Capacitor Size Comparison on High-Power DC-DC Converters with Different Transformer Winding Configurations on the AC-link

This paper compares the capacitor requirement of the modular multi-level converter based dual-active-bridge (MMC-DAB) and the controlled transition bridge based dual-active-bridge (CTB-DAB) DC-DC converters. Three winding configurations, namely YY, DD, and YD, are considered for the AC-link\u27s medium-frequency transformer (MFT). It is shown that for a specific inverter topology (i.e., MMC or CTB), the YY and DD connections of the MFT results in identical energy storage requirements for the converters. Moreover, it is demonstrated that the YD connection reduces the capacitor requirements of the converters considerably. In the best case, the capacitor requirement can be reduced for the MMC-DAB and the CTB-DAB by 30% and 40%, respectively. A comparison between the converters showed that the YY-connected MMC-DAB (the YD-connected CTB-DAB) has the highest (the lowest) energy storage requirement. Additionally, it is shown that the YD-connected CTB-DAB can achieve up to 78% (58%) less energy storage compared to the YY-connected MMC-DAB in the best case (worst case)

Capacitor and Switch Size Comparisons on High-Power Medium-Voltage DC-DC Converters with Three-Phase Medium-Frequency Transformer

This paper compares the capacitor requirement of\ua0selected isolated DC-DC converters for high-power and medium-voltage applications. A numerical comparison is made for a range\ua0of switching frequencies and transition times, considering not\ua0only the sub-module capacitors of the converters but also the\ua0DC-link capacitors. Likewise, a comparison regarding the semiconductor requirement is performed for the converters. Selected\ua0inverter topologies to form the dual-active-bridge (DAB) DCDC converter include the two-level converter (2LC), the modular\ua0multi-level converter (MMC), the transition arm converter (TAC),\ua0the modular transition arm converter (MTAC), and the controlled\ua0transition bridge converter (CTB). The results show that conventional DAB requires the minimum capacitor size among\ua0the converters. Moreover, in the appropriate operation region,\ua0the MTAC-DAB and the CTB-DAB provide the possibility of up\ua0to 40% and 60% reduction in the amount of required energy\ua0storage compared to the MMC-DAB, respectively. It is also\ua0shown that the size of the DC-link capacitors become comparable\ua0with the chain-links’ capacitors when the percentage of the\ua0transition times per period is reduced to be below 5%. The\ua0comparison regarding the semiconductor requirement revealed\ua0that the MMC-DAB requires the smallest installed switch power\ua0among the multi-level converters

Hybrid alternate-common-arm converter with high power capability : Potential and limitations

This paper studies a new hybrid converter thatutilizes thyristors and full-bridge (FB) arms for achieving higherpower capability than the full-bridge (FB) modular multilevel converter (MMC) with reduced semiconductor requirements. The study covers the theoretical analysis of the energy balancing,the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of theconverter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the design constraints that need to be fulfilled for achieving the maximum power capabilityof the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors andthe power angle. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed.QC 20191018</p

Feasibility and Safety of Repeated Carbon Ion Radiotherapy for Locally Advanced Unresectable Pancreatic Cancer

Purpose: The feasibility and safety of re-irradiation with carbon ion beams for locally recurrent unresectable pancreatic cancer (URPC) after carbon ion radiotherapy (CIRT) was evaluated. Methods: Medical records from patients with re-irradiated URPC who were treated with CIRT between November 2017 and February 2019 were reviewed. Inclusion criteria were (1) isolated local recurrence after CIRT, (2) URPC, and (3) tumor located at least 3 mm from the gastrointestinal tract. The first and second CIRT irradiation doses were 55.2 Gy (relative biological effectiveness) in 12 fractions. Results: Ten patients met the inclusion criteria. The median follow-up period was 25.5 months (range, 16.0–69.1) after the first CIRT and 8.9 months (range, 6.4–18.9) after the second CIRT. The median interval between the initial CIRT and the local recurrence was 15.8 months (range, 8.0–50.1). One patient developed grade 3 diarrhea immediately after the second CIRT; no other grade 3 or higher adverse events were attributed to CIRT. The estimated 1-year overall survival, local control, and progression-free survival rates after the second CIRT were 48%, 67%, and 34%, respectively. Conclusion: Repeated CIRT is feasible with acceptable toxicity for selected patients with locally advanced URPC after CIRT