Akinobu OKUI, Sigeo KAGA, Haruo IKEDA
Recently, a large capacity conversion system is used in a train, for frequency conversion and for DC power transmission. In such large capacity conversion systems, a harmonics of DC-link sometimes becomes a problem. This is because each converter has a capacitor on the DC-link, and DC circuit has a inductance. In general, if the harmonic resonance occurs at DC-link, then a filter or capacitor is added to DC-link. However, in VVVF inverter system, at DC-link, the frequency of harmonics current of the inverter varies, with the output frequency of the inverter. Therefore, by merely changing the frequencies of harmonics resonance at DC-link to other frequency by the filter and the capacitor, it would be impossible to avoid the harmonic resonance. First, this paper, describes a harmonic resonance which occurs at DC-link of a power conversion system for driving the linear synchronus motor (LSM). Second, it shows how it is possible to suppress the harmonic resonance by connecting an active filter to the DC-link. Third, the characteristics of DC-current of the active filter is analyzed. Lastly, it reports on experimental results of using a small model.