Power System Voltage Stability Assessment Considering Load Uncertainty

In recent years, many voltage collapse incidents have occurred at home and abroad successively, which cause great social disorders and huge economic losses.At the same time, with the rapid growth of the load demand, power system is closer and closer to the limit of stable operation, which makes the voltage stability problem became a hot spot to the researchers.This article dissertates the influence of the load uncertainty to the power system voltage stability. To assess the system voltage stability based on different analysis method.According to the analysis of static voltage stability of power system, the analysis method of power system voltage stability based on improved bisection searching technique is improved. Which is used to the Taiyuan 220kV actual system to identify the weak links of the system. And the calculated results are compared with the traditional continuous power flow method. The results show that the method based on improved bisection searching technique is correct and reliable. And the convergence of the algorithm is better than the traditional continuous power flow method.Focused on risk assessment of power system voltage stability under uncertainty, a method of power system voltage stability risk assessment used probabilistic load flow based on Latin hypercube sampling is proposed. A series of voltage stability risk assessment indices was proposed with consideration of the limit of load fluctuation. The probabilistic load flow based on Latin hypercube sampling, in combination with the N-1 fault analysis method, was applied to assess the voltage collapse states of power system caused by different load fluctuation. The distributions of load and node voltage at those states were analyzed and the corresponding distribution surfaces were drawn to show the possibility and seriousness of voltage collapse states of power system and the influence of load fluctuation on the node voltage. The proposed method was validated on IEEE 30 bus system and a practical 220kV Taiyuan power system in Shanxi Province, China. The simulation results show that the distributions of load, node voltage, total load under the states of system collapse can be found with the proposed method and the proposed indicators are correct, consistent and feasible in application.Aiming at the fuzzy uncertainty factors in power system voltage stability analysis, presents a method of voltage stability analysis based on fuzzy theory. Through establishment fuzzy mathematical model of voltage, use the Monte Carlo method based on adaptive principle to get the system state samplings, use the fuzzy entropy as the voltage quality of the system, to analysis system voltage stability. The proposed method was validated on IEEE 14 bus system. The simulation results show that the proposed method can identify the weak area of the system. Also can analysis the change of system crash ratio and average voltage with the load. Compared with the Monte Carlo simulation method, prove that the proposed method can improve the sampling efficiency.According to the proposed voltage stability assessment method, using MATLAB software to design the system voltage stability evaluation software considering load uncertainty.