TY - JOUR
T1 - A Closed-Loop Soft Startup Strategy to Suppress Inrush Current for Full-Bridge Modular Multilevel Converters
AU - Zhang, Debin
AU - Sha, Deshang
AU - Gao, Congzhe
AU - Liu, Xiao
AU - Long, Hanwen
AU - Tang, Guangshan
AU - Zhao, Yining
AU - Gao, Yang
N1 - Publisher Copyright:
© 1986-2012 IEEE.
PY - 2024
Y1 - 2024
N2 - Aim to charge all submodule (SM) capacitors of the full-bridge modular multilevel converter (FB-MMC) to their nominal voltage values smoothly and effectively, this article proposes a closed-loop soft startup strategy by utilizing the negative output voltage of FB-SM, which completely suppresses the potential inrush currents at the startup process. Based on the analysis of the precharging process of FB-MMC with load, when bypassing the current limiting resistors, the inrush currents are induced owing to the presence of load. To solve this issue, an improved startup strategy is further proposed by intentionally controlling the dc voltage to zero. With this strategy, the main ac contactor is closed with zero current, which is beneficial for extending the service life of mechanical switches. Besides, the overall control system is integrated and optimized because separately designed startup control is not required, thereby reducing the computational burden of digital controllers. Moreover, the SM capacitors can be charged rapidly by a ramp shaped charging current, and equal charging of all SMs during startup process can be guaranteed with the voltage balancing control algorithm. Simulation and experimental results of three-phase FB-MMC rectifier interfaced with grid and 5 kV dc are provided to validate the feasibility and effectiveness of the proposed startup strategy.
AB - Aim to charge all submodule (SM) capacitors of the full-bridge modular multilevel converter (FB-MMC) to their nominal voltage values smoothly and effectively, this article proposes a closed-loop soft startup strategy by utilizing the negative output voltage of FB-SM, which completely suppresses the potential inrush currents at the startup process. Based on the analysis of the precharging process of FB-MMC with load, when bypassing the current limiting resistors, the inrush currents are induced owing to the presence of load. To solve this issue, an improved startup strategy is further proposed by intentionally controlling the dc voltage to zero. With this strategy, the main ac contactor is closed with zero current, which is beneficial for extending the service life of mechanical switches. Besides, the overall control system is integrated and optimized because separately designed startup control is not required, thereby reducing the computational burden of digital controllers. Moreover, the SM capacitors can be charged rapidly by a ramp shaped charging current, and equal charging of all SMs during startup process can be guaranteed with the voltage balancing control algorithm. Simulation and experimental results of three-phase FB-MMC rectifier interfaced with grid and 5 kV dc are provided to validate the feasibility and effectiveness of the proposed startup strategy.
KW - Inrush current
KW - modular multilevel converter
KW - precharge
KW - soft-start strategy
UR - http://www.scopus.com/inward/record.url?scp=85200822088&partnerID=8YFLogxK
U2 - 10.1109/TPEL.2024.3436638
DO - 10.1109/TPEL.2024.3436638
M3 - Article
AN - SCOPUS:85200822088
SN - 0885-8993
VL - 39
SP - 14787
EP - 14799
JO - IEEE Transactions on Power Electronics
JF - IEEE Transactions on Power Electronics
IS - 11
ER -