MMC-MTDC系统的主从控制策略研究

发布时间：2018-12-24 13:22

【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。
[Abstract]:In recent years, people pay more and more attention to the development and utilization of wind energy. However, the wind power can not be completely absorbed locally, and it needs to be centralized transregional delivery. Multiterminal direct current transmission (Multi-Terminal DirectCurrent based on Modular Multilevel Converter,MMC-MTDC) system based on modularized multilevel converter has the advantages of high voltage and large capacity of MMC, flexibility, reliability and economy of MTDC system. Be the best solution to this problem. Therefore, the control strategy of MMC-MTDC system is studied in this paper, so that it can adapt to the randomness and intermittency of wind power better. Firstly, the basic principle of MMC is studied. On the basis of ignoring the switching process of each sub-module of MMC, the AC / DC decoupling model of MMC is established. The MMC is equivalent to two parts of AC and DC circuits which are decoupled from each other. On the basis of studying the basic structure of MMC-HVDC control system, according to the model, the converter station control system is divided into three parts: ac loop controller, circulation suppression controller and damping controller. The AC loop controller which regulates the power exchange between MMC and AC system is designed based on direct current control strategy. Then the control strategy of MMC-MTDC system is studied. The most typical master-slave control, voltage margin control and multi-point voltage drop control for multi-terminal flexible direct current transmission system are studied. Through comparison and analysis, they are classified as single master station control strategy and multiple master station control strategy. Considering the strong coupling between DC voltage control and power control, a compound master station control strategy is proposed. The control strategy makes the converter which controls DC voltage focus on voltage control and calls other converter stations to compensate for the fluctuating power of the system. These converter stations constitute complex master stations, which jointly undertake the control tasks of traditional main stations and improve the DC voltage quality of the whole system. Finally, the composite master station MMC-MTDC system with wind farm is studied. The wind turbine model based on doubly-fed asynchronous generator is built by using PSCAD/EMTDC, and the equivalent modeling of wind farm is carried out by using equivalent parameter method. On this basis, a four-terminal MMC-MTDC system model with a composite master station control strategy is built, and its operation characteristics are simulated under the wind speed variation and various fault conditions. According to the simulation results, the corresponding countermeasures are put forward to improve the stability and economy of the system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM721.1

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