Non-Injection Single-Ended Time-Domain Distance Protection for Renewable Energy Transmission System via Islanded Flexible DC
Zhang Ruozhu1, Zheng Tao1, Lü Wenxuan2, Liu Sen1
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2. State Grid Jiangsu Electric Power Co. Ltd Electric Power Science Research Institute Nanjing 211100 China
Abstract：In renewable energy transmission system via islanded flexible DC, both ends of the 220 kV AC transmission lines feature controllable power electronic devices. The short-circuit currents of both ends of the line contain significant harmonic components, which makes it difficult to apply the traditional distance protection. Time-domain distance protection has garnered significant attention due to its immunity to harmonic effects. However, phase differences between currents at both ends of the line, influenced by factors such as line distribution capacitance and feed-in current from the opposite side, compromise the accuracy of traditional time-domain distance protection calculations. Existing improved time-domain distance protection schemes typically employ injection methods. By actively modulating a specific frequency component through the MMC converter, the opposite side system is equivalent to an open circuit, equating double-ended supply systems to single-ended systems to mitigate the impact of current injection from the opposite end. Nevertheless, the implementation of injection-based protection schemes is often constrained by practical engineering limitations. In light of this, this paper proposes a non-injection single-ended time-distance protection for renewable energy transmission system via islanded flexible DC. Firstly, taking into account the influence of the line distribution capacitance, the line π-equivalent model is used to equivalent fault circuit. Secondly, based on the phase lag or lead relationship between the MMC converter-side current and fault current, equivalent resistance-inductance or resistance-capacitance are introduced to replace the original fault resistance. This accounts for the influence of phase differences between the two sides. Time-domain differential equations are subsequently derived for both phase-to-ground faults and phase-to-phase faults under equivalent resistance-inductance or resistance-capacitance conditions respectively. The intrinsic relationship between these two scenarios is then analyzed, unifying the time-domain differential equation expressions. Subsequently, the fault distance is solved by using the least-squares algorithm, and the protection criterion is constructed. Finally, the feasibility and effectiveness of the proposed scheme are verified by PSCAD/EMTDC simulation platform. Simulation results show that the proposed time-domain distance protection scheme can be adapted to both phase-to-ground faults and phase-to-phase faults, and has good ability to identify fault resistance. The time-domain distance protection scheme proposed in this paper has good anti-interference performance. Using the time-domain distance protection scheme proposed in this paper to calculate the fault distance can reach stability within 10ms after the fault, and the relative error of the calculated fault distance is less than 4%. The following conclusions can be drawn: (1) The introduction of the equivalent resistance-inductance or resistance-capacitance instead of the original fault resistance eliminates the influence of the phase difference between the short-circuit current of MMC converter and the current at the fault point on the performance of the time-domain distance protection, and significantly improves the reliability of the time-domain distance protection. (2) By analyzing the intrinsic relationship between the time-domain differential equations represented by equivalent resistance-inductance or resistance-capacitance, the expressions for the time-domain differential equations in both scenarios have been unified. The unified time-domain differential equations can be applied to different fault scenarios. (3) The calculated fault distance according to the proposed time-domain distance protection has a high accuracy, which can be stabilized within 10ms after the fault. The proposed scheme has a good ability to identify fault resistance, and is adaptable to different fault scenarios with good universality.
章若竹, 郑涛, 吕文轩, 刘森. 适用于新能源经柔直孤岛送出的非注入式单端时域距离保护[J]. 电工技术学报, 2026, 41(18): 6381-6395.
Zhang Ruozhu, Zheng Tao, Lü Wenxuan, Liu Sen. Non-Injection Single-Ended Time-Domain Distance Protection for Renewable Energy Transmission System via Islanded Flexible DC. Transactions of China Electrotechnical Society, 2026, 41(18): 6381-6395.
[1] 文明浩, 陈玉, 王玉玺, 等. 基于正序d轴电流变化量的逆变型电源场站送出线保护方向元件[J]. 电力系统自动化, 2025, 49(14): 190-199. Wen Minghao, Chen Yu, Wang Yuxi, et al.Protection directional element for transmission line of inverter-interfaced generator station based on positive-sequence d-axis current variation[J]. Automation of Electric Power Systems, 2025, 49(14): 190-199. [2] 郑涛, 刘昱彤, 章若竹, 等. 计及双二阶锁相环动态过程影响的锁相偏差检测及相位补偿[J]. 电工技术学报, 2025, 40(15): 4818-4834. Zheng Tao, Liu Yutong, Zhang Ruozhu, et al.Phase-locked deviation detection and phase angle compen-sation scheme considering the influence of dynamic process of DSOGI-PLL[J]. Transactions of China Electrotechnical Society, 2025, 40(15): 4818-4834. [3] 马燕峰, 韩珊珊, 王子建, 等. 直驱风电场经柔直外送系统振荡特性及控制环节动态交互作用研究[J/OL]. 电工技术学报, 2025: 1-17. (2025-05-12). https://link.cnki.net/doi/10.19595/j.cnki.1000-6753.tces.250460. Ma Yanfeng, Han Shanshan, Wang Zijian, et al. Study on oscillation characteristics and dynamic interaction of control link of a VSC-HVDC connected direct drive wind farm[J/OL]. Transactions of China Electro-technical Society, 2025: 1-17. (2025-05-12). https://link.cnki.net/doi/10.19595/j.cnki.1000-6753.tces.250460. [4] 温志文, 贾科, 余磊, 等. 基于时频特性相似度的新能源场站T接型送出线路高速保护[J]. 电力系统保护与控制, 2023, 51(4): 1-11. Wen Zhiwen, Jia Ke, Yu Lei, et al.High speed protection based on time-frequency characteristic similarity for a Teed transmission line connected to renewable energy power plants[J]. Power System Protection and Control, 2023, 51(4): 1-11. [5] Zhong Xian, Fan Yanfang, Chen Weiwei, et al.Study on LVRT coordinate control strategy of DFIG when considering non-rotor side crowbar protection[J]. Journal of Computational Information Systems, 2015, 11(18): 6747-6757. [6] Yan Kai, Zhang Baohui, Hao Zhiguo.Analysis and improvement of relay protection for photovoltaic power station connected to power grid[C]//2013 The Fourteenth National Symposium on Protection and Control, Zhengzhou, 2013: 1-7. [7] 翟学, 林涛, 吴俊鹏, 等. 含光伏电站的电网自适应接地距离保护研究[J]. 中国电力, 2016, 49(2): 78-83. Zhai Xue, Lin Tao, Wu Junpeng, et al.Research on adaptive grounding distance protection in grid with photovoltaic power plant[J]. Electric Power, 2016, 49(2): 78-83. [8] 索南加乐, 齐军, 陈福锋, 等. 基于R-L模型参数辨识的输电线路准确故障测距算法[J]. 中国电机工程学报, 2004, 24(12): 119-125. Suo Nanjiale, Qi Jun, Chen Fufeng, et al.An accurate fault location algorithm for transmission lines based on R-L model parameter identification[J]. Proceedings of the CSEE, 2004, 24(12): 119-125. [9] 龚永智, 陶晔, 许传敏, 等. 考虑风电机组馈入电流的风电场汇集线路保护整定计算方法[J]. 电力系统保护与控制, 2020, 48(11): 128-135. Gong Yongzhi, Tao Ye, Xu Chuanmin, et al.Relay protection setting calculation of wind farm collector lines considering wind turbine increased short-circuit current[J]. Power System Protection and Control, 2020, 48(11): 128-135. [10] 索南加乐, 刘文涛, 陈勇, 等. 基于R-L模型误差的自适应距离保护[J]. 电力系统自动化, 2006, 30(22): 66-72. Suo Nanjiale, Liu Wentao, Chen Yong, et al.Adaptive distance protection based on R-L model error[J]. Automation of Electric Power Systems, 2006, 30(22): 66-72. [11] 陈学伟, 高厚磊, 向珉江, 等. 基于电子式互感器微分输出的改进R-L模型距离保护算法[J]. 电工技术学报, 2014, 29(6): 283-289. Chen Xuewei, Gao Houlei, Xiang Minjiang, et al.Improved R-L model distance protection algorithm based on differential output of electronic transducers[J]. Transactions of China Electrotechnical Society, 2014, 29(6): 283-289. [12] 罗瑞, 樊艳芳, 刘群杰. 基于时域的交直流混联系统抗过渡电阻的单相接地距离保护研究[J]. 电力系统及其自动化学报, 2019, 31(12): 123-129. Luo Rui, Fan Yanfang, Liu Qunjie.Research on anti-transition resistance single-phase ground distance protection of AC-DC hybrid power system based on time-domain[J]. Proceedings of the CSU-EPSA, 2019, 31(12): 123-129. [13] 裘愉涛, 潘武略, 倪传坤, 等. 风电场送出线等传变距离保护[J]. 电力系统保护与控制, 2015, 43(12): 61-66. Qiu Yutao, Pan Wulüe, Ni Chuankun, et al.Equal transfer process-based distance protection for wind farm outgoing transmission line[J]. Power System Protection and Control, 2015, 43(12): 61-66. [14] 范小红, 孙士云, 张雪娟, 等. 双馈风电场短路电流特性对距离保护的影响及保护策略研究[J]. 电力系统保护与控制, 2020, 48(11): 18-27. Fan Xiaohong, Sun Shiyun, Zhang Xuejuan, et al.Study on the influence of short-circuit current characteristics of a doubly-fed wind farm on distance protection and protection strategy[J]. Power System Protection and Control, 2020, 48(11): 18-27. [15] 宋国兵, 侯俊杰, 郭冰. 基于主动探测式的混合MMC直流输电系统单端量故障定位[J]. 电网技术, 2021, 45(2): 730-740. Song Guobing, Hou Junjie, Guo Bing.Single-ended fault location of hybrid MMC-HVDC system based on active detection[J]. Power System Technology, 2021, 45(2): 730-740. [16] 宋国兵, 王婷, 张保会, 等. 利用电力电子装置的探测式故障识别技术分析与展望[J]. 电力系统自动化, 2020, 44(20): 173-183. Song Guobing, Wang Ting, Zhang Baohui, et al.Analysis and prospect of detective fault identification technologies using power electronic device[J]. Automation of Electric Power Systems, 2020, 44(20): 173-183. [17] 郑涛, 章若竹, 吕文轩, 等. 基于故障主动控制的海上风电交流汇集线路时域距离保护[J]. 电工技术学报, 2025, 40(1): 122-138. Zheng Tao, Zhang Ruozhu, Lü Wenxuan, et al.Time-domain distance protection of offshore AC transmission lines based on fault active control considering distributed capacitance’s impact[J]. Transactions of China Electrotechnical Society, 2025, 40(1): 122-138. [18] Zheng Tao, Zhang Ruozhu, Lü Wenxuan, et al.Improved time-domain distance protection based on fault active control for long transmission lines of PV/ BES hybrid power generation system[J]. International Journal of Electrical Power & Energy Systems, 2024, 159: 110049. [19] 徐瑞东, 常仲学, 宋国兵, 等. 注入探测信号的直流配电网接地故障识别方法[J]. 电网技术, 2021, 45(11): 4269-4277. Xu Ruidong, Chang Zhongxue, Song Guobing, et al.Grounding fault identification method for DC distribution network based on detection signal injection[J]. Power System Technology, 2021, 45(11): 4269-4277. [20] 侯俊杰, 樊艳芳. 基于分布参数模型的风电系统长距离送出线时域距离保护[J]. 电力系统保护与控制, 2018, 46(19): 26-33. Hou Junjie, Fan Yanfang.Time domain distance protection for long distance outgoing line of wind power system based on distributed parameter model[J]. Power System Protection and Control, 2018, 46(19): 26-33. [21] 侯俊杰, 宋国兵, 常鹏, 等. 计及对端系统参数和送出线路分布参数影响的风电系统时域距离保护[J]. 电力系统保护与控制, 2022, 50(5): 106-116. Hou Junjie, Song Guobing, Chang Peng, et al.Time-domain distance protection for a wind power system considering parameters of the remote end system and influence of outgoing line distribution parameters[J]. Power System Protection and Control, 2022, 50(5): 106-116. [22] 罗强. 过渡电阻对柔直近端交流线路距离保护的影响研究[D]. 武汉: 华中科技大学, 2019. Luo Qiang.Impact of transition resistance on distance protection of the AC transmission line near the MMC-HVDC system[D]. Wuhan: Huazhong University of Science and Technology, 2019. [23] 索南加乐, 王增超, 张健康, 等. 基于参数识别的高阻接地距离保护算法[J]. 中国电机工程学报, 2011, 31(31): 173-178. Suo Nanjiale, Wang Zengchao, Zhang Jiankang, et al.A novel distance protection algorithm for high resistance grounding faults based on parameter identification[J]. Proceedings of the CSEE, 2011, 31(31): 173-178. [24] 范兴明, 封浩, 张鑫. 最小二乘算法优化及其在锂离子电池参数辨识中的应用[J]. 电工技术学报, 2024, 39(5): 1577-1588. Fan Xingming, Feng Hao, Zhang Xin.Optimization of least squares method and its application in parameter identification of lithium-ion battery model[J]. Transactions of China Electrotechnical Society, 2024, 39(5): 1577-1588. [25] 田艳军, 宋少鹏, 徐小奇, 等. 基于卡尔曼滤波数据优化与非线性最小二乘法的IGBT饱和压降监测技术[J/OL]. 电工技术学报, 2025: 1-17. (2025-06-30). https://link.cnki.net/doi/10.19595/j.cnki.1000-6753.tces.250675. Tian Yanjun, Song Shaopeng, Xu Xiaoqi, et al. IGBT saturation voltage drop monitoring technology based on Kalman filter data optimization and nonlinear least squares method[J/OL]. Transactions of China Electro-technical Society, 2025: 1-17. (2025-06-30). https://link.cnki.net/doi/10.19595/j.cnki.1000-6753.tces.250675.
2026, Vol. 41 
