As power system interconnection between utilities increased, the traditional method of frequency dynamics analysis based on the single-machine model no longer adapted to the modern power system. A method for frequency dynamics analysis and load shedding assessment is proposed in this paper, which maps the simulation trajectories in the multi-machine space to a single-machine space by using the center-of-inertia transform. This method not only takes advantage of numerical integral method, which is not limited by the model, but also uses the concept of uniform frequency of the single-machine model to compensates the shortage of numerical integral method effectively. The influences of different network structures, and operation modes on the frequency dynamics are analyzed. A new under frequency load shedding (UFLS) scheme is proposed which can not only meet the frequency security requirements of the entire network but also the one of the regional network. Finally, lots of simulation results are compared with the traditional scheme and show that the new method has much more adaptability.%随着电网互联的发展,传统的单机带集中负荷模型已经不能适应现代电网频率动态特性分析的要求.本文提出了一种将多机系统仿真轨迹通过惯量中心变换映射到单机系统上进行频率动态分析的方法.该方法既发挥了数值积分方法可以提供任意复杂模型的准确时域解的优势,又可以利用单机模型中成熟的理论和相应参数进行定量分析.应用上述方法研究了广东电网频率动态特性,分析了不同地区电网结构差异性,不同时间的运行方式差异性对频率动态特性的影响,提出了既适应全网频率特性要求又考虑地区电网频率差异的低频减载方案.最后,对上述传统方案和优化后方案进行仿真对比,结果证明了该方法的优越性.
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