Research on Emergency Power Control of AC-DC Hybrid Power System with Flexible DC
Shu Hongchun1,2, Shao Zongxue1,3, Zhao Wei2, Bao Guangjiao2
1. State Key Laboratory of Collaborative Innovation Center for Smart Grid Fault Detection Protection and Control Jointly Kunming University of Science and Technology Kunming 650051 China; 2. Faculty of Electric Power Engineering Kunming University of Science and Technology Kunming 650051 China; 3. Faculty of Mechanical and Electrical Engineering Kunming University of Science and Technology Kunming 650051 China
Abstract:The emergency power control of the DC system is used to balance the power shortage in the system, reduce the frequency deviation of the generator set, and improve the transient frequency stability of the system. In the AC/DC hybrid power system with flexible DC, using the flexible DC to improve the stability of the AC/DC hybrid power system becomes a pressing technical challenge. Traditional DC systems (line commuted converter, LCC) face difficulties in independently controlling active and reactive power during emergency power support, often necessitating the addition of numerous reactive power compensation devices. Therefore, the conventional DC inverter station LCC in the existing AC/DC hybrid system is replaced with a flexible DC converter station (voltage source converter, VSC). Based on the respective advantages of LCC-LCC and LCC-VSC, a prioritized coordination control strategy for emergency power support is proposed. When the AC/DC hybrid system with flexible DC needs DC emergency power support, the LCC-VSC is preferentially used to provide emergency power support to the system. If the power shortage exceeds the power regulation margin of LCC-VSC, the remaining power is transmitted by LCC-LCC. The fast power regulation characteristics of the DC system are used to rebalance the system power shortage. Firstly, the theory of DC participation in emergency frequency support is analyzed. Then, a priority hierarchical coordinated control strategy is designed. Finally, simulation results verify the effectiveness of the proposed scheme in realizing emergency frequency support. For the AC system N-1, N-2 fault, and LCC bipolar blocking three fault conditions in the AC/DC hybrid power system with flexible DC, the flexible DC is preferentially selected for emergency power support control. When an N-1 fault occurs, compared to situations without DC emergency power support, LCC-VSC is preferred for emergency power support. The transmission power burden of non-fault pole AC line 2 is greatly alleviated, the AC frequency fluctuation rate is reduced by 40%, and the system frequency is quickly restored and stabilized to 50 Hz. When an N-2 fault occurs, the system frequency offset exceeds 0.5 Hz without DC emergency power support. However, using the LCC-VSC as the primary emergency power support and LCC-LCC for additional support, the system frequency fluctuation rate is reduced by 65.9%, and the LCC-LCC and LCC-VSC transmission power values are within the allowable range. When LCC-LCC bipolar blocking, LCC-LCC VSC is preferred for emergency power support, and the remaining power is transmitted by AC lines 1 and 2. The system frequency fluctuation rate is reduced by 20%. Through the emergency power coordinated control of LCC-VSC and LCC-LCC, the system frequency is quickly restored to stability. After the emergency power coordinated control starts, the system frequency is basically restored to 50 Hz after 60 ms. When relying solely on LCC-LCC for emergency power control, the system frequency recovery time is significantly longer than the coordinated control of LCC-VSC and LCC-LCC.
束洪春, 邵宗学, 赵伟, 包广皎. 含柔性直流的交直流混联电力系统紧急频率控制研究[J]. 电工技术学报, 2023, 38(20): 5590-5604.
Shu Hongchun, Shao Zongxue, Zhao Wei, Bao Guangjiao. Research on Emergency Power Control of AC-DC Hybrid Power System with Flexible DC. Transactions of China Electrotechnical Society, 2023, 38(20): 5590-5604.
[1] 辛保安, 郭铭群, 王绍武, 等. 适应大规模新能源友好送出的直流输电技术与工程实践[J]. 电力系统自动化, 2021, 45(22): 1-8. Xin Baoan, Guo Mingqun, Wang Shaowu, et al.Friendly HVDC transmission technologies for largescale renewable energy and their engineering practice[J]. Automation of Electric Power Systems, 2021, 45(22): 1-8. [2] 丁剑, 方晓松, 宋云亭, 等. 碳中和背景下西部新能源传输的电氢综合能源网构想[J]. 电力系统自动化, 2021, 45(24): 1-9. Ding Jian, Fang Xiaosong, Song Yunting, et al.Conception of electricity and hydrogen integrated energy network for renewable energy transmission in Western China under background of carbon neutralization[J]. Automation of Electric Power Systems, 2021, 45(24): 1-9. [3] 梁紫雯, 牟龙华, 何楚璇. 微能源网互联系统的频率调节和消纳能力研究[J]. 电工技术学报, 2022, 37(增刊1): 74-82 Liang Ziwen, Mu Longhua, He Chuxuan.Research on frequency modulation and accommodation capability of interconnected system of micro-energy network[J]. Transactions of China Electrotechnical Society, 2022, 37(S1): 74-82 [4] 李兆伟, 方勇杰, 黄慧, 等. 系统保护中跨区直流频率调制与紧急功率支援的协调控制[J]. 电力系统自动化, 2020, 44(22): 31-36. Li Zhaowei, Fang Yongjie, Huang Hui, et al.Coor- dinated control of cross-region DC frequency control and emergency power support in system protection[J]. Automation of Electric Power Systems, 2020, 44(22): 31-36. [5] 柯德平, 冯帅帅, 刘福锁, 等. 新能源发电调控参与的送端电网直流闭锁紧急频率控制策略快速优化[J]. 电工技术学报, 2022, 37(5): 1204-1218. Ke Deping, Feng Shuaishuai, Liu Fusuo, et al.Rapid optimization for emergent frequency control strategy with the power regulation of renewable energy during the loss of DC connection[J]. Transactions of China Electrotechnical Society, 2022, 37(5): 1204-1218. [6] 李兆伟, 方勇杰, 黄慧, 等. 系统保护中跨区直流频率调制与紧急功率支援的协调控制[J]. 电力系统自动化, 2020, 44(22): 31-36. Li Zhaowei, Fang Yongjie, Huang Hui, et al.Coordinated control of cross-region DC frequency control and emergency power support in system protection[J]. Automation of Electric Power Systems, 2020, 44(22): 31-36. [7] Renedo J, García-Cerrada A, Rouco L.Reactive- power coordination in VSC-HVDC multi-terminal systems for transient stability improvement[J]. IEEE Transactions on Power Systems, 2017, 32(5): 3758-3767. [8] Li Congshan, He Ping, Wang Youyi, et al.HVDC auxiliary emergency power control strategy for power disturbance in two different positions of AC/DC interconnection system[J]. Archives of Electrical Engineering, 2023, 68(2): 1427-4221. [9] Li Hucheng, Yuan Yubo, Zhang Xiaoyi, et al.Analysis of frequency emergency control characte- ristics of UHV AC/DC large receiving end power grid[J]. The Journal of Engineering, 2017, 36(2): 2096-3203. [10] Wen Yunfeng, Chung C Y, Ye Xi.Enhancing frequency stability of asynchronous grids inter- connected with HVDC links[J]. IEEE Transactions on Power Systems, 2018, 33(2): 1800-1810. [11] 朱玲, 王晓茹, 卢岑岑, 等. 基于BPA的大电网紧急直流功率支援策略研究[J]. 电力系统保护与控制, 2013, 41(23): 139-144. Zhu Ling, Wang Xiaoru, Lu Cencen, et al.Research of emergency DC power support strategies for large-scale power grid based on PSD-BPA[J]. Power System Protection and Control, 2013, 41(23): 139-144. [12] Shi Zheng, Xu Yin, Wu Xiangyu, et al.Coordinated emergency control strategy for transient stability enhancement of AC/DC hybrid power systems based on EEAC theory[C]//2018 IEEE 2nd International Electrical and Energy Conference (CIEEC), Beijing, China, 2019: 88-93. [13] 胡益, 王晓茹. 一种计及紧急功率支援的直流互联异步电网动态频率分析方法[J]. 电网技术, 2018, 42(9): 2859-2878. Hu Yi, Wang Xiaoru.Dynamic frequency analysis method of DC interconnected asynchronous power grid considering emergency power support[J]. Power System Technology, 2018, 42(9): 2859-2878. [14] Rahimi E, Gole A M, Davies J B, et al.Commutation failure analysis in multi-infeed HVDC systems[J]. IEEE Transactions on Power Delivery, 2011, 26(1): 378-384. [15] 王莹, 刘兵, 刘天斌, 等. 特高压直流闭锁后省间紧急功率支援的协调优化调度策略[J]. 中国电机工程学报, 2015, 35(11): 2695-2702. Wang Ying, Liu Bing, Liu Tianbin, et al.Coordinated optimal dispatching strategy of emergency power support between provinces after UHVDC lockout[J]. Proceedings of the CSEE, 2015, 35(11): 2695-2702. [16] 王建明, 孙华东, 张健, 等. 锦屏—苏南特高压直流投运后电网的稳定特性及协调控制策略[J]. 电网技术, 2012, 36(12): 66-70. Wang Jianming, Sun Huadong, Zhang Jian, et al.Stability characteristics and coordinated control strategy of interconnected grid integrated with UHVDC transmission line from Jinping to Sunan[J]. Power System Technology, 2012, 36(12): 66-70. [17] 余涛, 沈善德, 任震. 华中-华东多回HVDC紧急功率转移控制的研究[J]. 电网技术, 2004, 28(12): 1-4. Yu Tao, Shen Shande, Ren Zhen.Research on emergency power shifting control of multi-circuit HVDC systems from central China power grid to East China power grid[J]. Power System Technology, 2004, 28(12): 1-4. [18] 陈睿, 孙仲卿, 杨银国, 等. 柔性直流与常规直流协调的紧急功率支援策略研究[J]. 电力工程技术, 2017, 36(6): 14-19. Chen Rui, Sun Zhongqing, Yang Yinguo, et al.Emergency power support control strategy of VSC- HVDC and LCC-HVDC coordination[J]. Jiangsu Electrical Engineering, 2017, 36(6): 14-19. [19] 李从善, 和萍, 金楠, 等. 基于不平衡功率动态估计的直流幅值阶梯递增紧急功率支援[J]. 电力自动化设备, 2018, 38(12): 148-154. Li Congshan, He Ping, Jin Nan, et al.DC amplitude stepped incremental emergency power support based on dynamic estimation of unbalanced power[J]. Electric Power Automation Equipment, 2018, 38(12): 148-154. [20] 朱红萍, 罗隆福. 直流调制策略改善交直流混联系统的频率稳定性研究[J]. 中国电机工程学报, 2012, 32(16): 36-43. Zhu Hongping, Luo Longfu.Improving frequency stability of parallel AC-DC hybrid systems by power modulation strategy of HVDC link[J]. Proceedings of the CSEE, 2012, 32(16): 36-43. [21] Koch H, Vögele S, Hattermann F F, et al.The impact of climate change and variability on the generation of electrical power[J]. Meteorologische Zeitschrift, 2015, 24(2): 173-188. [22] 陈厚合, 王长江, 姜涛, 等. 基于端口能量的含VSC-HVDC的交直流混合系统暂态稳定评估[J]. 电工技术学报, 2018, 33(3): 498-511. Chen Houhe, Wang Changjiang, Jiang Tao, et al.Transient stability assessment in hybrid AC/DC systems with VSC-HVDC via port energy[J]. Transa- ctions of China Electrotechnical Society, 2018, 33(3): 498-511. [23] 李国庆, 孙银锋, 吴学光. 柔性直流输电稳定性分析及控制参数整定[J]. 电工技术学报, 2017, 32(6): 231-239. Li Guoqing, Sun Yinfeng, Wu Xueguang.VSC- HVDC stability analysis and control parameter setting[J]. Transactions of China Electrotechnical Society, 2017, 32(6): 231-239. [24] 李忆恺. 混合多馈入直流输电系统紧急功率支援控制及阻尼低频振荡研究[D]. 郑州: 郑州轻工业大学, 2020. [25] 卞志鹏. 提升电力系统安全稳定性的VSC分析与控制策略研究[D]. 杭州: 浙江大学, 2019. [26] 许涛, 吴雪莲, 李兆伟, 等. 改善系统频率稳定性的多直流功率紧急支援协调控制策略[J]. 电力系统自动化, 2018, 42(22): 69-77. Xu Tao, Wu Xuelian, Li Zhaowei, et al.Coordinated control strategy of multi-DC emergency power support to improve frequency stability of power systems[J]. Automation of Electric Power Systems, 2018, 42(22): 69-77.