-
IDC的直流负荷比重增大,柔性配用电技术可提高IDC可再生能源消纳能力,进一步降低IDC能源效率的指标;使输配电系统转变为灵活的、可主动运行的“智能”结构,为IDC提供新型、高效的动力保障,减少电能变换损耗,提高用能效率,提供可靠、稳定、高质量的电能。柔性技术在IDC输配电系统中的应用包括两个方面,一是利用柔性电力电子设备进行功率传输、电压转换及电能质量改善;二是应用柔性技术实现的柔性交直流输电。因此,柔性技术对输配电系统的优化亦需要根据两方面来讨论。
首先,柔性电力电子设备对IDC配网的优化可总结为如下几点[59]:
1)降低采购成本
相较于传统配网设备,由于半导体器件生产技术的巨大发展,这些以半导体为基础的柔性电力电子器件已经实现了大规模量产,价格更低,并有多种规格可供选择。
2)高效快速
在大多数应用中,柔性设备是作为开关来使用。在开关的两种模式下,柔性设备的功率损耗非常小,开关损耗也非常低。此外,与传统配网中的机械或机电设备相比,应用柔性设备的输配电系统有更快的动态响应。
3)降低尺寸和占地面积
与类似额定功率的传统设备相比,柔性设备体积普遍很小,因此重量更轻,占地面积更小,需要处理的问题更少,降低了安装、包装和运输成本。
柔性交直流输电对IDC配网的优化也可以总结为如下4点[60]:
1)高兼容性和可靠性
柔性直流输电网络可以更好地兼容储能设备,提高供电系统的可靠性及故障恢复能力;同时,考虑到IDC大多为直流负荷,直流供电会大幅降低电压和电流纹波对负荷的影响。
2)低损耗高效率能量传输
相较于交流线路中因为线缆护套涡流产生的有功和无功损耗,直流输电线路可有效降低传输损耗,可有效提高能量传输效率。
3)提高供电容量和半径
根据潮流公式,在相同的导线截面、绝缘水平及电流密度情况下,功率传输容量直流线路约为交流线路的1.5倍。因此,柔性直流供电可在相同的线路建设费用及占地面积情况下传输更高功率。
4)更方便的分布式电源接入
对以光伏为代表的分布式电源来说,直接利用直流接入输电网络可降低对接口设备和控制技术的要求。这样,对于直流输电系统,分布式电源将可以更灵活更方便地接入。
-
根据上述讨论,文章筛选出柔性配用电技术在IDC应用的3种技术路线:整流输配电、直流输配电以及交直流混合供配电。下面将分别讨论并进行比较。
-
整流输配电结构如图2所示。380 V交流电通过柔性设备转为240 V直流,供给蓄电池和机房列头柜使用。该路线可减少中间电能变换环节,大幅提高供电效率;采用模块化设计,可保持AC/DC处于较高的转换效率;整流模块并联,提高供电的安全和可靠性;采用移相变压器取代工频变压器,省去功率因数调整,提高效率。但是,由于缺乏直流接口,该方案不适用于新能源灵活接入。
-
直流输配电结构如图3所示。该方案由外部两路±10 kV直流输入,采用直流断路器互联,互为备用;采用纯直流输配电,输电容量大,节约线缆投资。供电过程中电压稳定性好,无谐波问题;同时,该方案采用多变换器协调控制,实现能量精准管理。
但是,直流输配电也有一些问题和不足,首先,基于模块化多电平控制(Modular Multi-level Control, MMC)的直流变压器所需子模块和器件数目很多,成本高;其次,直流变压器模块数目校对较少,功率密度相对较高,容易造成危险;最后,现有工程用直流变压器多采用两级结构,前级增加额外损耗和成本,降低系统效率;功率模块多采用双有源桥(Dual Active Bridge,DAB)或CLLC谐振电路,DAB开关损耗较大,非正弦电流存在电磁干扰;CLLC谐振变换器具备自然零压零流特性,但需要两组谐振电容。
-
随着柔性配用电技术的发展进步,交/直流混合输配电网被提出。该方案结构如图4所示。其中AC/DC模块采用级联H桥(Cascaded H-Bridge,CHB)+DAB拓扑,减少一级变换,提高供电效率2%;AC/DC模块体积小,节约用地资源;此外,还具备谐波治理、无功补偿、三相不平衡治理功能;AC/DC模块提供灵活的交直流接口,方便新能源的接入与就地消纳。
相较于前两种路线方案,该方案兼容交直流供电,可提高系统效率;减小了系统复杂度,有利于系统的稳定控制;可实现功率互动,进行交直支撑,提升系统可靠性;交直流混联可解决不同电源、不同负荷友好接入外部交直流电源完全无耦合,提高供电独立性。
3种技术路线各有优劣,需结合IDC的选址及其性能要求,因地制宜地采用。整流输配电是适应性较广的低压侧解决方案,但不适用于新能源灵活接入;直流输配电是技术优势最高的中低压解决方案,有现成的直流网络最佳,可节省造价;交直流混合输配电是目前较为合适的中间路线,可直接采用相对成熟的分布式互补能源/储能系统/柔性电网技术。3种不同技术路线的其他特点总结于表1[61]。
Application and Prospect of Flexible Transmission and Distribution Technology in Internet Data Center
-
摘要:
目的 作为我国“新基建”的重要推力,互联网数据中心迎来蓬勃发展的机遇,成为新增用能领域,对所在地配电网的供电水平和能力提出了更高要求。柔性输配电技术和关键设备的创新应用,让供配电系统更智能、更灵活、更可靠,更能够应对互联网数据中心这类直流负载占比大、集中的高载能负荷所带来挑战,实现互联网数据中心建设运营更低碳、更高效、更可靠、更经济。 方法 首先讨论了互联网数据中心负荷的基本需求,同时分析了互联网数据中心整体的分级和性能需求,研究了柔性技术在配用电网络中的应用,着重分析并比较了“整流配电、直流配电、交直流混合供配电”3类技术路线。 结果 为系统可靠性、稳定性、电能质量、用电效率和接纳新能源等方面的问题提供了因地制宜的解决方案。 结论 通过总结归纳已有的研究成果可知,柔性输配电技术是建设互联网数据中心的核心技术。应从器件、算法等不同方面研究有针对性的数据中心控制方案。文章在对不同方面的研究成果进行综述后,还对头型输配电技术在互联网数据中心中的实践及推广进行了展望。 Abstract:Introduction As an important thrust of China's "new infrastructure", internet data centers have ushered in opportunities for vigorous development and become new areas of energy use, putting forward higher requirements for the power supply level and capacity of the local distribution network. The innovative application of flexible transmission and distribution technology and key equipment makes the power supply and distribution system more intelligent, more flexible and more reliable, and more able to cope with the challenges brought by the large proportion of DC loads and concentrated high-load energy loads such as Internet data centers, and realize the construction and operation of Internet data centers more low-carbon, more efficient, more reliable and more economical. Method Firstly, the basic load requirements of Internet data center were discussed, the overall classification and performance requirements of internet data centers were analyzed. The application of flexible technology in distribution network was studied, with a focus on analyzing and comparing three types of technical routes: "rectification distribution, DC distribution, and AC-DC hybrid power supply and distribution". Result The paper provides provides tailored solutions for issues related to system reliability, stability, power quality, power efficiency and acceptance of new energy. Conclusion By summarizing the existing research results, flexible transmission and distribution technology is regarded as the core technology of building internet data center. Targeted data center control scheme should be studied from different aspects such as device and algorithms. After summarizing the research results of different aspects, the paper also looks forward to the practice and popularization of head-to-head transmission and distribution technology in internet data center. -
[1] 王成山, 宋关羽, 李鹏, 等. 基于智能软开关的智能配电网柔性互联技术及展望 [J]. 电力系统自动化, 2016, 40(22): 168-175. DOI: 10.7500/AEPS20160620009. WANG C S, SONG G Y, LI P, et al. Research and prospect for soft open point based flexible interconnection technology for smart distribution network [J]. Automation of electric power systems, 2016, 40(22): 168-175. DOI: 10.7500/AEPS20160620009. [2] AITHAL A, LI G, WU J Z. Grid side unbalanced fault detection using soft open point in an electrical distribution network [J]. Energy procedia, 2017, 105: 2859-2864. DOI: 10.1016/j.egypro.2017.03.631. [3] KARWATZKI D, BARUSCHKA L, MERTENS A. Survey on the Hexverter topology: a modular multilevel AC/AC converter [C]//The Korean Institute of Power Eletronics. 2015 9th International Conference on Power Electronics and ECCE Asia (ICPE-ECCE Asia), Seoul, Korea (South), June 1-5, 2015. New York, USA: IEEE, 2015: 1075-1082. DOI: 10.1109/ICPE.2015.7167914. [4] 张勇军, 羿应棋, 李立浧, 等. 双碳目标驱动的新型低压配电系统技术展望 [J]. 电力系统自动化, 2022, 46(22): 1-12. DOI: 10.7500/AEPS20210922006. ZHANG Y J, YI Y Q, LI L C, et al. Prospect of new low-voltage distribution system technology driven by carbon emission peak and carbon neutrality targets [J]. Automation of electric power systems, 2022, 46(22): 1-12. DOI: 10.7500/AEPS20210922006. [5] HOSSEINIPOUR A, HOJABRI H. Virtual inertia control of PV systems for dynamic performance and damping enhancement of DC microgrids with constant power loads [J]. IET renewable power generation, 2018, 12(4): 430-438. DOI: 10.1049/iet-rpg.2017.0468. [6] 拓超群, 贺之渊, 徐千鸣, 等. 直流电网潮流控制器研究与应用综述 [J]. 电力系统自动化, 2022, 46(6): 173-183. DOI: 10.7500/AEPS20210310001. TUO C Q, HE Z Y, XU Q M, et al. Review on research and application of power flow controller of DC grid [J]. Automation of electric power systems, 2022, 46(6): 173-183. DOI: 10.7500/AEPS20210310001. [7] 沙广林, 刘斌, 邬玮晗, 等. 多端柔性互联的交直流配电系统分层控制策略 [J]. 高电压技术, 2020, 46(10): 3509-3520. DOI: 10.13336/j.1003-6520.hve.20200414. SHA G L, LIU B, WU W H, et al. Hierarchical control strategy for multi-terminal flexible interconnected AC/DC power distribution systems [J]. High voltage engineering, 2020, 46(10): 3509-3520. DOI: 10.13336/j.1003-6520.hve.20200414. [8] 杨晓峰, 郑琼林, 林智钦, 等. 用于直流电网的大容量DC/DC变换器研究综述 [J]. 电网技术, 2016, 40(3): 670-677. DOI: 10.13335/j.1000-3673.pst.2016.03.002. YANG X F, ZHENG Q L, LIN Z Q, et al. Survey of high-power DC/DC converter for HVDC grid application [J]. Power system technology, 2016, 40(3): 670-677. DOI: 10.13335/j.1000-3673.pst.2016.03.002. [9] 肖先勇, 郑子萱. “双碳”目标下新能源为主体的新型电力系统: 贡献、关键技术与挑战 [J]. 工程科学与技术, 2022, 54(1): 47-59. DOI: 10.15961/j.jsuese.202100656. XIAO X Y, ZHENG Z X. New power systems dominated by renewable energy towards the goal of emission peak & carbon neutrality: contribution, key techniques, and challenges [J]. Advanced engineering sciences, 2022, 54(1): 47-59. DOI: 10.15961/j.jsuese.202100656. [10] 马钊, 赵志刚, 孙媛媛, 等. 新一代低压直流供用电系统关键技术及发展展望 [J]. 电力系统自动化, 2019, 43(23): 12-22. DOI: 10.7500/AEPS20190905007. MA Z, ZHAO Z G, SUN Y Y, et al. Key technologies and development prospect of new generation low-voltage DC power supply and utilization system [J]. Automation of electric power systems, 2019, 43(23): 12-22. DOI: 10.7500/AEPS20190905007. [11] 王成山, 李鹏, 于浩. 智能配电网的新形态及其灵活性特征分析与应用 [J]. 电力系统自动化, 2018, 42(10): 13-21. DOI: 10.7500/AEPS20171012002. WANG C S, LI P, YU H. Development and characteristic analysis of flexibility in smart distribution network [J]. Automation of electric power systems, 2018, 42(10): 13-21. DOI: 10.7500/AEPS20171012002. [12] 韩民晓, 谢文强, 曹文远, 等. 中压直流配电网应用场景与系统设计 [J]. 电力系统自动化, 2019, 43(23): 2-11. DOI: 10.7500/AEPS20190320004. HAN M X, XIE W Q, CAO W Y, et al. Application scenarios and system design of medium-voltage DC distribution network [J]. Automation of electric power systems, 2019, 43(23): 2-11. DOI: 10.7500/AEPS20190320004. [13] 史清芳, 徐习东, 赵宇明. 电力电子设备对直流配电网可靠性影响 [J]. 电网技术, 2016, 40(3): 725-732. DOI: 10.13335/j.1000-3673.pst.2016.03.010. SHI Q F, XU X D, ZHAO Y M. Effects of power electronic devices on DC distribution reliability [J]. Power system technology, 2016, 40(3): 725-732. DOI: 10.13335/j.1000-3673.pst.2016.03.010. [14] 李兴源, 曾琦, 王渝红, 等. 柔性直流输电系统控制研究综述 [J]. 高电压技术, 2016, 42(10): 3025-3037. DOI: 10.13336/j.1003-6520.hve.20160926001. LI X Y, ZENG Q, WANG Y H, et al. Control strategies of voltage source converter based direct current transmission system [J]. High voltage engineering, 2016, 42(10): 3025-3037. DOI: 10.13336/j.1003-6520.hve.20160926001. [15] 王博, 路俊海, 郭小江, 等. 多VSC型换流器电力系统潮流计算方法研究 [J]. 电网技术, 2016, 40(8): 2344-2349. DOI: 10.13335/j.1000-3673.pst.2016.08.014. WANG B, LU J H, GUO X J, et al. Load flow analysis for power system with multi-VSC based converter [J]. Power system technology, 2016, 40(8): 2344-2349. DOI: 10.13335/j.1000-3673.pst.2016.08.014. [16] PETROWSKI A. A clearing procedure as a niching method for genetic algorithms [C]//Proceedings of IEEE International Conference on Evolutionary Computation, Nagoya, Japan, May 20-22, 1996. New York, USA: IEEE, 1996: 798-803. DOI: 10.1109/ICEC.1996.542703. [17] WANG J C, WU B, XU D W, et al. Multimodular matrix converters with sinusoidal input and output waveforms [J]. IEEE transactions on industrial electronics, 2012, 59(1): 17-26. DOI: 10.1109/TIE.2011.2130506. [18] RAHBAR K, CHAI C C, ZHANG R. Energy cooperaion otimization in microgrids with renewable energy integration [J]. IEEE transactons on smat grid, 2018, 9(2): 1482-1493. DOI: 10.1109/TSG.2016.2600863. [19] 董朝阳, 赵俊华, 文福拴, 等. 从智能电网到能源互联网: 基本概念与研究框架 [J]. 电力系统自动化, 2014, 38(15): 1-11. DOI: 10.7500/AEPS20140613007. DONG Z Y, ZHAO J J, WEN F S, et al. From smart grid to energy internet: basic concept and research framework [J]. Automation of electric power systems, 2014, 38(15): 1-11. DOI: 10.7500/AEPS20140613007. [20] DAYARATHNA M, WEN Y G, FAN R. Data center energy consumption modeling: a survey [J]. IEEE communications surveys & tutorials, 2016, 18(1): 732-794. DOI: 10.1109/COMST.2015.2481183. [21] 姚钢, 茆中栋, 殷志柱, 等. 楼宇直流配电系统关键技术研究综述 [J]. 电力系统保护与控制, 2019, 47(15): 156-170. DOI: 10.7667/PSPC20191521. YAO G, MAO Z D, YIN Z Z, et al. Key technologies of building DC power distribution system: an overview [J]. Power system protection and control, 2019, 47(15): 156-170. DOI: 10.7667/PSPC20191521. [22] 张勇军, 陈泽兴, 蔡泽祥, 等. 新一代信息能源系统: 能源互联网 [J]. 电力自动化设备, 2016, 36(9): 1-7,16. DOI: 10.16081/j.issn.1006-6047.2016.09.001. ZHANG Y J, CHEN Z X, CAI Z X, et al. New generation of cyber-energy system: energy internet [J]. Electric power automation equipment, 2016, 36(9): 1-7,16. DOI: 10.16081/j.issn.1006-6047.2016.09.001. [23] 李丹, 陈贵海, 任丰原, 等. 数据中心网络的研究进展与趋势 [J]. 计算机学报, 2014, 37(2): 259-274. DOI: 10.3724/SP.J.1016.2014.00259. LI D, CHEN G H, REN F Y, et al. Data center network research progress and trends [J]. Chinese journal of computers, 2014, 37(2): 259-274. DOI: 10.3724/SP.J.1016.2014.00259. [24] 吴刚, 高赐威, 陈宋宋, 等. 考虑需求响应的数据中心用电负荷优化研究综述 [J]. 电网技术, 2018, 42(11): 3782-3788. DOI: 10.13335/j.1000-3673.pst.2018.0263. WU G, GAO C W, CHEN S S, et al. A survey on data center power load optimization considering demand response [J]. Power system technology, 2018, 42(11): 3782-3788. DOI: 10.13335/j.1000-3673.pst.2018.0263. [25] 周京华, 吴杰伟, 陈亚爱, 等. 张北阿里云互联网数据中心柔性直流输配电系统 [J]. 电气应用, 2019, 38(1): 54-58. ZHOU J H, WU J W, CHEN Y A, et al. Zhangbei Alicloud data center flexible DC transmission and distribution system [J]. Electrotechnical application, 2019, 38(1): 54-58. [26] 张勇军, 刘子文, 宋伟伟, 等. 直流配电系统的组网技术及其应用 [J]. 电力系统自动化, 2019, 43(23): 39-49. DOI: 10.7500/AEPS20190529001. ZHANG Y J, LIU Z W, SONG W W, et al. Networking technology and its application of DC distribution system [J]. Automation of electric power systems, 2019, 43(23): 39-49. DOI: 10.7500/AEPS20190529001. [27] 曾永浩, 叶家雄, 潘志图, 等. 含多端柔性多状态开关的主动配电网动态潮流 [J]. 广东电力, 2020, 33(5): 60-67. DOI: 10.3969/j.issn.1007-290X.2020.005.008. ZENG Y H, YE J X, PAN Z T, et al. Dynamic power flow analysis of active distribution network with multi-terminal flexible distribution switch [J]. Guangdong electric power, 2020, 33(5): 60-67. DOI: 10.3969/j.issn.1007-290X.2020.005.008. [28] 中华人民共和国住房和城乡建设部, 中华人民共和国国家质量监督检验检疫总局. 数据中心设计规范: GB 50174-2017 [S]. 北京: 中国计划出版社, 2017. Ministry of Housing and Urban-Rural Development of the People's Republic of China, General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. Code for design of data centers: GB 50174-2017 [S]. Beijing: China Planning Press, 2017. [29] 霍群海, 粟梦涵, 吴理心, 等. 柔性多状态开关新型复合控制策略 [J]. 电力系统自动化, 2018, 42(7): 166-170. DOI: 10.7500/AEPS20170808011. HUO Q H, SU M H, WU L X, et al. Compound control strategy for flexible multi-state switch [J]. Automation of electric power systems, 2018, 42(7): 166-170. DOI: 10.7500/AEPS20170808011. [30] 郑建平, 陈建福, 刘尧, 等. 基于柔性直流配电网的城市能源互联网 [J]. 南方电网技术, 2021, 15(1): 25-32. DOI: 10.13648/j.cnki.issn1674-0629.2021.01.004. ZHENG J P, CHEN J F, LIU Y, et al. Urban energy internet based on flexible DC distribution network [J]. Southern power system technology, 2021, 15(1): 25-32. DOI: 10.13648/j.cnki.issn1674-0629.2021.01.004. [31] 宋强, 赵彪, 刘文华, 等. 智能直流配电网研究综述 [J]. 中国电机工程学报, 2013, 33(25): 9-19. DOI: 10.13334/j.0258-8013.pcsee.2013.25.009. SONG Q, ZHAO B, LIU W H, et al. An overview of research on smart DC distribution power network [J]. Proceedings of the CSEE, 2013, 33(25): 9-19. DOI: 10.13334/j.0258-8013.pcsee.2013.25.009. [32] 杨欢, 蔡云旖, 屈子森, 等. 配电网柔性开关设备关键技术及其发展趋势 [J]. 电力系统自动化, 2018, 42(7): 153-165. DOI: 10.7500/AEPS20171031018. YANG H, CAI Y Y, QU Z S, et al. Key techniques and development trend of soft open point for distribution network [J]. Automation of electric power systems, 2018, 42(7): 153-165. DOI: 10.7500/AEPS20171031018. [33] 杨景刚, 刘洋, 刘瑞煌, 等. 基于模块化多电平换流器的多端口谐振型电力电子变压器 [J]. 电力系统自动化, 2020, 44(13): 123-134. DOI: 10.7500/AEPS20191108001. YANG J G, LIU Y, LIU R H, et al. Multi-port resonant power electronic transformer based on modular multilevel converter [J]. Automation of electric power systems, 2020, 44(13): 123-134. DOI: 10.7500/AEPS20191108001. [34] 张勇军, 刘斯亮, 江金群, 等. 低压智能配电网技术研究综述 [J]. 广东电力, 2019, 32(1): 1-12. DOI: 10.3969/j.issn.1007-290X.2019.001.001. ZHANG Y J, LIU S L, JIANG J Q, et al. Research review on low-voltage intelligent distribution network technology [J]. Guangdong electric power, 2019, 32(1): 1-12. DOI: 10.3969/j.issn.1007-290X.2019.001.001. [35] CASEIRO L, MENDES A. Fault analysis and non-redundant fault tolerance in 3-level double conversion UPS systems using finite-control-set model predictive control [J]. Energies, 2020, 14(8): 2210. DOI: 10.3390/en14082210. [36] 罗亮, 吴文峻, 张飞. 面向云计算数据中心的能耗建模方法 [J]. 软件学报, 2014, 25(7): 1371-1387. DOI: 10.13328/j.cnki.jos.004604. LUO L, WU W J, ZHANG F. Energy modeling based on cloud data center [J]. Journal of software, 2014, 25(7): 1371-1387. DOI: 10.13328/j.cnki.jos.004604. [37] PAKBAZNIA E, PEDRAM M. Minimizing data center cooling and server power costs [C]//Proceedings of 2009 ACM/IEEE International Symposium on Low Power Electronics and Design, San Fancisco, CA, USA, August 19-21, 2009. New York, USA: Association for Computing Machinery, 2009: 145-150. DOI: 10.1145/1594233.1594268. [38] HELLER B, SEETHARAMAN S, MAHADEVAN P, et al. ElasticTree: saving energy in data center networks [C]//Proceedings of the 7th USENIX Conference on Networked Systems Design and Implementation, San Jose, CA, USA, April 28-30, 2010. Berkeley, CA, USA: USENIX Association, 2010: 17. [39] ZAHARIA M, BORTHAKUR D, SEN SARMA J, et al. Delay scheduling: a simple technique for achieving locality and fairness in cluster scheduling [C]//Proceedings of the 5th European Conference on Computer Systems, Paris, France, April 13-16, 2010. New York, USA: Association for Computing Machinery, 2010: 265-278. DOI: 10.1145/1755913.1755940. [40] RAO L, LIU X, XIE L, et al. Minimizing electricity cost: optimization of distributed internet data centers in a multi-electricity-market environment [C]//Proceedings of 2010 IEEE INFOCOM, San Diego, CA, USA, March 14-19, 2010. New York, USA: IEEE, 2010: 1-9. DOI: 10.1109/INFCOM.2010.5461933. [41] SHAO H J, RAO L, WANG Z, et al. Optimal load balancing and energy cost management for internet data centers in deregulated electricity markets [J]. IEEE transactions on parallel and distributed systems, 2014, 25(10): 2659-2669. DOI: 10.1109/TPDS.2013.227. [42] YU L, JIANG T, CAO Y, et al. Risk-constrained operation for internet data centers in deregulated electricity markets [J]. IEEE transactions on parallel and distributed systems, 2014, 25(5): 1306-1316. DOI: 10.1109/TPDS.2013.2297095. [43] ZHANG Y W, WANG Y F, WANG X R. Electricity bill capping for cloud-scale data centers that impact the power markets [C]//Proceedings of the 2012 41st International Conference on Parallel Processing, Pittsburgh, PA, USA, September 10-13, 2012. New York, USA: IEEE, 2012: 440-449. DOI: 10.1109/ICPP.2012.23. [44] 李剑飞. 分布式光通信网络环境下能耗技术研究 [D]. 北京: 北京邮电大学, 2013. LI J F. Research on energy consumption of distributed optical communication network [D]. Beijing: Beijing University of Posts and Telecommunications, 2013. [45] WANG L Z, VON LASZEWSKI G, DAYAL J, et al. Thermal aware workload scheduling with backfilling for green data centers [C]//Proceedings of the 2009 IEEE 28th International Performance Computing and Communications Conference, Scottsdale, AZ, USA, December 14-16, 2009. New York, USA: IEEE, 2009: 289-296. DOI: 10.1109/PCCC.2009.5403821. [46] 黄仁乐, 蒲天骄, 刘克文, 等. 城市能源互联网功能体系及应用方案设计 [J]. 电力系统自动化, 2015, 39(9): 26-33. DOI: 10.7500/AEPS20141229010. HUANG R L, PU T J, LIU K W, et al. Design of hierarchy and functions of regional Energy Internet and its demonstration applications [J]. Automation of electric power systems, 2015, 39(9): 26-33. DOI: 10.7500/AEPS20141229010. [47] 秦红霞, 王成山, 刘树, 等. 智能微网与柔性配网相关技术探讨 [J]. 电力系统保护与控制, 2016, 44(20): 17-23. DOI: 10.7667/PSPC201663. QIN H X, WANG C S, LIU S, et al. Discussion on the technology of intelligent micro-grid and flexible distribution system [J]. Power system protection and control, 2016, 44(20): 17-23. DOI: 10.7667/PSPC201663. [48] QI Q, WU J Z, LONG C. Multi-objective operation optimization of an electrical distribution network with soft open point [J]. Applied energy, 2017, 208: 734-744. DOI: 10.1016/j.apenergy.2017.09.075. [49] CAO W Y, WU J Z, JENKINS N, et al. Benefits analysis of soft open points for electrical distribution network operation [J]. Applied energy, 2016, 165: 36-47. DOI: 10.1016/j.apenergy.2015.12.022. [50] QI Q, WU J Z. Increasing distributed generation penetration using network reconfiguration and soft open points [J]. Energy procedia, 2017, 105: 2169-2174. DOI: 10.1016/j.egypro.2017.03.612. [51] 王成山, 宋关羽, 李鹏, 等. 一种联络开关和智能软开关并存的配电网运行时序优化方法 [J]. 中国电机工程学报, 2016, 36(9): 2315-2321. DOI: 10.13334/j.0258-8013.pcsee.2016.09.001. WANG C S, SONG G Y, LI P, et al. A hybrid optimization method for distribution network operation with SNOP and tie switch [J]. Proceedings of the CSEE, 2016, 36(9): 2315-2321. DOI: 10.13334/j.0258-8013.pcsee.2016.09.001. [52] NABAVI-NIAKI A, IRAVANI M R. Steady-state and dynamic models of unified power flow controller (UPFC) for power system studies [J]. IEEE transactions on power systems, 1996, 11(4): 1937-1943. DOI: 10.1109/59.544667. [53] BENADJA M, REZKALLAH M, BENHALIMA S, et al. Hardware testing of sliding mode controller for improved performance of VSC-HVDC based offshore wind farm under DC fault [J]. IEEE transactions on industry applications, 2019, 55(2): 2053-2063. DOI: 10.1109/TIA.2018.2878539. [54] 王成山, 宋关羽, 李鹏, 等. 考虑分布式电源运行特性的有源配电网智能软开关SOP规划方法 [J]. 中国电机工程学报, 2017, 37(7): 1889-1896. DOI: 10.13334/j.0258-8013.pcsee.152649. WANG C S, SONG G Y, LI P, et al. Optimal configuration of soft open point for active distribution network considering the characteristics of distributed generation [J]. Proceedings of the CSEE, 2017, 37(7): 1889-1896. DOI: 10.13334/j.0258-8013.pcsee.152649. [55] 王成山, 孙充勃, 李鹏, 等. 基于SNOP的配电网运行优化及分析 [J]. 电力系统自动化, 2015, 39(9): 85-87. DOI: 10.7500/AEPS20140828002. WANG C S, SUN C B, LI P, et al. SNOP-based operation optimization and analysis of distribution networks [J]. Automation of electric power systems, 2015, 39(9): 85-87. DOI: 10.7500/AEPS20140828002. [56] 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. DOI: 10.3969/j.issn.1000-6753.2015.17.001. XU D G, LIU Y C, WU J. Review on control strategies of multi-terminal direct current transmission system [J]. Transactions of china electrotechnical society, 2015, 30(17): 1-12. DOI: 10.3969/j.issn.1000-6753.2015.17.001. [57] 赵波, 王财胜, 周金辉, 等. 主动配电网现状与未来发展 [J]. 电力系统自动化, 2014, 38(18): 125-135. DOI: 10.7500/AEPS20131218007. ZHAO B, WANG C S, ZHOU J H, et al. Present and future development trend of active distribution network [J]. Automation of electric power systems, 2014, 38(18): 125-135. DOI: 10.7500/AEPS20131218007. [58] KARWATZKI D, BARUSCHKA L, VON HOFEN M, et al. Branch energy control for the modular multilevel direct converter Hexverter [C]//2014 IEEE Energy Conversion Congress and Exposition (ECCE), Pittsburgh, PA, USA, September 14-18, 2014. New York, USA: IEEE, 2014: 1613-1622. DOI: 10.1109/ECCE.2014.6953611. [59] FAN B R, WANG K, LI Y D, et al. A branch energy control method based on optimized neutral-point voltage injection for a hexagonal modular multilevel direct converter (Hexverter) [C]//2015 18th International Conference on Electrical Machines and Systems (ICEMS), Pattaya, Thailand, October 25-28, 2015. New York, USA: IEEE, 2015: 1889-1893. DOI: 10.1109/ICEMS.2015.7385348. [60] 晏阳, 廖清芬, 刘涤尘, 等. 基于潮流介数的SNOP配置及主动配电系统优化 [J]. 南方电网技术, 2015, 9(11): 92-98. DOI: 10.13648/j.cnki.issn1674-0629.2015.11.014. YAN Y, LIAO Q F, LIU D C, et al. Power flow betweenness based SNOP allocation and active distribution network optimization [J]. Southern power system technology, 2015, 9(11): 92-98. DOI: 10.13648/j.cnki.issn1674-0629.2015.11.014. [61] 陆子凯, 简翔浩, 张明瀚. 多端柔性直流配电网的可靠性和经济性评估 [J]. 南方能源建设, 2020, 7(4): 67-74. DOI: 10.16516/j.gedi.issn2095-8676.2020.04.010. LU Z K, JIAN X H, ZHANG M H. Reliability and economy assessment of multi-terminal flexible DC distribution network [J]. Southern energy construction, 2020, 7(4): 67-74. DOI: 10.16516/j.gedi.issn2095-8676.2020.04.010.