the harmonic current generated by the PWM inverter of the active filter was designed with the analytic results. On basis of the analytic results, an active filter circuit with double current loops was proposed. By using these double current loops, both response of current control and stability of the system can be improved.3. Steady state analysis of active filter with compensation for unbalanced three-phase voltagesIn addition to the 19 differential equations in the section 2. , new 13 differential equations for the unbalanced voltage compensator were derived and various waveforms of both currents and voltages were calculated. The analytic results coincided with the experimental. In both analytic and experimental results, improvement in THD for the source corrents and in unbalance of the three-phase voltages was shown. Consequently, the availability of the proposed system was indicated. Less