A three-layer severity index for power system voltage stability assessment using time-series from dynamic simulations

This paper presents a three-layer voltage stability index computed using time-series obtained from dynamic simulations. The proposed index provides the distance with respect to voltage and power limits. Voltage, active and reactive power signals, which are determined using time series from dynamic simulations, are used to compute the index. The methodology assumes that no other information about the system (model) is available. A set of 3 different simulations at different loading levels and a given contingency are required to calculate the index. In the first layer, a two-element vector indicates if a power or a voltage limit was violated. In the second layer, a vector is used to specify which power and voltage loading level was violated and finally, in the third layer a matrix is used to retrieve precise information about which power and voltage limit has been violated in pre- or post-contingency. The index can analyze simultaneously different buses. The proposed index is illustrated using synthetic data and then tested using timedomain simulations on the KTH-Nordic32 system.