计及并联电容器补偿的多馈入交直流系统改进有效短路比指标

多馈入有效短路比能够同时反映交流系统强弱和直流系统间相互作用，是进行多馈入交直流系统分析和评估的重要指标，但是在实际工程应用中仍出现了指标计算结果与系统实际电压稳定不相符的情况。在推导并联电容器补偿对短路电流影响的数学关系的基础上，分析得出现有的多馈入有效短路比指标由于未考虑并联电容器补偿时存在不足而具有局限性。针对这个问题，提出一种能够计及并联电容器补偿的改进多馈入有效短路比指标，该指标通过将系统并联电容器容量折算到直流落点处来进一步计及其给系统电压稳定带来的影响，并给出所提改进短路比指标的计算公式。以修改的新英格兰39节点系统为例，研究了并联电容器补偿对系统电压稳定性的影响，分析了现有多馈入短路比和所提改进指标与并联电容器补偿的容量和补偿位置的关系，研究结果表明，所提改进有效短路比指标比现有多馈入有效短路指标更能够准确地反映交流系统的强弱程度。最后通过浙江电网仿真验证了所提改进有效短路比在描述多馈入交直流系统强度的准确性和适用性。

An improved effective short circuit ratio of multi-infeed AC/DC power system considering shunt capacitors

Multi-infeed effective short-circuit ratio (MESCR), which can reflect strength of the AC system as well as the influence of DC systems interaction, is an important index for analysis and evaluation of multi-infeed AC/DC power system. This paper theoretically proves the limitation of the existing MESCR on evaluating the influence of massive shunt capacitor compensation, and then proposes an improved multi-infeed effective short circuit ratio (IMESCR) to take the impact of the shunt capacitors into account by converting the capacity of shunt capacitors to inverter station of HVDC. Case study is carried out based on New England 39-bus system to analyze the influence of capacity and location of the shunt capacitors on MESCR and IMESCR, respectively. The simulation results indicate that the proposed IMESCR is able to describe the strength of AC/DC power system more accurately than MESCR. Finally, the feasibility and accuracy of the proposed IMESCR are validated through simulation study of Zhejiang power grid. This work is supported by National Key Research and Development Program of China (No. 2016YFB0900805).