CJEE

Chinese Journal of Electrical Engineering ›› 2021, Vol. 7 ›› Issue (2): 83-92.doi: 10.23919/CJEE.2021.000018

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Fast Protection Strategy for DC Transmission Lines of MMC-based MT-HVDC Grid*

Sihua Wang1,2, Lijun Zhou1,2,*, Tian Wang1,2, Tianyu Chen1,2, Yu Wang1,2   

  1. 1. College of Automation & Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China;
    2. Rail Transit Electrical Automation Engineering Laboratory of Gansu Province, Lanzhou Jiaotong University, Lanzhou 730070, China
  • Received:2020-01-08 Revised:2020-06-30 Accepted:2020-08-06 Online:2021-06-25 Published:2021-07-08
  • Contact: * E-mail: lijunzhou93@163.com
  • About author:Sihua Wang was born in Jiangsu Province, China, on May 21, 1968. He graduated from the East China Jiaotong University, electrical engineering and automation in Jiangxi, China, in 1995.
    He is a professor at Lanzhou Jiaotong University, Lanzhou, China. His research interests concern reliability of substation integrated automation and direction of HV insulation.
    Lijun Zhou was born in Gansu Province, China, on August 3, 1996. She is studying for a master's degree in power system and automation at Lanzhou Jiaotong University, Lanzhou, China. Her research interests concern protection and control of HVDC power grid.
    Tian Wang was born in Gansu, China, on September 25, 1995. She is studying for a master's degree in electrical engineering at Lanzhou Jiaotong University, Lanzhou, China. Her research interests concern fault monitoring and diagnosis of new energy grid.
    Tianyu Chen was born in Zhejiang, China, on October 9, 1995. He is studying for a master's degree in electrical engineering at Lanzhou Jiaotong University, Lanzhou, China. His research interests concern monitoring and control of electrified railway.
    Yu Wang was born in Hubei, China, on April 3, 1994. He is studying for a master's degree in electrical engineering at Lanzhou Jiaotong University, Lanzhou, China. His research interests concern overvoltage and lightning protection grounding technology.
  • Supported by:
    * National Natural Science Foundation of China (51767014) and the Scientific and Technological Research and Development Program of the China Railway (2017J010-C/2017).

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Abstract: ：Multi-terminal high voltage DC (MT-HVDC) grid has broad application prospects in connecting different energy sources, asynchronous interconnection of power grids, remote load power supply, and other fields. At present, the key technologies that affect the development of MT-HVDC transmission system include swift fault identification and location in the DC line and its rapid isolation. Traditional fault monitoring relies on line communication, which cannot guarantee the rapidity and reliability of protection; moreover, it may even cause device damage. A fault identification scheme based on a single-terminal transient is presented in this paper. This scheme calculates the line inductance by using the rise rate of fault current at the initial stage of the fault, and determines the occurrence of the fault by comparing the observed line inductance with the set value, which lays a foundation for calculating the location of the fault point using distance protection. A simulation model on the PSCAD/EMTDC platform is built; the simulation example verifies that the proposed scheme can identify faults under dissimilar conditions while maintaining a low error level on the premise of no communication lines so as to meet the protection requirements of the MT-HVDC grid.

Key words: Multi-terminal high voltage DC (MT-HVDC) grid, modular multilevel converter (MMC), DC circuit breaker (DCCB), bipolar short-circuit, fault identification