【作者】 姜莉；

【导师】 李卫星；

【作者基本信息】 哈尔滨工业大学 ， 电气工程， 2014， 硕士

【摘要】 近年来，人们越来越关注风能的开发利用，远离负荷中心的大规模集群式风电场不断出现。然而风电功率无法完全被本地消纳，需要对其进行集中的跨区域外送。基于模块化多电平换流器的多端直流输电（Multi-Terminal DirectCurrent based on Modular Multilevel Converter，MMC-MTDC）系统同时具备了MMC高电压、大容量的技术优势和MTDC系统灵活性、可靠性和经济性的运行特点，成为解决这一问题的最佳方案。因此，本文对MMC-MTDC系统的控制策略进行了研究，使其能更好地适应风电的随机性与间歇性。首先研究了MMC的基本工作原理。在忽略MMC各个子模块开关过程的基础上，建立了MMC的交直流解耦模型，将MMC等效为相互解耦的交流回路和直流回路两部分。在研究了MMC-HVDC控制系统基本构成的基础上，根据该模型，将换流站级控制系统分割为交流回路控制器、环流抑制控制器和阻尼控制器三部分，并设计了基于直接电流控制策略的负责调节MMC与交流系统之间功率交换的交流回路控制器。然后对MMC-MTDC系统的控制策略进行了研究。研究了多端柔性直流输电系统最为典型的主从控制、电压裕度控制和多点电压下降控制。通过对比分析，将它们归纳为单一主站型控制策略和多重主站型控制策略。考虑到直流电压控制和有功功功率控制的强耦合性，提出了复合主站型控制策略。该控制策略让控制直流电压的换流站专注于电压控制，调用其他换流站补偿系统的波动功率。这些换流站构成复合型的主站，共同承担传统主站的控制任务，提高了整个系统的直流电压质量。最后研究了含风电场的复合主站型MMC-MTDC系统。运用PSCAD/EMTDC搭建基于双馈异步发电机的风电机组模型，并应用等效参数法，对风电场进行了等值建模。在此基础上，搭建了采用复合主站型控制策略的含风电场的四端MMC-MTDC系统模型，在风速变化及各种故障状况下，对其运行特性进行了仿真研究。根据仿真结果，提出了相应的应对措施，以提高系统的稳定运行能力和经济性。更多还原

【Abstract】 At present, people have been focusing more on the development and utilizationof wind energy. Large-scale wind farms based on cluster mode which are far awayfrom the load centers continue to emerge. However, the wind power can’t becompletely consumed by the local load. It needs to be transmitted to anotherregional power grid by a centralized way. The best solution to this problem is themulti-terminal direct current system based on modular multilevel converter(MMC-MTDC system) with the advantages of both MMC and MTDC system. SinceMMC can withstand a high voltage and has a large capacity. MTDC system isflexible, reliable, and economical. Therefore, the control strategies of MMC-MTDCsystem are studied in this paper, so that it can better adapt to the randomness andintermittence of wind power.First, the basic principles of MMC are studied. Based on ignoring theswitching processes of sub-modules, the decoupled model between AC and DC sideof MMC is built. According to this model, the MMC is divided into AC-loop andDC-loop equivalently, both of which are decoupled from each other. The controllercomposition of MMC-HVDC is studied. According to the decoupled model betweenAC and DC side, the station-level controller is divided into AC-loop controller,circulating current suppressing controller and damping controller. Then, theAC-loop controller which is responsible for regulating the exchanged powerbetween MMC and AC system is designed based on the direct current control.Second, the control strategies of MMC-MTDC system are studied.Master-slave control, voltage margin control and multi-point DC voltage droopcontrol which are the most typical control strategies of MMC-MTDC system arestudied. Through comparative analysis, they are grouped into control strategies witha single master station and multiple master stations. Considering the DC voltagecontrol and active power control are strongly coupled, the control strategy withcompound master station is proposed. It makes the DC voltage converter stationfocus on the voltage control, and call other converter stations to compensatefluctuating power of the system. These converter stations constitute the compoundmaster stations, and share the control task of a traditional master station. Thiscontrol strategy can improve the DC voltage’s quality of the whole system.At last, the compound master station type MMC-MTDC system with windfarms is studied. By using PSCAD/EMTDC, a wind turbine model based on doublyfed induction generator is built. By using the equivalent parameter method, aequivalent wind farm model is built. Then, a four-terminal MMC-MTDC system model including wind farms using the control strategy with compound masterstation is built. Under wind speed changing and various fault conditions, theoperating characteristics of the system are simulated. According to the simulationresults, the corresponding measures are proposed to improve the stability of thesystem.更多还原