送受端系统短路比关系对直流输电系统最大输送功率的影响

针对直流输电送端系统的运行状况是否对输送功率有影响的问题展开分析,研究了交直流系统整流侧联于不同强度交流系统的运行特性,结合逆变侧联于不同强度交流系统的运行情况,指出送端系统短路比与受端系统短路比的大小关系会影响直流输电系统可输送的最大功率。首先研究了整流站和逆变站的功率曲线,分别得到送受端系统短路比与其相应的最大输送功率的定量关系。然后分析了在相同的输送功率极限下整流侧和逆变侧短路比的关系,将两端系统可输送的最大功率相等时的短路比定义为转折短路比,并得到输送功率转折点。最后指出送受端系统的强度都会影响直流输电系统的输送能力,当两端系统短路比与转折短路比存在某种关系时,由其中的一端系统对直流系统的输送能力起决定性作用,并通过PSCAD仿真验证了结论的正确性。

Effect of the Ratio of Rectifier and Inverter SCR on Maximum Transmission Power of HVDC System

As to the influence of the operation status of sending system on transmission power, the operation characteristics of the HVDC rectifier connecting to various strength AC systems are studied. By combining with operation status of the inverter that connect to various strength AC systems, it is pointed out that the size relation of rectifier and inverter SCR (short circuit ratio)can affect maximum transmission power of HVDC system. Firstly, according to power curves of rectifier and inverter, the quantitative relationships between maximum transmission power and SCR are achieved respectively. Through comparing rectifier and inverter SCR under the same maximum transmission power condition, the turning point of SCR (TSCR)is defined as that obtained when maximum transmission powers of two terminal systems are equal. Finally, it is pointed out that the SCR of both inverter and rectifier sides would affect the transmission capacity. When there is certain relationship between rectifier and inverter SCR with TSCR, the transmission capacity of HVDC system is limited by one terminal side. Simulation results in PSCAD show the correctness of phenomenon founding.