柔性直流电网直流过电压分析及控制策略研究
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摘要
基于MMC的运行基本原理,研究了柔直电网功率不平衡时桥臂电容的充电过程,得到了直流电压与不平衡功率之间的表达式。针对不平衡功率引起的直流过电压问题,现有的故障穿越措施主要有紧急降低风电功率和装设耗能装置2种,该文提出了一种自适应NLM策略实现直流电压的紧急控制,可延长直流电压上升达到保护定值的时间,在换流站闭锁前实现安控有效切机。通过在PSCAD/EMTDC中搭建电磁暂态模型进行仿真分析,验证了该策略的有效性。
Based on basic operation principle of modular multi-level converter(MMC), charging process of bridge arm capacitor with unbalanced power in MMC-HVDC grid is studied, and the expression of relationship between DC voltage and unbalanced power is obtained. Existing fault-ride-through strategies mainly include emergency reduction of wind power and additional installation of energy dissipation devices. This paper proposes an improved emergency modulation strategy to suppress DC overvoltage by adjusting input numbers of sub-module adaptively. This strategy can reserve sufficient time to cut the unbalanced power and achieve fault-ride-through. An electromagnetic transient model is built in PSCAD/EMTDC, and effectiveness of the strategy is verified with simulation.
Based on basic operation principle of modular multi-level converter(MMC), charging process of bridge arm capacitor with unbalanced power in MMC-HVDC grid is studied, and the expression of relationship between DC voltage and unbalanced power is obtained. Existing fault-ride-through strategies mainly include emergency reduction of wind power and additional installation of energy dissipation devices. This paper proposes an improved emergency modulation strategy to suppress DC overvoltage by adjusting input numbers of sub-module adaptively. This strategy can reserve sufficient time to cut the unbalanced power and achieve fault-ride-through. An electromagnetic transient model is built in PSCAD/EMTDC, and effectiveness of the strategy is verified with simulation.
引文
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[16]王姗姗,周孝信,汤广福,等.模块化多电平换流器HVDC直流双极短路子模块过电流分析[J].中国电机工程学报,2011,31(1):1-7.Wang Shanshan,Zhou Xiaoxin,Tang Guangfu,et al.Analysis of submodule overcurrent caused by DC pole-to-pole fault in modular multilevel converter HVDC system[J].Proceedings of the CSEE,2011,31(1):1-7(in Chinese).
[2]Lesnicar A,Marquardt R.An innovative modular multilevel converter topology suitable for a wide power range[C]//2003 IEEE Bologna Power Tech Conference Proceedings.Bologna,Italy:IEEE,2003.
[3]Moradzadeh M,Shayeghi H,Vandevelde L,et al.Impact of increased penetration of large-scale wind farms on power system dynamic stability-A review[C]//International Conference on Environment and Electrical Engineering.Rome,Italy:IEEE,2015:1522-1526.
[4]CIGRE B4-52 Working Group.HVDC Grid Feasibility Study[R].Melbourne:International Council on Large Electric Systems,2011.
[5]孙文博,徐华利,付媛,等.应用于大型风电基地功率外送的多端直流输电系统协调控制[J].电网技术,2013,37(6):1596-1601.Sun Wenbo,Xu Huali,Fu Yuan,et al.Coordinated control of multi-terminal DC transmission system to send out power from large-scale wind farm[J].Power System Technology,2013,37(6):1596-1601(in Chinese).
[6]Adeuyi O D,Cheah-Mane M,Liang J,et al.Preventing DCover-voltage in multi-terminal HVDC transmission[J].CSEE Journal of Power&Energy Systems,2015,1(1):86-94.
[7]Feltes C,Wrede H,Koch F W,et al.Enhanced fault ride-through method for wind farms connected to the grid through VSC-based HVDC transmission[J].IEEE Transactions on Power Systems,2009,24(3):1537-1546.
[8]孙世贤,田杰.提升直流并网风电故障穿越能力的新方法[J].电力自动化设备,2013,33(8):137-141.Sun Shixian,Tian Jie.Enhancement of fault ride-through capability for grid-connected wind farm[J].Electric Power Automation Equipment,2013,33(8):137-141(in Chinese).
[9]Vidal-Albalate R,Beltran H,Rolán A,et al.Analysis of the performance of MMC under fault conditions in HVDC-based offshore wind farms[J].IEEE Transactions on Power Delivery,2016,31(2):839-847.
[10]Tzelepis D,Rousis A O,Dy?ko A,et al.Enhanced DC voltage control strategy for fault management of a VSC-HVDC connected offshore wind farm[C]//IET International Conference on Renewable Power Generation.London,UK:IET,2017.
[11]厉璇,宋强,刘文华,等.风电场柔性直流输电的故障穿越方法对风电机组的影响[J].电力系统自动化,2015(11).Li Xuan,Song Qiang,Liu Wenhua,et al.Impact of fault ride-through methods on wind power generators in a VSC-HVDC system[J].Automation of Electric Power Systems,2015,39(11):31-36(in Chinese).
[12]常非,王一,王一振,等.基于模块化多电平变换器的高压直流输电故障特性与控制保护[J].高电压技术,2015,41(7):2428-2434.Chang Fei,Wang Yi,Wang Yizhen,et al.Faults feature analysis and control protection strategies of modular multilevel converter based high voltage direct current[J].High Voltage Engineering,2015,41(7):2428-2434(in Chinese).
[13]李琦,宋强,刘文华,等.基于柔性直流输电的风电场并网故障穿越协调控制策略[J].电网技术,2014,38(7):1739-1745.Li Qi,Song Qiang,Liu Wenhua,et al.A coordinated control strategy for fault ride-through of wind farm integration based on VSC-HVDC[J].Power System Technology,2014,38(7):1739-1745(in Chinese).
[14]Silva B,Moreira C L,Leite H.Control strategies for AC fault ride through in multiterminal HVDC grids[J].IEEE Transactions on Power Delivery,2014,29(1):395-405.
[15]王铁柱,卜广全,王姗姗,等.一种提高MMC交流电压鲁棒性的改进调制策略[J].电网技术,2018,42(3):797-803..Wang Tiezhu,Bu Guangquan,Wang Shanshan,et al.An improved modulation strategy for improving the robustness of MMC ACvoltage[J].Power System Technology,2018,42(3):797-803(in Chinese).
[16]王姗姗,周孝信,汤广福,等.模块化多电平换流器HVDC直流双极短路子模块过电流分析[J].中国电机工程学报,2011,31(1):1-7.Wang Shanshan,Zhou Xiaoxin,Tang Guangfu,et al.Analysis of submodule overcurrent caused by DC pole-to-pole fault in modular multilevel converter HVDC system[J].Proceedings of the CSEE,2011,31(1):1-7(in Chinese).