MMC-HVDC系统的启停控制策略研究

发布时间：2018-05-02 02:35

本文选题：模块化多电平换流器（MMC） + 启停控制　；参考：《华南理工大学》2014年硕士论文

【摘要】：德国西门子公司采用模块化多电平换流器的海湾柔性直流输电工程（Trans BayCable Project）已于2010年正式投运，各国也相继拟建成MMC-HVDC工程，对MMC-HVDC的研究具有重要的实际应用价值。合适的换流站启动控制策略对缓解MMC-HVDC系统启动过程中对自身和交流电网的冲击影响非常重要，若只采用稳态运行时的控制策略而不采取其他辅助措施，将会产生严重的过电压和过电流现象，甚至导致系统振荡，影响交流系统正常运行，危及设备安全，因此对该过程进行研究具有重要意义。为确保桥臂子模块电容电压稳定，避免MMC换流器因为少量子模块发生故障而停机检修，本文给出了三种可行的冗余保护方案，并通过Matlab/Simulink仿真分析，选择了适合MMC的最佳冗余保护方案。根据换流站两端所连接电网的不同形式，将换流站的启动方法分为有源方式和无源方式。对于有源启动方式，提出一种解锁方案用于减小对端换流站解锁时对直流和交流电网的电流冲击影响。对于无源启动方式，在逆变站空载启动并网前，提出一种逆变侧直接电压控制器，并且针对由于逆变站子模块充电不足导致可控解锁逆变站时产生过大的电流冲击这一问题，，提出了逆变站的两种辅助充电策略。另外，针对无源启动时逆变站侧电网接入形式的不同，提出了并网后切换逆变侧控制策略的方案，并验证了上述所提策略的正确性和有效性。最后，将整个停机过程分为能量反馈阶段和电阻能耗阶段。同时，为使逆变站子模块能最大限度地将能量反馈回电网，在换流站向无源网络供电时，提出逆变侧换流站采取改变每相投入模块数的低压放电解锁策略。另外，在能耗阶段，采用一定的辅助触发策略使各子模块剩余能量以电阻发热的形式逐步耗散掉，并仿真验证了整个停机过程的有效性。
[Abstract]:Trans BayCable Project, a Gulf flexible direct current transmission project with modular multilevel converters, has been formally put into operation in 2010, and many countries are planning to build MMC-HVDC project one after another, which has important practical application value for the study of MMC-HVDC. The appropriate startup control strategy of converter station is very important to mitigate the impact of MMC-HVDC system startup on itself and AC power grid. If only the control strategy of steady operation is adopted and no other auxiliary measures are taken. It will cause serious overvoltage and overcurrent phenomenon, even lead to system oscillation, affect the normal operation of AC system, endanger the safety of equipment, so it is of great significance to study this process. In order to ensure the capacitance voltage stability of the submodule of the bridge arm, and to avoid the MMC converter from stopping and overhauling because of the failure of a few sub-modules, three feasible redundant protection schemes are presented in this paper, and analyzed by Matlab/Simulink simulation. The optimal redundancy protection scheme suitable for MMC is selected. According to the different forms of power grid connected at both ends of converter station, the starting method of converter station is divided into active mode and passive mode. For active start-up, an unlocking scheme is proposed to reduce the impact of current impact on DC and AC power grids when the terminal converter station is unlocked. For passive startup mode, a direct voltage controller of inverter side is proposed before the inverter station starts up and connected to the grid without load. The problem of excessive current impact caused by insufficient charging of the submodule of the inverter station leading to the controllable unlocking of the inverter station is pointed out. Two auxiliary charging strategies for inverter station are proposed. In addition, the scheme of switching inverter side control strategy after grid connection is put forward, and the correctness and effectiveness of the above strategy are verified in view of the different access forms of inverter station side power network during passive start-up. Finally, the whole shutdown process is divided into energy feedback stage and resistance energy consumption stage. At the same time, in order to maximize the energy feedback of the inverter station submodule, when the converter station supplies power to the passive network, the inverter side converter station adopts a low-voltage discharge unlocking strategy to change the number of input modules per phase. In addition, in the energy consumption stage, the residual energy of each sub-module is dissipated gradually in the form of resistance heating by a certain auxiliary trigger strategy, and the effectiveness of the whole shutdown process is verified by simulation.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM721.1

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