Transport Characteristics and AC Losses in YBCO Toroidal Coils for DC Reactor With Harmonic Current of Three-Phase Converter

In plant and industrial complex, further energy saving can be realized by DC interconnection between the ends of AC radial distribution system. We fabricated a power system simulator to verify that the DC interconnection is effective for energy saving in the distribution system. An YBCO toroidal coil composed of eight double pancake coils was fabricated and adopted in the simulator as a DC reactor. Harmonic current with DC-offset component were observed in the YBCO toroidal coil and the frequency component ratio of harmonic current depended on the inductance of the toroidal coil. Energy loss in the YBCO toroidal coil during the DC interconnection in the power system simulator decreased with the inductance of the YBCO toroidal coil because the magnitude of harmonic current component decreased with the inductance. To clarify the loss characteristics in the YBCO toroidal coil, we investigated influence of the magnitude of harmonic-frequency component and DC-offset component on the transport current loss in YBCO tape conductor. The transport current lose was independent of the magnitude of DC-offset component. The energy loss characteristics in the YBCO toroidal coil were closely related to the transport current loss in the YBCO tape conductor with harmonic current.