基于相空间暂态映射轨迹的复杂多端柔直配电网单极接地保护

doi:10.19595/j.cnki.1000-6753.tces.260051

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摘要

针对复杂多端柔直配电网接地故障特征微弱、现有保护方法依赖边界元件或对过渡电阻与噪声敏感问题,提出一种基于相空间暂态映射轨迹的单极接地保护方法。首先,系统分析不同换流器接地方式及虚拟开断点位置对故障暂态特性的影响机理,揭示区内、外故障暂态电流时域特征;其次,将时域信号映射至二维相空间,利用其几何形态特征构造基于初始象限分布与主轴偏移度的双重化辨识判据。基于PSCAD/EMTDC的仿真结果表明,所提方法无需依赖边界元件,可耐受200Ω高过渡电阻,受噪声干扰较小,可以实现复杂多端柔直配电网弱特征故障的可靠辨识。

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关键词 ：柔性直流配电网, 单极接地故障, 相空间重构, 主轴偏移度, 弱特征故障

Abstract：

Driven by the strategic goals of "carbon peaking and carbon neutrality," the growing integration of diversified DC loads is accelerating the evolution of distribution networks toward flexible DC systems. Flexible DC distribution, characterized by large transmission capacity and flexible power flow control, has emerged as a key technological pathway for building new-type power systems. However, fault transient characteristics are deeply coupled with converter control strategies, resulting in an extremely short available data window, and multi-terminal complex network topologies significantly increase the difficulty of fault identification. Existing protection schemes face three major challenges: (1) Excessive dependence on boundary components, such as current-limiting reactors, limits the applicability of existing protection schemes in multi-terminal meshed structures where boundaries are weak or absent; (2) Conventional directional criteria are disturbed by transient oscillations and nonlinear waveform distortions, degrading the performance of waveform correlation-based identification methods; (3) In neutral ineffectively grounded systems, the single-pole-to-ground fault current is inherently weak, exhibiting strong nonlinearity and non-monotonic characteristics, which makes fault identification extremely difficult.
To address these challenges, this paper first conducts an in-depth analysis of the single-pole-to-ground fault mechanism in complex multi-terminal flexible DC distribution networks. Considering the different grounding configurations of multiple converter types—including MMC, VSC, and DCT—and based on the "virtual breaking point" theory, the short-circuit current expressions under different fault scenarios are systematically derived, and the transient characteristic differences between internal and external faults are clearly identified. Subsequently, breaking through the limitations of traditional time-domain analysis, the fault current signal is mapped into a two-dimensional phase space. The single RLC-dominant response exhibits regular concentric shrinking ellipses due to time-delay orthogonality, while the multi RLC-superimposed response presents chaotic trajectories due to the destruction of orthogonality. Based on these significant geometric morphological differences, dual criteria of "initial quadrant distribution" and "principal axis offset" are constructed, and a single-pole-to-ground protection method based on phase-space transient mapping trajectory is proposed. Finally, simulation validation is conducted in PSCAD/EMTDC on a 10 kV six-terminal flexible DC distribution network model.
The conclusions can be drawn as follows: (1) Considering the virtual breaking point location and grounding configurations of multiple converter types, the time-domain transient signals of internal and external faults may exhibit similar characteristics in both amplitude and direction under different scenarios. For internal faults with the virtual breaking point K located on the fault line and external faults with K located on other lines, the currents on both sides are in opposite directions. For internal faults with K located on a non-fault line and external faults with K located on other lines, both exhibit multi-RLC superposition characteristics. (2) In the high-dimensional phase space, the single RLC-dominant response exhibits regular concentric shrinking ellipses due to time-delay orthogonality, while the multi RLC-superimposed response presents chaotic trajectories. By characterizing the phase-space trajectory features with initial quadrant distribution and principal axis offset, dual criteria are constructed to achieve reliable fault identification. (3) The proposed method does not rely on boundary components, is less affected by noise, does not require strict signal synchronization, and can withstand transition resistance up to 200 Ω.

Key words： Flexible DC distribution network single-pole-to-ground fault phase space reconstruction principal axis deviation weak-characteristic fault

收稿日期: 2026-01-11

PACS:

TM77

基金资助:

国家自然科学基金资助项目（52577108）

通讯作者: 戴志辉男,1980年生,教授,博士生导师,研究方向为电力系统保护与控制。E-mail: daihuadian@163.com

作者简介: 李涵伟男,2002年生,硕士研究生,研究方向为电力系统保护与控制。E-mail: lihamwei@163.com

引用本文:

戴志辉, 李涵伟, 史琛, 惠天翼. 基于相空间暂态映射轨迹的复杂多端柔直配电网单极接地保护[J]. 电工技术学报, 0, (): 260051-. Dai Zhihui, Li Hanwei, Shi Chen, Hui Tianyi. Single-Pole Ground Fault Protection for Complex Multi-Terminal Flexible DC Distribution Networks Based on Phase Space Transient Mapping Trajectory. Transactions of China Electrotechnical Society, 0, (): 260051-.

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