大扰动下的交直流相互影响特性及其控制策略研究

The strong interaction between AC and DC systems threatens the safe and stable operation of the multi-infeed hybrid AC/DC power grid. The study on this subeject has great theoretical value and realistic significance. A further study on the AC/DC system interaction and its control strategy under large disturbance in such power grids will be carried out in this project. Firstly, a quantitative measurement index for real-time on-line assessment of AC/DC system interaction based on the Wide Area Measurement System (WAMS) will be proposed. Then, according to the on-line assessment index, a coordinated recovery strategy for multiple DC transmission systems to relieve rapidly the unbalance of system active power after the occurrence of faults will be put forward, in which the Voltage Dependent Current Order Limiter (VDCOL) and reative power control in converter stations are utilized at the same time. Finally, the role of dynamic reactive power compensation to the voltage of AC corridors and inverter-side AC system during the fault recovery phase will be studied. The arrangement principles of Static Var Compensators or Static Synchronous Compensators (SVCs or STATCOMs) will be determined by a method combining linearization with nonlinearization. Relative Gain Array (RGA)will be used to select SVC/STATCOM input signals. The pole placement and some optimzation algorithm will be utilized to design and coordinate the control parameters of the SVCs/STATCOMs. The research results will lay a theoretical foundation and provide references for the safe and stable operation of such systems both at home and abroad.

交直流系统间复杂的相互影响给多馈入混联电网的安全稳定运行带来威胁，对其进行深入研究具有重要的理论价值和现实意义。本项目拟对大扰动下的交直流相互影响特性及其控制策略进行研究。首先，基于广域测量系统（WAMS）提出一种能够实时在线评估交直流相互影响特性的量化指标；继而，基于该评估指标提出一种换流站无功控制功能和低压限流(VDCOL)功能相结合的多HVDC故障恢复策略，以缓解故障后送受端交流系统有功功率的不平衡；最后，研究动态无功补偿对交流通道和受端交流系统动态电压的支撑作用，主要内容包括：（1）采用线性化和非线性化相结合的方法来确定动态无功补偿装置的布点方案；（2）基于相对增益矩阵（RGA）方法为动态无功补偿装置控制器选取最优的反馈信号；（3）利用极点配置方法及相应的优化算法来设计和协调无功补偿控制器的参数。研究成果将为该类电网的安全稳定运行奠定理论基础，也可为国内外类似电网提供参考。

高压直流采用共站同塔双回架设的设计思路，可以合理高效地利用接地极和换流站的资源，提高单位走廊的输送容量，降低工程建设和维护费用。对于共换流站、线路杆塔、接地极和交流场的同塔双回直流输电系统，双回直流功率的协调控制以及换流站无功功率的统一控制使得该类直流工程的控制系统更加复杂。本研究对共站同塔双回直流输电系统的控制策略进行了深入研究。提出了一种双回直流功率的协调控制策略，在输送相同有功功率的前提下，该策略不仅使换流站无功交换量更少，同时也减小了接地极电流；研究了一种以直流电压为控制量，以交直流系统无功交换量作为反馈量的“开环+闭环”无功控制方法，开环控制可以保证换流站与交流系统交换无功功率的快速控制，闭环控制可以保证交流系统交换无功功率的稳态精度。研究成果将为该类直流输电工程的安全稳定运行奠定理论基础，也可为后续的同类型工程的设计工作提供一定的指导和借鉴意义。