Recently, many energy-saving household appliances such as air conditioners, refrigerators, and LED bulbs are being used in residences. Most household appliances use diode rectifiers equipped with smoothing dc capacitors, which cause the passage of a large harmonic current through utility lines. This harmonic current may cause electrical equipment to malfunction or fail. Because the household appliances are connected to the single-phase utility grid, the third-harmonic component is dominant among the harmonic current generated by the appliances. However, the fifth-harmonic component generally is dominant in distortion contained by the utility voltage of power distribution lines. This paper discusses the flow of the third-harmonic current in three-phase three-wire system. As a result, if only the one conventional single-phase active filter is connected to the distribution system, the third-harmonic current may increase in the system. To solve this issue, the authors propose a control strategy of single-phase active filters. Furthermore, the validity of the proposed control strategy is shown by the experiment and simulation results.
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