Study on Multi-infeed AC and DC Hybrid Power System Security and Stability

摘要

By 2015, several ultra-large-scale multi-infeed AC and DC hybrid power systems will be formed in China. Comparing with pure AC transmission system and Single-infeed HVDC system, multi-infeed DC power system will increase the complexity of system structure while increase flexibility of system operation mode and power sources arrangement as well as expand transmission capacity. In the multiinfeed AC and DC hybrid power systems, since AC and DC transmission lines are in parallel operation and the electrical distances between many DC converters are very short, there will be interactions between AC and DC systems and between DC subsystems, which will put forward new challenges to the operating characteristics analysis and stability control strategy of multi-infeed AC and DC hybrid systems. This paper starts from discussing complicated interactions between AC and DC systems and interactions between DC systems in the multi-infeed DC transmission system, outlining the studies on researches of commutation failure of multi-infeed AC and DC power system, DC system failure recovery, the power angle/voltage stability problems, and etc. Then, it proposes two indicators, namely Multi-infeed Short Circuit Ratio and Multi-infeed Interaction Factor, to measure the interaction extent between the AC systems and its connected DC systems. In the end, the paper takes the grid structure of North China power grid planned for 2015 as an example, using PSD-BPA simulation program, to conduct simulation and analysis for following failure situations respectively, such as DC system commutation failures caused by other unipolar/bipolar DC block, major AC channel failure, and AC receiving system failure.