Hiroaki Kakigano

Fundamental study on control strategies to increase efficiency of dual active bridge DC-DC converter

The dual-active-bridge (DAB) topology is ideally suited for bidirectional power transfer. However, the zero-voltage switching (ZVS) range of this topology is limited. Operating in ZVS mode can increase low range power transfer. This paper revised and simplified calculation of ZVS range for single pulse-width modulation (SPWM) and dual pulse-width modulation (DPWM) controls, and power transfer for different winding ratio. These control strategies are compared, combined, and manipulated by three variables: the phase shift between the primary and secondary transformer voltages, the primary voltage width, and secondary voltage width. Combination of these control strategies can reduce the power loss especially in lower range power transfer. A 6 kW, 40 kHz bidirectional isolated dc-dc converter between was simulated to validate the theoretical ZVS range and power transfer.

DC capacitor voltage regulation of modular multilevel cascade converter (MMCC-SSBC) for DC-powered data center

DC 380 V power supply has begun to be used for data centers to save energy and supply high quality power. This paper describes dc capacitor voltage regulation of ac-dc converter using Modular Multilevel Cascade Converters based on Single-Star Bridge-Cells (MMCC-SSBC) without line frequency transformer. The proposed voltage regulation method compares each dc capacitor voltage with the reference value directly. The numerical simulations demonstrated the validity of the control even when 3-phase power consumptions are unbalanced.

Guest Editorial: Special Section on Smart DC Distribution Systems

This special section on smart DC distribution system includes the following topics: control of DC microgrids; stability assessment and remedies for DC distribution systems; low voltage DC distribution utility sites; protection issues in DC distribution networks; and optimization, energy management, and demand response paradigms.