Abstract：With the advantages of reliable system operation, long-distance power transmission, flexible power distribution, etc., the flexible DC power grid is considered a promising solution for efficient renewable energy integration. Flexible DC transmission lines are prone to various faults, and their extremely long length makes the inspection task after faults very tedious. Therefore, fast and accurate fault location technology is necessary to expedite the repair and restoration of the power supply. The single-ended traveling wave fault location method for flexible DC power grids has the advantages of easy implementation and low communication requirements, and is widely used. However, its reliability depends on the accurate identification of the source of the second fault traveling wave, i.e., whether the second traveling wave is from the second reflected wave at the local end or from the first reflected wave at the opposite end. Traditional AC power grids mainly used the traveling wave correlation method and the matched filtering method to identify the source of the second traveling wave. However, due to the distinct traveling wave characteristics of flexible DC power grids during faults compared to AC grids, these methods could not be directly applied to flexible DC power grids. Moreover, these methods only considered short-circuit faults and did not address their applicability to breakage faults. Hence, if the second traveling wave source identification method applicable to flexible DC power grids can be studied that simultaneously accounts for both short-circuit and breakage faults, the fault location reliability of the single-ended traveling wave method can be greatly improved. To this end, this paper explores the second voltage traveling wave characteristics at both ends of the line under DC line short-circuit and breakage faults and proposes a second traveling wave source identification method suitable for flexible DC power grids. The source of the second voltage traveling wave under different faults is first analyzed. It is found that the source of the second voltage traveling wave under unipolar faults may be different, which has to be identified before fault location, while the source of the second voltage traveling wave under bipolar faults is clear, and there is no need to distinguish it in advance. On this basis, the characteristics of the second voltage traveling wave at both ends of the line under unipolar short-circuit fault and unipolar breakage fault are explored, respectively. It is found that the sign of the voltage change rate of the second voltage traveling wave from different sources is different at the moment of its arrival. Based on this property, a method for determining the source of the second traveling wave based on the voltage change rate is proposed. The performance of the proposed method is verified in the PSCAD/EMTDC simulation platform. The results show that the method enables accurate identification of the source of the second traveling wave at both ends of the line under various fault conditions, while exhibiting strong robustness. The conclusions can be drawn as follows: (1) The source of the second voltage traveling wave under a bipolar fault is clear. However, the source of the second voltage traveling wave under a unipolar fault may be different, which has to be identified before fault location. (2) For the unipolar short-circuit fault and unipolar breakage fault, the sign of the voltage change rate of the second voltage traveling wave from different sources is different at the moment of its arrival. Based on this property, a method for determining the source of the second traveling wave based on the voltage change rate is proposed. (3) Extensive simulation experiments verify the effectiveness and robustness of the proposed method.
沈毅, 汤铭萱, 赵振廷, 吴雨晴, 李银红. 基于电压变化率的柔性直流电网第二故障行波来源识别方法[J]. 电工技术学报, 2026, 41(17): 5955-5970.
Shen Yi, Tang Mingxuan, Zhao Zhenting, Wu Yuqing, Li Yinhong. A Method for Identifying the Source of Second Fault Traveling Wave in Flexible DC Power Grid Based on Voltage Change Rate. Transactions of China Electrotechnical Society, 2026, 41(17): 5955-5970.
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2026, Vol. 41 
