A series resonant converter (SRC) operating as a DC transformer (DCX) is a candidate for the isolated bidirectional DC/DC converters of solid-state transformers (SSTs). However, the input/output current ripple of the SRC is relatively high, which requires bulky parallel capacitors and low-pass filters such as C/LC filters. These additional components reduce the power density. In addition, to operate an SRC as a DCX, a small resonant inductance is desired to reduce the voltage gain variation and achieve a faster transient response. To resolve these problems, a SRC with embedded filters is studied. Adding a clamping capacitor between split transformers not only significantly reduces current ripples and the harmonic components of the input/output currents but also connects resonant inductors in parallel to reduce the equivalent resonant inductance. In addition, dividing the resonant current into two split windings reduces the RMS current of the transformer. This paper presents a detailed analysis, a design methodology, and a comprehensive comparison with the conventional half-bridge CLLC converter with C/LC filters. 1-kW prototypes with a 600-V input voltage and 200-V output voltage demonstrate the superiority of the proposed converter; the second harmonic of the output current was significantly suppressed by 19.3 dB compared with that of the conventional converter with the same power density. The loss breakdown showed the proposed converter mitigated copper loss by 9.47% and eliminated the losses of the filter and DC-link capacitors. The prototype of the proposed converter had the highest efficiency of 95.4% at full-load among prototypes.

A high voltage bidirectional DC/DC converter is necessary for interconnecting a medium voltage (MV) DC network to a low voltage DC network in future DC power distribution networks. Several multilevel converter topologies have been investigated to handle the high voltage stress on the MV network, including a diode/capacitor clamped converter, a modular multilevel converter, and a cascaded H-bridge converter. However, these converters face the problem of voltage imbalance. In this study, a novel bidirectional isolated hybrid ripple-cancel dual active bridge (HRCDAB) converter for high voltage applications is developed. The proposed converter inherits the cancellation of the high-frequency ripple of DC-link capacitors, zero-voltage switching (ZVS), elimination of the DC bias current of the transformer, and automatic voltage and current sharing between stacked semiconductors. The circuit operation and certain features of the proposed circuit are comprehensively analyzed in this paper. Moreover, the design methodology of the proposed converter is presented. A scaled-down 900-V/600-V/1.2-kW prototype of the proposed converter is fabricated to experimentally demonstrate the validity of the comprehensive operation analysis and design theory.

Corresponding to diverse consumer needs, high-mix and low-volume production is becoming more important. Unique products matching consumer's sensitiveness tend to be welcome. These products will be something like art and craft products, which require skill and experience to create. This study deals with 5-axis control tool path generation to dexterously and efficiently create such craft-like microshapes, while maintaining the quality. Concerning 5-axis control machining, the way of using ball end mills is generally employed. However, it needs a lot of time to get high quality surface. To solve this problem, a side cutting edge of the ball end mill is positively utilized with its tool axis parallel to the ruled surface. Therefore, a new CAM system is developed to detect the surface to be machined with the side cutting edge, and to generate the collision-free tool paths between the tool and the workpiece. The effectiveness of the developed CAM system is experimentally confirmed by creating a tiny Möbius ring.

No abstract

This study deals with 5-axis control tool path generation to create microshapes dexterously and efficiently, while maintaining quality. Concerning 5-axis control machining, the use of ball end mills is generally employed. However, this method needs a lot of time to obtain high quality surface. To solve this problem, a side cutting edge of the ball end mill is positively utilized with its parallel to the ruled surface. Therefore, a new CAM system is developed to detect the surface to be machined with the side cutting edge, and to generate collision-free tool paths between the tool and the work piece. The effectiveness of the developed CAM system is experimentally confirmed by creating a tiny Möbius ring.