On-Line Voltage Stability and Transient Stability Assessment

9419458吉吉斯：本研究的主要目标是开发在线电压稳定和暂态稳定的新方法。负荷预测和电压相量、发电机频率偏差及其变化率的最优估计将是发展的基本信息。在此基础上，建立了静态指标和暂态指标，分别用于电压失稳预测和暂态稳定检测。在正常运行条件下，计算了静态电压失稳指标，并对其未来值进行了预测。一旦系统进入暂态，将计算用于检测暂态不稳定性的暂态指数。潮流解被认为是空间和空间曲线的交点。运行点处空间曲面的梯度向量与空间曲线的切向向量之间的夹角可视为电压失稳的静态指标。它接近90度可能表示工作点与电压崩溃点的接近程度。空间曲面方程中母线注入功率在空间曲线切线向量方向上的方向导数可能是弱母线识别的候选方向。所提出的指标适用于电压相量和潮流雅可比。为了预测电压不稳定，可以根据未来负荷及其相应的潮流解来计算电压不稳定指数。通过比较当前运行状态的电压不稳定指标和预测负荷的电压不稳定指标，可以得出系统是否会接近或远离电压崩溃点的结论。如果系统处于暂态，则初步检测到不稳定模式。在此基础上，提出了扰动后阶段的发电机角度预测差。一旦预测出不稳定模式，高维电力系统模型就可以聚合成低阶模型。提出了将该聚合低阶系统的动能作为暂态稳定检测的暂态指标。***

9419458 Girgis The mail objectives of this research are to develop new methods for on-line voltage stability and transient stability. Load forecasting and the optimal estimation of voltage phasors, generator frequency deviations, and their rate of change will be the basic information for the development. Based on these values, a static index and a transient index will be developed for voltage instability prediction and transient stability detection, respectively. During normal operating conditions, the static index for voltage instability is calculated, and its future values are predicted. Once the system enters a transient state, the transient index, which is for transient instability detection, will be computed. Load flow solutions are considered as the intersections between a space and a space curve. The angle, between the gradient vector of a space surface and the tangent vector of a space curve at an operating point, may be considered as the static index for voltage instability. Its closeness to 90 degrees may indicate the proximity of the operating point to the voltage collapse point. The directional derivatives of the bus injection power in the space surface equation, in the direction of the tangent vectors of the space curves, are possible candidates for weak bus identifications. The proposed indices are available for the voltage phasors and the load flow Jacobian. To predict voltage instability, the voltage instability index may be computed based on the future load and its corresponding load flow solutions. By comparing the voltage instability index for the current operating condition with the index for the predicted load, one may conclude if the system will become close to or away from the voltage collapse point. If the system is in transient state, the unstable mode will be detected primarily. The predicted generator angle difference in the post disturbance period is proposed for this purpose. Once the unstable mode is pred icted, the high dimensional power system model may be aggregated into a low order model. The kinetic energy of this aggregated low order system is proposed as the transient index for transient in stability detection. ***