Iet Generation Transmission & Distribution | 2019
Voltage instability prediction based on reactive power reserve of generating units and zone selection
Abstract
In this study, a voltage instability prediction algorithm is proposed based on Thevenin impedance matching theorem. This algorithm consists of three important parts: an adaptive network zoning algorithm, the Thevenin-based voltage instability risk predictor (VIRP) and a third-order extrapolation technique. The zoning algorithm, based on the concept of electrical distance, is proposed to divide the main network into several zones after the occurrence of any large event. Each zone consists of some load buses and generating units have the most influences on their voltage stability. The proposed VIRP is defined similarly to the Thevenin indicator multiplied with a contribution factor. This factor is calculated for each zone, based on the lack of the reactive power reserve in its generating units, to increase the predictor value, especially in the proximity of the instability. So, VIRP could reduce the instability detection time with respect to the Thevenin indicator. The further reduction in the instability detection time is obtained by the well known cubic spline extrapolation technique. This function is applied to the values of VIRP to predict the instant of the instability. The proposed algorithm is tested on the modified New England 39-bus test system supplied with the voltage-source converter-high-voltage dc link.