Probabilistic Calculation of the Nearest Voltage Stability Critical Point

X.H. Zong, Y. Zhang, J.S. Zhang, and Z.G. Wu (PRC)


Voltage stability; Saddle node bifurcation; Probabilistic power flow; HVDC


The voltage stability margin is an important index for static voltage stability analysis in power systems. Since conventional methods of calculating the voltage stability critical point are based on a single system-operating condition the results obtained are optimistic. In this paper, a new method to determine the voltage stability critical point under a probabilistic environment is developed. The uncertainties considered are system multi-operating conditions derived from the operating profiles of nodal loads and generations. Making the assumption that these variables have a normal distribution the mean voltage stability margin and its standard variance can be found by iterating the continuation power flow (CPF) algorithm. The voltage stability margin lies within three standard deviations of the mean on either side with a probability very nearly equal to unity. This is of significance for power system dispatching operation. Because a range of operating conditions are considered results of this approach will be closer to practical circumstance than the results of deterministic methods. A thirteen-bus AC/DC parallel system illustrates the application of the proposed algorithm.

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