交直流混合系统电压稳定问题综述

Review on Voltage Stability of AC/DC Hybrid Grid

采用交直流输电已成为必然趋势,但高压直流输电(HVDC)也给系统带来了不良的负荷特性,使得换流站交流母线的电压稳定问题成为困扰直流输电系统正常运行的一个重要问题,特别在受端系统较弱时更是如此。为了寻找更好的方法来评价交直流系统电压稳定性,对交直流系统静态电压稳定性分析方法进行归纳,评价了它们的优缺点,提出从交直流系统潮流计算方法和电压崩溃点计算方法两方面来改进分析方法。在交直流系统动态电压稳定性分析中,对建模的现状和存在的问题以及动态负荷对电压稳定的影响方面进行了描述,明确了建模要考虑动态负荷,既能描述换流器换相失败的动态特性,又要能用于求解大规模交直流系统。最后从交流系统和直流系统两方面讨论了防止电压失稳的措施。

The application of AC/DC hybrid grid has become an obvious trend in power transformation. High voltage DC transformation (HVDC), however, often brings forth poor load characteristics of power systems. Particularly, the voltage of converter buses tends to be unstable. This causes a problem which affects the normal operation of HVDC. This problem becomes more serious when the system on the receiving side is weak. Aiming at finding a better method to evaluate voltage stability of AC/DC system, this paper reviews the existing methods of static voltage stability analysis in AC/DC systems. It suggests some changes to algorithms for the computation of power flow and the voltage point when the collapse occurs. This paper also describes the existing problems of modeling of AC/DC systems and the influence of dynamic loads on voltage stability. It has been shown clearly that modeling of the AC/DC hybrid grids should take into account the dynamic loads and it can not only describe dynamic characteristics of converters when they suffer commutation failure, but also be applicable to analysis of large-scale AC/DC systems. This paper finally discusses some ways of preventing the voltage of both AC and DC systems from being unstable.