A Novel Protection Strategy for Single Pole-to-Ground Fault in Multi-Terminal DC Distribution Network

Ruixiong Yang, Ke Fang, Jianfu Chen, Yong Chen, Min Liu () and Qingxu Meng
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Ruixiong Yang: DC Power Distribution and Consumption Technology Research Center, Guangdong Power Grid Co., Ltd., Zhuhai 519099, China
Ke Fang: Energy and Electricity Research Center, Jinan University, Zhuhai 519070, China
Jianfu Chen: DC Power Distribution and Consumption Technology Research Center, Guangdong Power Grid Co., Ltd., Zhuhai 519099, China
Yong Chen: DC Power Distribution and Consumption Technology Research Center, Guangdong Power Grid Co., Ltd., Zhuhai 519099, China
Min Liu: Energy and Electricity Research Center, Jinan University, Zhuhai 519070, China
Qingxu Meng: Energy and Electricity Research Center, Jinan University, Zhuhai 519070, China

Energies, 2023, vol. 16, issue 6, 1-16

Abstract: The single pole-to-ground (SPG) fault is one of critical failures which will have a serious impact on the stable operation of the multi-terminal DC distribution network based on the modular multilevel converter (MMC). It is very significant to analyze fault characteristics for detecting faults and protection design. This paper established the DC SPG fault model, which showed that in the presence of a reactor, the short-circuit current was reduced from 2.3 kA to 1 kA at 6 ms after the fault. Then, a novel SPG fault protection strategy was proposed, which detected the current derivative in connection transformer grounding branch. When the value increases past the threshold of current derivative, small resistance was switched on to increase fault current. Thus, the reliability of differential protection was enhanced. Compared with the traditional protection method, the proposed method does not need communication, and improved the speed of protection. Finally, the simulation model was established in PSCAD/EMTDC. The model included three converter stations: T1, T2 and T3. Among them, T1 outputs power, and T2 and T3 receive power. The results of RTDS showed that the DC circuit breaker operated within 3 ms, the three-port circuit breaker worked within 50 ms, which proves that the proposed strategy was effective. At this time, the system switched from the T1–T2–T3 three-terminal networking operation mode to the T1–T2 two-terminal hand-in-hand operation mode. Since the T3 terminal no longer received power, the transmission power of the T1 terminal decreased, and the received power of the T2 terminal remained unchanged.

Keywords: distribution network; single pole-to-ground (SPG) fault; multi-terminal DC; MMC; protection strategy; current derivative (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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