含风电并网的柔性直流输电控制策略研究

发布时间：2019-03-19 12:35

【摘要】：随着世界各国对能源安全、生态环境、气候变化等问题日益重视,加快风电等可再生能源的发展已成为国际社会为推动能源转型、应对气候变暖的普遍共识和一致行动。但由于风电等可再生资源的波动性、随机性、地域发展不平衡等特点,导致消纳问题日渐严重。基于电压源换流器和全控性器件的柔性直流输电具有功率灵活可控、电能质量好、无换相失败等优势,逐渐成为了解决风电特别是海上风电接入的最有效的方式。不仅如此,柔性直流输电技术在弱电网供电、城市扩容以及电力市场方面均发挥着无可替代的优势,已然成为了我国智能电网建设的重要环节。本文主要对柔性直流输电系统的控制策略进行了研究。首先,分析了柔性直流输电技术运行原理以及具有快速电流响应特性和有功、无功功率解耦控制等优点的电压外环和电流内环的双环控制策略;然后,对柔性直流输电系统主从控制、电压裕度控制和直流电压下垂控制的控制原理及特点进行详细的介绍,并在此基础上,提出了一种协调控制策略,该策略综合三种控制方式分层协调各换流站,能够适应较大范围的不平衡功率,避免换流站过载的现象;之后,研究了风电并网的控制策略,受端换流站采用适合潮流频繁变动的直流电压下垂控制方式,可以实现功率的连续控制,但直流电压会产生明显的偏差,为了改善此问题,提出了一种改进的直流电压下垂控制策略,该策略在直流电压参考值的基础上叠加了一补偿项,抵消了直流电压因功率变化导致的电压偏差,从而实现了直流电压的无差调节;最后,在Matlab/simulink平台上构建了多端柔性直流输电模型,分别仿真验证了所提控制策略的有效性。
[Abstract]:With the increasing attention to energy security, ecological environment, climate change and other issues in the world, accelerating the development of renewable energy such as wind power has become the universal consensus and concerted action of the international community in order to promote the transformation of energy and deal with climate warming. However, due to the volatility, randomness and unbalanced regional development of wind power and other renewable resources, the problem of consumption is becoming more and more serious. Flexible DC transmission based on voltage source converter and fully controlled devices has the advantages of flexible power control, good power quality and no commutation failure, which has become the most effective way to solve the problem of wind power, especially offshore wind power access. In addition, flexible DC transmission technology plays an irreplaceable advantage in weak grid power supply, urban expansion and power market, and has become an important link in the construction of smart grid in China. In this paper, the control strategy of flexible HVDC transmission system is studied. Firstly, the operation principle of flexible DC transmission technology and the double-loop control strategy of voltage outer loop and current inner loop with the advantages of fast current response, active power decoupling control and reactive power decoupling control are analyzed. Then, the control principles and characteristics of master-slave control, voltage margin control and DC voltage droop control of flexible HVDC transmission system are introduced in detail, and on this basis, a coordinated control strategy is proposed. The strategy integrates three control modes to coordinate each converter station and can adapt to a wide range of unbalanced power and avoid the phenomenon of overload of converter station. After that, the control strategy of wind power grid connection is studied. In order to improve this problem, the terminal converter station adopts the DC voltage droop control mode which is suitable for frequent change of power flow, which can realize the continuous control of power, but the DC voltage will produce obvious deviation. In this paper, an improved DC voltage droop control strategy is proposed. Based on the DC voltage reference value, a compensation term is added, which offsets the voltage deviation caused by the change of DC voltage, and thus realizes the no-difference regulation of DC voltage. Finally, a multi-terminal flexible HVDC transmission model is constructed on the Matlab/simulink platform, and the effectiveness of the proposed control strategy is verified by simulation.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1

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