Difference analysis of AC tie-line power fluctuation caused by different DC blocking for two-area interconnected power systems

Different DC blocking even in the same region will cause different peak values of AC tie-line active power fluctuation. The reason that lead to this phenomenon is discussed in this paper based on the hybrid UHV AC/DC system for North China and Central China interconnected power grid. By deducing time-domain equation of tie-line power is deduced on two-machine equivalent system, the maximum power oscillation equation is modified considering the impact of electromagnetic mutation. It's pointed out that the farther the distance between DC fault and AC tie-line is, the smaller the electromagnetic mutation is, and the greater the peak value of the tie-line fluctuation is. Then the conclusions are respectively verified by using both two-machine four-DC equivalent system and the North China and Central China interconnected power system.