TY - JOUR
T1 - Enhancing Light-power Efficiency and Achieving Wide-Range ZVS in MMC-Based DC Transformers by Varying AC-Link Voltage and Frequency
AU - Zhang, Debin
AU - Sha, Deshang
AU - Zhao, Yining
N1 - Publisher Copyright:
© 1986-2012 IEEE.
PY - 2025
Y1 - 2025
N2 - The modular multilevel converter based DC transformers (MMC-DCT) are becoming essential parts of medium voltage DC (MVDC) applications. The implementation of ZVS is necessary for MMC-DCT to achievehig her switching frequencies, there by improving power density and realizing light weight. However, with conventional phase shift (PS) control, the ZVS range is very narrow. To solve this issue, avariable ac-link voltages and frequency (VAVF) control strategy is proposed, which is achieved by adjusting the number of constantly inserted or by passed sub modules (SMs) with in a switching cycle. Meanwhile, the capacitor voltage-balancing algorithm is introduced. With this strategy, the ZVS range is extended over a wide power range. Moreover, since the switching loss of SMs and core loss of transformer are reduced, the efficiency of MMC-DCT is significantly improved at light power. Finally, the feasibility and effectiveness of the proposed control strategy is validated by experimental results.
AB - The modular multilevel converter based DC transformers (MMC-DCT) are becoming essential parts of medium voltage DC (MVDC) applications. The implementation of ZVS is necessary for MMC-DCT to achievehig her switching frequencies, there by improving power density and realizing light weight. However, with conventional phase shift (PS) control, the ZVS range is very narrow. To solve this issue, avariable ac-link voltages and frequency (VAVF) control strategy is proposed, which is achieved by adjusting the number of constantly inserted or by passed sub modules (SMs) with in a switching cycle. Meanwhile, the capacitor voltage-balancing algorithm is introduced. With this strategy, the ZVS range is extended over a wide power range. Moreover, since the switching loss of SMs and core loss of transformer are reduced, the efficiency of MMC-DCT is significantly improved at light power. Finally, the feasibility and effectiveness of the proposed control strategy is validated by experimental results.
KW - Modular multilevel converter (MMC)
KW - dc transformer (DCT)
KW - dual active bridge (DAB)
KW - zero-voltage switching (ZVS)
UR - https://www.scopus.com/pages/publications/105021436285
U2 - 10.1109/TPEL.2025.3631016
DO - 10.1109/TPEL.2025.3631016
M3 - Article
AN - SCOPUS:105021436285
SN - 0885-8993
JO - IEEE Transactions on Power Electronics
JF - IEEE Transactions on Power Electronics
ER -