| Based on the simulation tool of FASTEST and BPA, the transient stability margin of Suthern Cina Power Grid AC/DC hybrid system in 2005 and 2006 is analyzed and studied in this paper:(1) The dynamic characteristic of DC system while faults occur on rectifier terminal of AC system is studied. The model of DC control system is improved, and difference of dynamic characteristic of DC system is compared with that under orginal control model.(2) The influence of sequence and time of single-phase reclosing on transient stability margin in AC/DC Hybrid system in 2005 is studied when single-phase fault is occurred at both terminals of Anshun—Tianshengqiao 500kV transmission line in this paper. With the conclusion that when the terminal without fault uses non-voltage detecting and recloses first, the transient stability can be enhanced, a method combined with fault location algorithm to modify the sequence of single-phase reclosing online to enhance transient stability and lower the surge when reclose to permanent fault is proposed.(3) Influences on transient stability margin and HVDC system by using different HVDC modulation parameter under certain control modes, and by using the power slope of south AC transmission system and north AC transmission system as modulation singal and different modulation measures under different control modes, when fault is occurred on north AC transmission system in Southern China Power Grid in the year of 2005, with Guizhou-Guangdong HVDC system monopole operating and Tianshengqiao-Guangzhou HVDC system bipolar operating, is studied. Based on the simulation results, analysis of DC system modulation gain, singal and measure is done.(4) The influence of DC system modulation measure on transimission power of west-east cross-section is studied, when faults occur on AC system of west-east cross-section. Simulation indicates that it is not proper for Guizhou-Guangdong DC system to execute emergency power support while AC system faults occur near its recifier terminal.(5) The cross-section transient transmission limits of west-east and Yunnan power grid are simulated and analyzed in 2005 and 2006 year of Southern China Power Grid in this)paper. Influence of load model and changing mode on cross-section transmission limit is studied and analyzed. In this paper, the act of compensating capacitance including the limit of MOV and the time delay is considered. Simulation results indicate that transmission limit of cross-section without considering the act of compensating capacitance is on the high side. |
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