Proactive Scheduling of Resilient Distribution Systems Considering Power Impact During Islanded Microgrid Formation Process
Cai Sheng1, Xie Yunyun1, Zhang Yuping1, Guo Jian1, Chen Xiong2
1. School of Automation Nanjing University of Science and Technology Nanjing 210094 China; 2. NARI Group Corporation State Grid Electric Power Research Institute Nanjing 210094 China
Abstract：When an emergency accident occurs in the distribution system under extreme conditions, multiple islanded microgrids (IMGs) are formed to ensure constant power supply to critical loads, which is essential for reducing outage range and enhancing system resilience. However, traditional IMG formation methods focuses on passive MG formation after an emergency and, hence, cannot guarantee the successful IMG formation in the event of significant power imbalance. Recently, proactive approaches were presented to ensure adequate spinning reserve in supplying load demand after the IMG formation, but most of them ignored the non-zero power flow at the moment line disconnects. This was insufficient to ensure a successful MG formation because the significant power impact may lead to the frequency instability in IMGs. To address these issues, this paper proposed a proactive scheduling method that considers the power impact during the IMG formation process. By mitigating the power impact when line outage happens, IMGs can be formed safely and reliably after extreme event happens. Firstly, a pre- and post-disaster two-stage coordinated stochastic model that considers the power impact was formulated to minimize the operation costs and load shedding. Next, the nonlinear terms in original model were linearized, and thus the nonlinear stochastic model was transformed to a mixed integer linear programming problem to facilitate solution. The main differences between the proposed proactive scheduling model and those in existing literature lie in the line transmission power constraints, in which decision variables $W_{i j}^{\mathrm{p}}$ and $W_{i j}^{\mathrm{q}}$ were introduced to restrict the power flow on vulnerable lines prior to the extreme event. In addition, unit commitment and network reconfiguration were also considered in the proposed model to enhance the flexibility of scheduling scheme. Simulation results on the modified IEEE 13 bus distribution system show that, prior to the event strikes, switches on lines 671-692 and 684-611 are opened and switches on lines 633-692 and 646-611 are closed to optimize the configuration of distribution network. To satisfy the power impact constraint during IMG formation, power flow on lines is restricted and appropriate load shedding (600 kW in this case) is allowed at the pre-disaster stage. When line outage emergencies occur, several IMG are seamless formed to continue supporting critical loads. The total generation of power sources in one MG is equal to the total amount of load consumption for each time step. Comparison of different operation methods shows that, the successful IMG formation rate for operation method with/without considering proactive scheduling is 83.3% and 26.7%, respectively. In other words, the proposed method can improve IMGs’ survivability after disaster but understandably cannot totally avoid the collapse. This is because the stochastic approach cannot be able to cover all the contingency scenarios that may occur. The comparison with proactive scheduling method without network reconfiguration shows that, the optimal network topology can reduce the amount of load shedding by forming more flexible IMGs and improve energy utilization efficiency of power sources. The comparison with traditional preventive defensive islanding method shows that, the proposed method can reduce the amount of load shedding by about 15%. This is because the proposed method reduces power imbalance in MGs through restricting power flow on vulnerable lines rather than totally avoid it. Therefore, less conservative proactive scheduling schemes resulting in less load shedding can be obtained. The following conclusions can be drawn from the simulation analysis: (1) Compared with traditional distribution system scheduling method, proactive scheduling can reduce the power impact when line outage happens, thereby enhancing the resilience of DSs through forming feasible MGs after extreme events. (2) The proposed model optimizes the network topology prior to the event. Therefore, more flexible MG topology can be obtained to satisfy the supply-and-demand balance and more critical loads can be supplied. (3) The proposed method allows power flow on vulnerable lines before the outage. Compared with the preventive defensive islanding method, a secure and less conservative scheduling strategy can be obtained.
[1] 别朝红, 林雁翎, 邱爱慈. 弹性电网及其恢复力的基本概念与研究展望[J]. 电力系统自动化, 2015, 39(22): 1-9. Bie Zhaohong, Lin Yanling, Qiu Aici.Concept and research prospects of power system resilience[J]. Automation of Electric Power Systems, 2015, 39(22): 1-9. [2] Tan Yushi, Das A K, Arabshahi P, et al.Distribution systems hardening against natural disasters[J]. IEEE Transactions on Power Systems, 2018, 33(6): 6849-6860. [3] Wang Xu, Li Zhiyi, Shahidehpour M, et al.Robust line hardening strategies for improving the resilience of distribution systems with variable renewable resources[J]. IEEE Transactions on Sustainable Energy, 2019, 10(1): 386-395. [4] 尉耀稳, 李跃龙, 陈思超, 等. 多类型源储协调互动的配电网分布鲁棒优化调度[J]. 电力工程技术, 2021, 40(5): 192-199. Yu Yaowen, Li Yuelong, Chen Sichao, et al.Distributionally robust optimal dispatch of distribution network considering multiple source-storage coordinated interaction[J]. Electric Power Engineering Technology, 2021, 40(5): 192-199. [5] 姜云鹏, 任洲洋, 李秋燕, 等. 考虑多灵活性资源协调调度的配电网新能源消纳策略[J]. 电工技术学报, 2022, 37(7): 1820-1835. Jiang Yunpeng, Ren Zhouyang, Li Qiuyan, et al.An accommodation strategy for renewable energy in distribution network considering coordinated dispatching of multi-flexible resources[J]. Transactions of China Electrotechnical Society, 2022, 37(7): 1820-1835. [6] 倪萌, 王蓓蓓, 朱红, 等. 能源互联背景下面向高弹性的多元融合配电网双层分布式优化调度方法研究[J]. 电工技术学报, 2022, 37(1): 208-219. Ni Meng, Wang Beibei, Zhu Hong, et al.Study of two-layer distributed optimal scheduling strategy for highly elastic multi-resource fusion distribution network in energy interconnection environment[J]. Transactions of China Electrotechnical Society, 2022, 37(1): 208-219. [7] 许寅, 和敬涵, 王颖, 等. 韧性背景下的配网故障恢复研究综述及展望[J]. 电工技术学报, 2019, 34(16): 3416-3429. Xu Yin, He Jinghan, Wang Ying, et al.A review on distribution system restoration for resilience enhancement[J]. Transactions of China Electrotechnical Society, 2019, 34(16): 3416-3429. [8] 王钰山, 邓晖, 王旭, 等. 考虑台风时空演变的配电网移动储能优化配置与运行策略[J]. 电力系统自动化, 2022, 46(9): 42-51. Wang Yushan, Deng Hui, Wang Xu, et al.Optimal configuration and operation strategy of mobile energy storage in distribution network considering spatial-temporal evolution of typhoon[J]. Automation of Electric Power Systems, 2022, 46(9): 42-51. [9] Manshadi S D, Khodayar M E.Resilient operation of multiple energy carrier microgrids[J]. IEEE Transactions on Smart Grid, 2015, 6(5): 2283-2292. [10] Liu Jianzhe, Lu Xiaonan, Wang Jianhui.Resilience analysis of DC microgrids under denial of service threats[J]. IEEE Transactions on Power Systems, 2019, 34(4): 3199-3208. [11] Wang Zhaoyu, Chen Bokan, Wang Jianhui, et al.Networked microgrids for self-healing power systems[J]. IEEE Transactions on Smart Grid, 2016, 7(1): 310-319. [12] Ambia M N, Meng Ke, Xiao Weidong, et al.Nested formation approach for networked microgrid self-healing in islanded mode[J]. IEEE Transactions on Power Delivery, 2021, 36(1): 452-464. [13] Shen Feifan, Wu Qiuwei, Zhao Jin, et al.Distributed risk-limiting load restoration in unbalanced distribution systems with networked microgrids[J]. IEEE Transactions on Smart Grid, 2020, 11(6): 4574-4586. [14] Kim J, Dvorkin Y.Enhancing distribution system resilience with mobile energy storage and microgrids[J]. IEEE Transactions on Smart Grid, 2019, 10(5): 4996-5006. [15] Wang Zhaoyu, Wang Jianhui.Self-healing resilient distribution systems based on sectionalization into microgrids[J]. IEEE Transactions on Power Systems, 2015, 30(6): 3139-3149. [16] Chen Chen, Wang Jianhui, Qiu Feng, et al.Resilient distribution system by microgrids formation after natural disasters[J]. IEEE Transactions on Smart Grid, 2016, 7(2): 958-966. [17] 陈厚合, 丛前, 姜涛, 等. 多能协同的配电网供电恢复策略[J]. 电工技术学报, 2022, 37(3): 610-622, 685. Chen Houhe, Cong Qian, Jiang Tao, et al.Distribution systems restoration with multi-energy synergy[J]. Transactions of China Electrotechnical Society, 2022, 37(3): 610-622, 685. [18] 李振坤, 周伟杰, 王坚敏, 等. 基于风光荷功率曲线的有源配电网动态孤岛划分方法[J]. 电力系统自动化, 2016, 40(14): 58-64, 71. Li Zhenkun, Zhou Weijie, Wang Jianmin, et al.Dynamic islanding method of active power distribution network based on wind-photovoltaic-load curve[J]. Automation of Electric Power Systems, 2016, 40(14): 58-64, 71. [19] 张瑞曦, 徐青山, 程煜, 等. 极端灾害下考虑动态重构的微电网形成策略[J]. 电力工程技术, 2022, 41(1): 56-63. Zhang Ruixi, Xu Qingshan, Cheng Yu, et al.Microgrid formation strategy considering dynamic reconstruction under extreme disasters[J]. Electric Power Engineering Technology, 2022, 41(1): 56-63. [20] 詹红霞, 肖竣文, 邓小勇, 等. 计及柔性负荷的高比例风光渗透下配电网孤岛划分策略[J]. 电力工程技术, 2022, 41(4): 108-116. Zhan Hongxia, Xiao Junwen, Deng Xiaoyong, et al.Islanding strategy for distribution network with high proportion of wind/photovoltaic penetration considering flexible load[J]. Electric Power Engineering Technology, 2022, 41(4): 108-116. [21] Cai Sheng, Xie Yunyun, Wu Qiuwei, et al.Active and reactive power coordinated two-stage MG scheduling for resilient distribution systems under uncertainties[J]. IEEE Transactions on Smart Grid, 2022, 13(4): 2986-2998. [22] Panteli M, Trakas D N, Mancarella P, et al.Boosting the power grid resilience to extreme weather events using defensive islanding[J]. IEEE Transactions on Smart Grid, 2016, 7(6): 2913-2922. [23] Liu Jiancun, Qin Chao, Yu Yixin.Enhancing distribution system resilience with proactive islanding and RCS-based fast fault isolation and service restoration[J]. IEEE Transactions on Smart Grid, 2020, 11(3): 2381-2395. [24] Pandey S, Chanda S, Srivastava A K, et al.Resiliency-driven proactive distribution system reconfiguration with synchrophasor data[J]. IEEE Transactions on Power Systems, 2020, 35(4): 2748-2758. [25] Khodaei A.Resiliency-oriented microgrid optimal scheduling[J]. IEEE Transactions on Smart Grid, 2014, 5(4): 1584-1591. [26] Lee J, Lee S, Lee K.Multistage stochastic optimization for microgrid operation under islanding uncertainty[J]. IEEE Transactions on Smart Grid, 2021, 12(1): 56-66. [27] Amirioun M H, Aminifar F, Lesani H.Resilience-oriented proactive management of microgrids against windstorms[J]. IEEE Transactions on Power Systems, 2018, 33(4): 4275-4284. [28] Gholami A, Shekari T, Grijalva S.Proactive management of microgrids for resiliency enhancement: an adaptive robust approach[J]. IEEE Transactions on Sustainable Energy, 2019, 10(1): 470-480. [29] Tang Fen, Guerrero J M, Vasquez J C, et al.Distributed active synchronization strategy for microgrid seamless reconnection to the grid under unbalance and harmonic distortion[J]. IEEE Transactions on Smart Grid, 2015, 6(6): 2757-2769. [30] 贾冠龙, 陈敏, 赵斌, 等. 柔性多状态开关在智能配电网中的应用[J]. 电工技术学报, 2019, 34(8): 1760-1768. Jia Guanlong, Chen Min, Zhao Bin, et al.Application of flexible multi-state switch in intelligent distribution network[J]. Transactions of China Electrotechnical Society, 2019, 34(8): 1760-1768. [31] Babaei S, Jiang Ruiwei, Zhao Chaoyue.Distributionally robust distribution network configuration under random contingency[J]. IEEE Transactions on Power Systems, 2020, 35(5): 3332-3341. [32] Turitsyn K, Šulc P, Backhaus S, et al.Distributed control of reactive power flow in a radial distribution circuit with high photovoltaic penetration[C]//IEEE PES General Meeting, Minneapolis, MN, USA, 2010: 1-6. [33] Yeh H G, Gayme D F, Low S H.Adaptive VAR control for distribution circuits with photovoltaic generators[J]. IEEE Transactions on Power Systems, 2012, 27(3): 1656-1663. [34] Bassey O, Butler-Purry K L, Chen Bo. Dynamic modeling of sequential service restoration in islanded single master microgrids[J]. IEEE Transactions on Power Systems, 2020, 35(1): 202-214. [35] 郭力, 富晓鹏, 李霞林, 等. 独立交流微电网中电池储能与柴油发电机的协调控制[J]. 中国电机工程学报, 2012, 32(25): 70-78, 12. Guo Li, Fu Xiaopeng, Li Xialin, et al.Coordinated control of battery storage and diesel generators in isolated AC microgrid systems[J]. Proceedings of the CSEE, 2012, 32(25): 70-78, 12. [36] 张培高, 李兴源, 李政. 孤网频率稳定与控制策略研究[J]. 电力系统保护与控制, 2012, 40(15): 143-149, 155. Zhang Peigao, Li Xingyuan, Li Zheng.Research on frequency stability and control strategy in isolated power grid[J]. Power System Protection and Control, 2012, 40(15): 143-149, 155.
2023, Vol. 38 
