Grounded Thyristor Loop-Based Hybrid MMCs for Valve-Side Single-Phase-to-Ground Faults in Bipolar HVdc Systems

• Published in: IEEE transactions on power electronics Vol. 39; no. 5; pp. 6298 - 6311
• Main Authors: Li, Huailong, Deng, Fujin, Tian, Jie, Lu, Yu, Li, Gang, Lin, Jinjiao
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bipolar high-voltage direct-current (HVdc); CAD; Capacitors; Circuit faults; Computer aided design; Electric power systems; Faults; Hidden Markov models; HVDC transmission; Inductors; modular multilevel converters (MMCs); Overcurrent; single-phase faults; Switches; thyristor; thyristor branch; Thyristors; valve-side faults; Voltage control
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2024.3368507

The valve-side single-phase-to-ground (SPG) fault is one of the key challenges for the MMC-based bipolar HVdc system. In this article, a grounded thyristor loop (GTL)-based hybrid MMC (HMMC) is proposed to protect the bipolar HVdc system under valve-side SPG faults. In the GTL-HMMC, the thyristor branches are proposed to connect the different arm inductors and the ground. The operation for the GTL-HMMC in case of valve-side SPG faults is also proposed, where the GTL-HMMC can handle the faults with the advantages of short-fault current interruption time, low capacitor overvoltage, low arm overcurrent, low semiconductor cost, and low power loss. Electromagnetic transient (EMT) simulation studies using Power system computer aided design / electromagnetic transients including DC (PSCAD/EMTDC) tool and experimental studies with a laboratory scaled hardware prototype are conducted to confirm the effectiveness of the proposed technique.