Current Differential Protection for Wind Farm Transmission Line Based on Fault Region Fitting Coefficient
Hou Bing1, Li Yifan1, Qin Lansha1, Wang Xuliang1, Li Hui2,3
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2. State Grid Beijing Chaoyang Electric Power Supply Company Beijing 100022 China; 3. Beijing Huairou Laboratory Beijing 101400 China
Abstract：Doubly fed induction generators (DFIGs) are widely used in onshore wind farms. Fault currents in DFIGs are characterized by amplitude limitation and phase angle control, degrading conventional current differential protection based on synchronous power source characteristics. This paper proposes a differential protection scheme using fault region fitting coefficient. It constructs virtual restraint current based on double-end current amplitude coefficients to balance amplitude. An operating boundary model is built using complex domain current vector relationships, determining fault point distribution in the complex plane under internal and external faults. The scheme then constructs the fault boundary in the transient time-domain by deriving trends with transition resistance and restraint coefficient, and adaptively adjusts protection criteria. Firstly, a pilot differential protection scheme based on the fitting coefficient of the fault area is proposed using the transient current information after the fault. To eliminate the differential dead zone problem caused by the weak infeed current on the DFIG side, a virtual restraint current is introduced. Then, based on the differential equation containing the virtual current, a boundary model that can characterize the fluctuation characteristics of the transient current is constructed, and the distribution characteristics of the fault point on the complex plane under both internal and external faults are analyzed through the boundary model. Subsequently, the relationship between the basic parameters of the boundary model and the restraining coefficient, as well as the ratio of the current amplitudes at both ends, is derived using partial differential equations. On this basis, the critical tangential relationship between the transient fault point fitting curve and the boundary circle is utilized to obtain the solving equation for the adaptive fitting coefficient. This equation is used to adjust the restraint level of the differential equation, thereby locking the fault point within the operating region. Finally, the effectiveness of the proposed protection scheme under various fault conditions is verified using a real-time digital simulator (RTDS). The following conclusions can be drawn from the simulation analysis: (1) Compared to traditional models, the proposed protection scheme has low dependence on short-circuit levels. By introducing the ratio of the current amplitudes at both ends to regulate the restraining current, the scheme weakens the differential dead zone problem caused by the weak infeed current on the wind farm side, thereby improving the applicability of the current balance law during internal faults. (2) The proposed model can also simultaneously ensure high-speed operation and reliability. The protection operating equation is adaptively set based on transient electrical information, allowing for fault clearance using only 8 ms of fault current information during the transient time domain. It maintains high reliability even with a 300 Ω transition resistance. (3) The protection setting scheme employs a qualitative rather than quantitative analysis method, providing good adaptability for converter units using mainstream control strategies. Additionally, this method relies solely on current information, eliminating the need for additional voltage transformers, and thus offers high economic efficiency.
侯冰, 李轶凡, 覃岚莎, 汪序亮, 李慧. 基于故障区域拟合系数的双馈风场送出线路纵联差动保护[J]. 电工技术学报, 2025, 40(23): 7694-7706.
Hou Bing, Li Yifan, Qin Lansha, Wang Xuliang, Li Hui. Current Differential Protection for Wind Farm Transmission Line Based on Fault Region Fitting Coefficient. Transactions of China Electrotechnical Society, 2025, 40(23): 7694-7706.
[1] 国家能源局. 国家能源局发布2022年全国电力工业统计数据[J]. 电力勘测设计, 2023(1): I0021. National Energy Administration. National energy administration released statistical data of national electric power industry in2022[J]. Electric Power Survey & Design, 2023(1): I0021. [2] 贾科, 顾晨杰, 毕天姝, 等. 大型光伏电站汇集系统的故障特性及其线路保护[J]. 电工技术学报, 2017, 32(9): 189-198. Jia Ke, Gu Chenjie, Bi Tianshu, et al.Fault characteristics and line protection within the collection system of a large-scale photovoltaic power plant[J]. Transactions of China Electrotechnical Society, 2017, 32(9): 189-198. [3] 闫晨光, 张芃, 徐雅, 等. 换流变压器有载分接开关级间短路故障差动保护动作特性[J]. 电工技术学报, 2023, 38(21): 5878-5888, 5912. Yan Chenguang, Zhang Peng, Xu Ya, et al.Differential protection performance for converter transformer intertap short-circuit faults in on-load tap changers[J]. Transactions of China Electrotechnical Society, 2023, 38(21): 5878-5888, 5912. [4] 肖繁, 夏勇军, 张侃君, 等. 含新能源接入的配电网网络化保护原理研究[J]. 电工技术学报, 2019, 34(增刊2): 709-719. Xiao Fan, Xia Yongjun, Zhang Kanjun, et al.Research on a principle of networked protection in distribution network with renewable energy sources[J]. Transactions of China Electrotechnical Society, 2019, 34(S2): 709-719. [5] 李君, 何敏, 黄守道, 等. 基于相位差的小电阻接地有源配电网接地故障保护算法[J]. 电工技术学报, 2024, 39(23): 7418-7429. Li Jun, He Min, Huang Shoudao, et al.Grounding fault protection algorithm of small resistance earthing active distribution network based on phase difference[J]. Transactions of China Electrotechnical Society, 2024, 39(23): 7418-7429. [6] 李毅, 谢铁兵, 雷阳, 等. 新能源电站非直接接地系统电缆端部单相接地保护方法探讨[J]. 电气技术, 2023, 24(1): 76-80. Li Yi, Xie Tiebing, Lei Yang, et al.Analysis and discussion on the protection method of single-phase grounding at the end of the cable of non-grounded power system[J]. Electrical Engineering, 2023, 24(1): 76-80. [7] 王晨清, 宋国兵, 刘凯, 等. 突变量保护对风电接入系统的适应性分析[J]. 中国电机工程学报, 2014, 34(31): 5485-5492. Wang Chenqing, Song Guobing, Liu Kai, et al.Adaptability analysis of fault component protection of power systems with wind farms[J]. Proceedings of the CSEE, 2014, 34(31): 5485-5492. [8] 王涛, 诸自强, 年珩. 非理想电网下双馈风力发电系统运行技术综述[J]. 电工技术学报, 2020, 35(3): 455-471. Wang Tao, Zhu Ziqiang, Nian Heng.Review of operation technology of doubly-fed induction generator-based wind power system under nonideal grid conditions[J]. Transactions of China Electrotechnical Society, 2020, 35(3): 455-471. [9] 褚旭, 刘琦, 吕昊泽, 等. 基于控保协同海底观测网供电系统保护方案[J]. 电工技术学报, 2023, 38(7): 1780-1792. Chu Xu, Liu Qi, Lü Haoze, et al.Protection scheme for subsea observatory power supply system based on control and protection coordination[J]. Transactions of China Electrotechnical Society, 2023, 38(7): 1780-1792. [10] 束洪春, 刘力滔, 唐玉涛, 等. 基于行波暂态能量的半波长输电线路高灵敏增强型纵联保护方案[J]. 电工技术学报, 2022, 37(24): 6372-6387. Shu Hongchun, Liu Litao, Tang Yutao, et al.Highly sensitive enhanced pilot protection of half-wavelength transmission line based on directional traveling wave energy[J]. Transactions of China Electrotechnical Society, 2022, 37(24): 6372-6387. [11] 马富艺龙, 辛焕海, 刘晨曦, 等. 新能源基地柔性直流送出系统小扰动电压支撑强度评估[J]. 电工技术学报, 2023, 38(21): 5758-5770, 5938. Ma Fuyilong, Xin Huanhai, Liu Chenxi, et al.Small-disturbance system voltage support strength assessment method for renewables VSC-HVDC delivery system[J]. Transactions of China Electrotechnical Society, 2023, 38(21): 5758-5770, 5938. [12] 李彦宾, 贾科, 毕天姝, 等. 电流差动保护在逆变型新能源场站送出线路中的适应性分析[J]. 电力系统自动化, 2017, 41(12): 100-105. Li Yanbin, Jia Ke, Bi Tianshu, et al.Adaptability analysis of current differential protection of outgoing transmission line emanating from inverter-interfaced renewable energy power plants[J]. Automation of Electric Power Systems, 2017, 41(12): 100-105. [13] Zhang Fan, Mu Longhua, Guo Wenming.An integrated wide-area protection scheme for active distribution networks based on fault components principle[J]. IEEE Transactions on Smart Grid, 2019, 10(1): 392-402. [14] 黄方能, 梅勇, 周剑, 等. 基于正序电流的风电接入电网自适应阈值差动保护方案[J]. 电力系统保护与控制, 2022, 50(6): 117-124. Huang Fangneng, Mei Yong, Zhou Jian, et al.Adaptive threshold differential protection scheme for wind power integration based on positive sequence current[J]. Power System Protection and Control, 2022, 50(6): 117-124. [15] 李会新, 王兴国, 谢俊, 等. 一种基于虚拟电流制动量的电流差动保护[J]. 电力系统保护与控制, 2018, 46(9): 75-79. Li Huixin, Wang Xingguo, Xie Jun, et al.A transmission line current differential protection based on virtual brake current[J]. Power System Protection and Control, 2018, 46(9): 75-79. [16] 乔一达, 吴红斌, 吴通华, 等. 含逆变型分布式电源的配电网分区域电流保护[J]. 电工技术学报, 2022, 37(增刊1): 134-144. Qiao Yida, Wu Hongbin, Wu Tonghua, et al.A partitioned current protection scheme of distribution network with inverter interfaced distributed generator[J]. Transactions of China Electrotechnical Society, 2022, 37(S1): 134-144. [17] 黄涛, 陆于平, 蔡超. DFIG等效序突变量阻抗相角特征对故障分量方向元件的影响分析[J]. 中国电机工程学报, 2016, 36(14): 3929-3940. Huang Tao, Lu Yuping, Cai Chao.Analysis of phase angle characteristics of DFIG equivalent sequence superimposed impedances and its impact on fault components based direction relay[J]. Proceedings of the CSEE, 2016, 36(14): 3929-3940. [18] 牛伟民, 樊艳芳, 侯俊杰, 等. 基于正序阻抗幅值比的风电场送出线路纵联保护[J]. 电力系统保护与控制, 2023, 51(16): 179-187. Niu Weimin, Fan Yanfang, Hou Junjie, et al.Pilot protection of wind farm transmission lines based on the positive sequence impedance amplitude ratio[J]. Power System Protection and Control, 2023, 51(16): 179-187. [19] 王春又, 孙士云, 毛肖, 等. 适应于双馈风电场送出线的时域距离纵联方向保护[J]. 电力系统保护与控制, 2021, 49(13): 82-94. Wang Chunyou, Sun Shiyun, Mao Xiao, et al.Longitudinal direction protection of time domain distance applicable to the outgoing line of a double-fed wind farm[J]. Power System Protection and Control, 2021, 49(13): 82-94. [20] Zheng Liming, Jia Ke, Bi Tianshu, et al.A novel structural similarity based pilot protection for renewable power transmission line[J]. IEEE Transactions on Power Delivery, 2020, 35(6): 2672-2681. [21] 胡勇, 郑黎明, 贾科, 等. 基于Tanimoto相似度的光伏场站送出线路纵联保护[J]. 电力系统保护与控制, 2021, 49(3): 74-79. Hu Yong, Zheng Liming, Jia Ke, et al.Pilot protection based on Tanimoto similarity for a photovoltaic station transmission line[J]. Power System Protection and Control, 2021, 49(3): 74-79. [22] Zheng Liming, Jia Ke, Yang Bin, et al.Singular value decomposition based pilot protection for transmission lines with converters on both ends[J]. IEEE Transactions on Power Delivery, 2022, 37(4): 2728-2737. [23] 李铁成, 范辉, 张卫明, 等. 基于5G通信的有源配电网新能源送出线路纵联保护[J]. 中国电力, 2024, 57(11): 139-150. Li Tiecheng, Fan Hui, Zhang Weiming, et al.Pilot protection of new energy transmission line in active distribution network based on 5G communication[J]. Electric Power,, 2024, 57(11): 139-150. [24] Liu Yu, Sakis Meliopoulos A P, Fan Rui, et al. Dynamic State Estimation based protection of microgrid circuits[C]//2015 IEEE Power & Energy Society General Meeting, Denver, CO, USA, 2015: 1-5. [25] 聂铭, 李猛, 和敬涵, 等. 基于状态估计的大规模新能源送出线路纵联保护[J]. 电网技术, 2024, 48(5): 2189-2198. Nie Ming, Li Meng, He Jinghan, et al.Pilot protection of large-scale renewable energy transmission lines based on state estimation[J]. Power System Technology, 2024, 48(5): 2189-2198. [26] 潘学萍, 黄文婷, 郭金鹏, 等. 考虑LVRT特性的新能源送端系统功角稳定与电压稳定交互影响分析[J]. 电力自动化设备, 2024, 44(10): 24-31. Pan Xueping, Huang Wenting, Guo Jinpeng et al. Analysis of interaction between power angle stability and voltage stability for sending-end system with renewable energy considering LVRT characteristics[J]. Electric Power Automation Equipment, 2024, 44(10): 24-31. [27] 徐可寒, 张哲, 刘慧媛, 等. 光伏电源故障特性研究及影响因素分析[J]. 电工技术学报, 2020, 35(2): 359-371. Xu Kehan, Zhang Zhe, Liu Huiyuan, et al.Study on fault characteristics and its related impact factors of photovoltaic generator[J]. Transactions of China Electrotechnical Society, 2020, 35(2): 359-371.
2025, Vol. 40 
