This paper proposes a novel method of identifying buses vulnerable to power system voltage instability. Unlike traditional sensitivity and modal analysis methods, the proposed method can preserve the nonlinearity of power flow equations, and visually pinpoint the vulnerable buses in advance for any possible load increasing scenarios. Based on the power flow equations on decomposed two-bus equivalent channels from the power network, a vulnerability index is introduced and visualized for each channel in the solvability region of its decoupled power flow equations bounded by a parabola. It is found that the arrival at the parabolic boundary indicates a potentially vulnerable bus but not necessarily results in voltage collapse. Thus, a criterion on the gradient of vulnerability index trajectory is proposed to discover and differentiate two types of potentially vulnerable buses: one type has trajectories that are tangent to the boundary but stay inside the solvability region; the other type has trajectories crossing the boundary to result in unsolvable power flow equations, which are identified as the vulnerable buses. The proposed method is validated on the IEEE 14-bus, IEEE 118-bus, and New England power systems with comparison to the traditional methods, and the test results show that the proposed method performs better than the traditional methods with satisfactory robustness under voltage fluctuation. In particular, the proposed method is 33.3% and 66.7% more accurate than the voltage sensitivity method in prospective operating conditions on the IEEE 14-bus and 118-bus systems, respectively.

本文提出了一种识别易受电力系统电压不稳定影响的总线的新方法。与传统的灵敏度和模态分析方法不同，所提出的方法可以保留潮流方程的非线性，并针对任何可能的负载增加场景提前直观地确定易受攻击的母线。基于来自电网的分解的双母线等效通道上的潮流方程，在其解耦潮流方程的可解性区域中引入并可视化每个通道的脆弱性指数，该指数由抛物线界定。发现到达抛物线边界表明存在潜在的易受攻击的总线，但不一定会导致电压崩溃。因此，提出了脆弱性指数轨迹梯度的准则，以发现和区分两类潜在的脆弱总线：一类具有与边界相切但留在可解区域内的轨迹；另一种类型具有跨越边界的轨迹，导致无法求解的潮流方程，这些方程被识别为易受攻击的总线。与传统方法相比，该方法在IEEE 14总线、IEEE 118总线和新英格兰电力系统上进行了验证，测试结果表明该方法优于传统方法，在电压波动下具有令人满意的鲁棒性. 特别是，所提出的方法是 33.3% 和 66。