Capacitor Voltage Increment Suppression Control for CTB-HMMCs with Bypassed UFB-SMs Under DC Fault

• Published in: IEEE transactions on power electronics Vol. 38; no. 10; pp. 1 - 14
• Main Authors: Li, Qun, Deng, Fujin, Lin, Jinjiao, Chen, Shuangfeng, Yi, Haoran, Kong, Xiangping
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Achievement tests; Capacitors; Circuit faults; CTB-HMMC; dc faults; Direct current; Fault currents; faulty submodules; Hidden Markov models; Interruption; modular multilevel converters; power converter; protection; Short circuits; Switches; Thyristors; Voltage
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2023.3298791

The crossing thyristor branches (CTB) based hybrid modular multilevel converter (HMMC) can effectively protect high-voltage direct-current (HVDC) system under dc-line short-circuit fault with advantages of low percentage of unipolar full-bridge (UFB) submodules (SMs), short dc current interruption time and high efficiency. However, the faulty UFB-SMs being bypassed would affect dc fault current interruption performance of the CTB-HMMC, which may cause large capacitor voltage increment of UFB-SMs and deteriorate CTB-HMMC. This paper firstly analyzes the capacitor voltage increment of the CTB-HMMC with bypassed UFB-SMs under dc-line short-circuit fault. And then, this paper proposes a capacitor voltage increment suppression control (CVISC) for the CTB-HMMC with bypassed UFB-SMs under dc-line short-circuit fault, where the capacitor voltage increment of UFB-SMs during dc-line short-circuit fault can be significantly suppressed through bypassing suitable number of UFB-SMs according to the proportion of faulty UFB-SMs being bypassed in each arm, and therefore the proposed CVISC effectively protects the CTB-HMMC under dc-line short-circuit fault. The simulation and experiment are conducted, and their results verify the effectiveness of the proposed CVISC.