Distributed Hierarchical Cooperative Control and Stability Analysis of Flexible Interconnected Microgrid Cluster Via Back-to-Back Converters
Meng Xiaoxiao1, You Zehao1, Zhang Maofan2, Shao Bingbing1
1. Anhui Province Key Laboratory of Renewable Energy Utilization and Energy Saving Hefei University of Technology Hefei 230009 China; 2. Shibei Power Supply Branch of State Grid Chongqing Electric Power Company Chongqing 401147 China
Abstract：A single microgrid (MG) has a small capacity and poor stability problems. Combining multiple microgrids adjacent to each other in geographical space into a more compact whole, that is, microgrid cluster (MGC), is an effective way to improve the distributed power supply (DG) consumption level. The traditional interconnection mode has the defect that the disturbance between MG units cannot be isolated from each other, and the interactive power can only be adjusted indirectly. Although the flexible interconnection based on back-to-back converters (BTBC) has the advantages of inter-regional power flow continuous regulation and fault zone buffering, the flexible interconnection MGC system cannot form an effective “frequency signal” transmission among MG units. It is difficult to achieve active power sharing at the global level of microgrid clusters. The current MGC system based on BTBC interconnection has significant defects, mainly manifested as the lack of effective hierarchical cooperative control architecture design and stable dominant characteristics analysis under hierarchical cooperative control. A new control method based on the flexible interconnection of BTBC needs to be proposed. Firstly, this paper proposes a novel distributed hierarchical coordinated control architecture, including a physical layer of flexible interconnected microgrid cluster and an information layer with sparse communication in a two-layer structure. Under this control architecture, the control objectives can be realized, such as secondary restoration control, reactive power sharing control, and global active power sharing control for each DG frequency/port bounded voltage in the MG unit. Secondly, two control strategies are proposed to achieve global active power sharing. Local control is independent of communication but cannot be parallel with frequency invariant control, and hierarchical cooperative control depends on communication but can realize frequency invariant control at the same time. Thirdly, a full-order small signal model of the system is established, and the dominant modes are analyzed. Finally, Matlab/Simulink simulation is carried out to verify the effectiveness and superiority of the proposed control strategies. The conclusions are as follows. (1) Compared with the traditional hierarchical cooperative control and local control, the proposed strategy can achieve both MG frequency/voltage restorations and active/reactive power-sharing management. (2) The stable dominant modes of the proposed hierarchical cooperative control are the voltage and power angle dynamics in each MG. The stable dominant modes of local control are the dynamics in BTBCs. (3) The stability of the proposed hierarchical cooperative control strategy is close to the strategy mentioned in the literature [15]. It does not need to measure (or estimate) the local load in real-time, has no undefined solution problem, is easy to apply in practice.
[1] 郑重, 苗世洪, 李超, 等. 面向微型能源互联网接入的交直流配电网协同优化调度策略[J]. 电工技术学报, 2022, 37(1): 192-207. Zheng Zhong, Miao Shihong, Li Chao, et al.Coor-dinated optimal dispatching strategy of AC/DC distribution network for the integration of micro energy Internet[J]. Transactions of China Electro-technical Society, 2022, 37(1): 192-207. [2] 刘欣, 郭志博, 贾焦心, 等. 基于序阻抗的虚拟同步发电机并网稳定性分析及虚拟阻抗设计[J]. 电工技术学报, 2023, 38(15): 4130-4146. Liu Xin, Guo Zhibo, Jia Jiaoxin, et al.Stability analysis and virtual impedance design of virtual synchronous machine based on sequence impe-dance[J]. Transactions of China Electrotechnical Society, 2023, 38(15): 4130-4146. [3] 董雷, 杨子民, 乔骥, 等. 基于分层约束强化学习的综合能源多微网系统优化调度[J]. 电工技术学报, 2024, 39(5): 1436-1453. Dong Lei, Yang Zimin, Qiao Ji, et al.Optimal scheduling of integrated energy multi-microgrid system based on hierarchical constrained reinfor-cement learning[J]. Transactions of China Electro-technical Society, 2024, 39(5): 1436-1453. [4] 徐殿国, 刘瑜超, 武健. 多端直流输电系统控制研究综述[J]. 电工技术学报, 2015, 30(17): 1-12. Xu Dianguo, Liu Yuchao, Wu Jian.Review on control strategies of multi-terminal direct current trans-mission system[J]. Transactions of China Electro-technical Society, 2015, 30(17): 1-12. [5] 赵书强, 王慧, 田娜, 等. 基于模型预测控制的直流微电网虚拟惯性优化方法[J]. 电工技术学报, 2023, 38(12): 3264-3276. Zhao Shuqiang, Wang Hui, Tian Na, et al.Model predictive control based DC microgrid virtual inertia optimal method[J]. Transactions of China Electro-technical Society, 2023, 38(12): 3264-3276. [6] 王成山, 王丹, 周越. 智能配电系统架构分析及技术挑战[J]. 电力系统自动化, 2015, 39(9): 2-9. Wang Chengshan, Wang Dan, Zhou Yue.Framework analysis and technical challenges to smart distribution system[J]. Automation of Electric Power Systems, 2015, 39(9): 2-9. [7] Guan Yajuan, Wei Baoze, Guerrero J M, et al.An overview of the operation architectures and energy management system for multiple microgrid clusters[J]. iEnergy, 2022, 1(3): 306-314. [8] 陈倩, 王维庆, 王海云. 计及需求响应和混合博弈含多微网主动配电网协调优化[J]. 电力系统自动化, 2023, 47(9): 99-109. Chen Qian, Wang Weiqing, Wang Haiyun.Coor-dinated optimization of active distribution network with multiple microgrids considering demand response and mixed game[J]. Automation of Electric Power Systems, 2023, 47(9): 99-109. [9] 蔡瑶, 卢志刚, 潘尧, 等. 计及多重差异的交直流混合多能微网多时间尺度优化调度[J]. 电工技术学报, 2024, 39(11): 3392-3410. Cai Yao, Lu Zhigang, Pan Yao, et al.Multi-time-scale optimal scheduling of AC-DC hybrid multi-energy microgrid considering multiple differences[J]. Transa-ctions of China Electrotechnical Society, 2024, 39(11): 3392-3410. [10] 黄文焘, 吴攀, 邰能灵, 等. 基于混合公共连接单元的柔性互联多微网结构与控制方法[J]. 中国电机工程学报, 2019, 39(12): 3499-3514. Huang Wentao, Wu Pan, Tai Nengling, et al.Architecture design and control method for flexible connected multiple microgrids based on hybrid unit of common coupling[J]. Proceedings of the CSEE, 2019, 39(12): 3499-3514. [11] 王杰, 黄文焘, 余墨多, 等. 柔性互联微网模式紧急切换平滑控制策略[J]. 中国电机工程学报, 2022, 42(21): 7695-7706. Wang Jie, Huang Wentao, Yu Moduo, et al.Smooth control strategy for emergency switching of inter-connected microgrids via FMS[J]. Proceedings of the CSEE, 2022, 42(21): 7695-7706. [12] 杨万里, 涂春鸣, 兰征, 等. 基于储能型柔性多状态开关的直流微电网与交流配电网柔性互联策略[J]. 电力自动化设备, 2021, 41(5): 254-260. Yang Wanli, Tu Chunming, Lan Zheng, et al.Flexible interconnection strategy between DC microgrid and AC distribution network based on energy storage flexible multi-state switch[J]. Electric Power Auto-mation Equipment, 2021, 41(5): 254-260. [13] Zhao Daduan, Zhang Chenghui, Sun Yue, et al.Distributed robust frequency restoration and active power sharing for autonomous microgrids with event-triggered strategy[J]. IEEE Transactions on Smart Grid, 2021, 12(5): 3819-3834. [14] Li Zhongwen, Cheng Zhiping, Liang Jing, et al.Distributed event-triggered secondary control for economic dispatch and frequency restoration control of droop-controlled AC microgrids[J]. IEEE Transa-ctions on Sustainable Energy, 2020, 11(3): 1938-1950. [15] Wu Xiangyu, Xu Yin, He Jinghan, et al.Pinning-based hierarchical and distributed cooperative control for AC microgrid clusters[J]. IEEE Transactions on Power Electronics, 2020, 35(9): 9865-9885. [16] Lu Xiaoqing, Lai Jingang, Yu Xinghuo.A novel secondary power management strategy for multiple AC microgrids with cluster-oriented two-layer cooperative framework[J]. IEEE Transactions on Industrial Informatics, 2021, 17(2): 1483-1495. [17] 范培潇, 杨军, 温裕鑫, 等. 基于可进化模型预测控制的含电动汽车多微电网智能发电控制策略[J]. 电工技术学报, 2024, 39(3): 699-713. Fan Peixiao, Yang Jun, Wen Yuxin, et al.Intelligent generation control strategy of multi-microgrid with electric vehicles based on evolutionary model predictive control[J]. Transactions of China Elec-trotechnical Society, 2024, 39(3): 699-713. [18] 于国星, 宋蕙慧, 侯睿, 等. 柔性直流互联孤岛微网群的分布式频率协同控制[J]. 电力系统自动化, 2020, 44(20): 103-111. Yu Guoxing, Song Huihui, Hou Rui, et al.Distributed cooperative frequency control for flexible DC interconnected island microgrid cluster[J]. Auto-mation of Electric Power Systems, 2020, 44(20): 103-111. [19] Brandao D I, dos Santos R P, Silva W W A G, et al. Model-free energy management system for hybrid alternating current/direct current microgrids[J]. IEEE Transactions on Industrial Electronics, 2021, 68(5): 3982-3991. [20] 孟潇潇, 邵冰冰, 韩平平, 等. 基于背靠背变流器柔性互联的微网群分层协同恢复控制策略[J]. 中国电机工程学报, 2023, 43(20): 7812-7827. Meng Xiaoxiao, Shao Bingbing, Han Pingping, et al.Hierarchical cooperative recovery control strategy for flexible interconnected microgrid cluster based on back-to-back converters[J]. Proceedings of the CSEE. 2023, 43(20): 7812-7826. [21] He Jinghan, Wu Xiaoyu, Wu Xiangyu, et al.Small-signal stability analysis and optimal parameters design of microgrid clusters[J]. IEEE Access, 2019, 7: 36896-36909. [22] Naderi M, Khayat Y, Shafiee Q, et al.Interconnected autonomous AC microgrids via back-to-back con-verters: part I: small-signal modeling[J]. IEEE Transa-ctions on Power Electronics, 2020, 35(5): 4728-4740. [23] Naderi M, Khayat Y, Shafiee Q, et al.Interconnected autonomous AC microgrids via back-to-back con-verters: part II: stability analysis[J]. IEEE Transa-ctions on Power Electronics, 2020, 35(11): 11801-11812. [24] 周念成, 张茂凡, 孟潇潇, 等. 基于背靠背变流器互联的微网间传输功率控制及稳定性分析[J]. 电力系统自动化, 2023, 47(2): 34-41. Zhou Niancheng, Zhang Maofan, Meng Xiaoxiao, et al.Control and stability analysis of power trans-mission between microgrids based on back-to-back converter interconnection[J]. Automation of Electric Power Systems, 2023, 47(2): 34-41. [25] 田艳军, 彭飞, 王毅, 等. AC/DC-DC/AC级联变流器DC与AC双侧双向交互稳定性分析及协调优化控制[J]. 高电压技术, 2021, 47(7): 2434-2446. Tian Yanjun, Peng Fei, Wang Yi, et al.Bidirectional interactive stability analysis of DC and AC sides for AC/DC-DC/AC cascade converter and coordinative optimization control[J]. High Voltage Engineering, 2021, 47(7): 2434-2446. [26] Lai Jingang, Lu Xiaoqing, Yu Xinghuo, et al.Cluster-oriented distributed cooperative control for multiple AC microgrids[J]. IEEE Transactions on Industrial Informatics, 2019, 15(11): 5906-5918. [27] Lu Xiaoqing, Lai Jingang, Liu Guoping.Master-slave cooperation for multi-DC-MGs via variable cyber networks[J]. IEEE Transactions on Cybernetics, 2021, 52(8): 8425-8438. [28] 邵冰冰, 赵峥, 肖琪, 等. 多直驱风机经柔直并网系统相近次同步振荡模式参与因子的弱鲁棒性分析[J]. 电工技术学报, 2023, 38(3): 754-769. Shao Bingbing, Zhao Zheng, Xiao Qi, et al.Weak robustness analysis of close subsynchronous oscillation Modes’Participation factors in multiple direct-drive wind turbines with the VSC-HVDC system[J]. Transactions of China Electrotechnical Society, 2023, 38(3): 754-769. [29] 张泽华, 宋桂英, 张晓璐, 等. 考虑恒功率负载的直流微电网稳定性与鲁棒性控制策略[J]. 电工技术学报, 2023, 38(16): 4391-4405. Zhang Zehua, Song Guiying, Zhang Xiaolu, et al.Stability and robustness control strategy of DC microgrid considering constant power load[J]. Transa-ctions of China Electrotechnical Society, 2023, 38(16): 4391-4405. [30] 王力, 谭振杰, 曾祥君, 等. 基于改进等效电路模型的直流微电网大信号稳定性分析[J]. 电工技术学报, 2024, 39(5): 1284-1299. Wang Li, Tan Zhenjie, Zeng Xiangjun, et al.Large signal stability analysis of DC microgrid based on improved equivalent circuit model[J]. Transactions of China Electrotechnical Society, 2024, 39(5): 1284-1299.
2024, Vol. 39 
