小水电富集电网的柔性直流异步联网方案研究

Study on VSC-HVDC Asynchronous Interconnection Schemes for Regional Grids Containing Large-Scale Small Hydropower

云南西部大规模小水电群集中送出地区存在弱阻尼区间振荡模式，是制约该地区电力送出的主要因素。为避免大规模小水电群引发全网的弱阻尼振荡。可通过柔性直流输电系统将小水电富集电网和主网进行异步联网，使参与因子最大的机群与主网机群形成电气隔离。以云南电网为背景，从经济性和降低直流系统故障概率的角度，设计了柔性直流背靠背异步联网方案；从优化小水电富集电网潮流分布的角度，设计了多端柔性直流异步联网方案。比较了2种方案对电网小扰动稳定性和小水电富集电网送出能力的提升效果。仿真结果表明：2种方案均可增强云南电网的小扰动稳定性，并有效提升小水电富集电网的送出能力。

There existing a weak damping oscillation mode in the western Yunnan province, where the power of the large-scale small hydropower are delivered in concentration. And this is the major constraint that limits the transmission capacity of this area. To avoid the large-scale small hydropower triggering the weak damping oscillations of the whole grid, we can use VSC-HVDC systems to connect the small-hydropower concentrated grids to the backbone grid asynchronously, which will electrically isolates the machine groups of the largest participation factor from the machine groups of the backbone grid. This paper designed a VSC- HVDC back-to-back asynchronous interconnection scheme from the perspective of economy and reducing the probability of DC system faults. Besides, from the perspective of optimizing power flow distribution of the small-hydropower concentrated grids, a VSC-MTDC asynchronous interconnection scheme was designed. Effects of the two schemes on the system small-signal stability and the transmission capacity of the small-hydropower concentrated grids were compared. The simulation results show that both the two schemes can enhance the small-signal stability of Yunnan grid and increase the transmission capacity of the small-hydropower concentrated grids effectively.