This paper describes configuration and operation of a high-frequency link resonant inverter using cycloconverter techniques. In this inverter, a resonant link high-frequency voltage generated in a primary resonant inverter is isolated by a high-frequency transformer, then directly converted into a resonant link low-frequency voltage in a cycloconverter. The switching losses and surge voltage levels can be reduced by making all switches in the primary inverter and the cycloconverter operate at zero voltage. The relationship between characteristic impedance of the resonant circuit and the conversion efficiency, and the distortion factor characteristics of the output voltage waveforms are discussed by comparing of analytical and experimental results.

Stand-alone photovoltaic (PV) power systems are potential power sources for telecommunications equipment especially equipment installed outdoors. To be practical, they must have a high conversion efficiency and a long lifetime. We have proposed a stand-alone photovoltaic power system that uses electric double-layer capacitors (EDLCs) and lead acid batteries as power storage devices. This system smooths out the fluctuations in power generated by the PV array by using the EDLC's charge-and-discharge power; this reduces the number of battery charge-and-discharge cycles. We simulated the system's operating characteristics and evaluated the photovoltaic array mismatching loss, system conversion loss, battery contribution factor, averaged battery state-of-charging, and maximum depth-of-discharging. The results show that the system is effective at reducing the mismatching loss and battery contribution factor, so the system efficiency is expected to be improved by using high conversion efficiency DC-DC converters. Moreover the system can maintain the averaged battery state-of-charging during operation. This indicates that smaller batteries can be used. The maximum depth-of-discharging can be kept lower than in the conventional system. Consequently, the proposed system should have a longer battery lifetime.

High efficiency power feeding systems are effective solutions for reducing the ICT power consumption with reducing power consumption of the ICT equipment and cooling systems. A higher voltage direct current (HVDC) power feeding system prototype was produced. This system is composed of a rectifier equipment, power distribution unit, batteries, and the ICT equipment. The configuration is similar to a -48 V DC power supply system. The output of the rectifier equipment is 100 kW, and the output voltage is 401.4 V. This paper present the configuration of the HVDC power feeding system and discuss its basic characteristics in the prototype system.