TY - JOUR
T1 - A Generalized Precharging Strategy for Soft Startup Process of the Modular Multilevel Converter-Based HVDC Systems
AU - Zhang, Lei
AU - Qin, Jiangchao
AU - Wu, Xiajie
AU - Debnath, Suman
AU - Saeedifard, Maryam
N1 - Publisher Copyright:
© 1972-2012 IEEE.
PY - 2017/11/1
Y1 - 2017/11/1
N2 - The modular multilevel converter (MMC) has become the most attractive converter technology for medium/high-power applications, specifically for high-voltage dc (HVdc) transmission systems. One of the technical challenges associated with the operation and control of the MMC-based system is to precharge the submodule (SM) capacitors to their nominal voltage during the startup process. In this paper, considering various SM circuits, a generalized precharging strategy is proposed for the MMC-based systems, which can implement soft startup from the dc or ac side. The proposed precharging strategy can be applicable for various SM circuits and MMC configurations. The proposed startup strategy does not require extra measurements and/or auxiliary power supplies. The charging current is controlled by adjusting the changing rate of the number of blocked and bypassed SM capacitors. Based on the proposed startup strategy, the startup processes of MMC/MMC-HVdc systems with various SM circuits are analyzed and a generalized startup procedure for various MMC-HVdc systems is proposed. In addition, the uncontrollable steady-state SM capacitor voltages of various MMC-based systems are analyzed and the associated precharging time is also investigated. Performance of the proposed strategy for various MMC-HVdc systems is evaluated based on time-domain simulation studies in the PSCAD/EMTDC software environment and experimental results are based on a scaled-down prototype.
AB - The modular multilevel converter (MMC) has become the most attractive converter technology for medium/high-power applications, specifically for high-voltage dc (HVdc) transmission systems. One of the technical challenges associated with the operation and control of the MMC-based system is to precharge the submodule (SM) capacitors to their nominal voltage during the startup process. In this paper, considering various SM circuits, a generalized precharging strategy is proposed for the MMC-based systems, which can implement soft startup from the dc or ac side. The proposed precharging strategy can be applicable for various SM circuits and MMC configurations. The proposed startup strategy does not require extra measurements and/or auxiliary power supplies. The charging current is controlled by adjusting the changing rate of the number of blocked and bypassed SM capacitors. Based on the proposed startup strategy, the startup processes of MMC/MMC-HVdc systems with various SM circuits are analyzed and a generalized startup procedure for various MMC-HVdc systems is proposed. In addition, the uncontrollable steady-state SM capacitor voltages of various MMC-based systems are analyzed and the associated precharging time is also investigated. Performance of the proposed strategy for various MMC-HVdc systems is evaluated based on time-domain simulation studies in the PSCAD/EMTDC software environment and experimental results are based on a scaled-down prototype.
KW - High voltage dc (HVdc)
KW - modular multilevel converter (MMC)
KW - precharging the submodule (SM) capacitors
KW - soft startup precharging process
UR - http://www.scopus.com/inward/record.url?scp=85028887900&partnerID=8YFLogxK
U2 - 10.1109/TIA.2017.2736958
DO - 10.1109/TIA.2017.2736958
M3 - Article
AN - SCOPUS:85028887900
SN - 0093-9994
VL - 53
SP - 5645
EP - 5657
JO - IEEE Transactions on Industry Applications
JF - IEEE Transactions on Industry Applications
IS - 6
M1 - 8003320
ER -
