A semi-dynamic approach to the voltage stability analysis of interconnected power networks with random loads

In planning an interconnected power network it is very important to assess whether a voltage collapse occurs during a prefixed operating condition. However, the realistic circumstance, due to load forecast, that the nature of loads can be non-deterministic makes the use of present deterministic procedures unreliable, particularly when the network is operating near its voltage stability limit. To overcome this difficulty, the paper presents a practical probabilistic approach which treats loads as correlated random variables with multivariate normal distribution. Starting with a suitable linearized model of the system, the suggested technique can quantify the proximity of a power network to voltage instability under various expected operating conditions and, accordingly, can identify systematically all critical load buses. The usefulness and capability of the approach are illustrated by a numerical example.