A voltage security region (VSR) is a powerful tool for monitoring the voltage security in bulk power grids with high penetration of renewables. It can prevent cascading failures in wind power integration areas caused by serious over or low voltage problems. The bottlenecks of a VSR for practical applications are computational efficiency and accuracy. To bridge these gaps

a general optimization model for tracking a voltage security region boundary (VSRB) in bulk power grids is developed in this paper in accordance with the topological characteristics of the VSRB. First

the initial VSRB point on the VSRB is examined with the traditional OPF by using the base case parameters as initial values. Then

the rest of the VSRB points on the VSRB are tracked one after another

with the proposed optimization model

by using the parameters of the tracked VSRB point as the initial value to explore its adjacent VSRB point. The proposed approach can significantly improve the computational efficiency of the VSRB tracking over the existing algorithms

and case studies

in the WECC 9-bus and the Polish 2736-bus test systems

demonstrate the high accuracy and efficiency of the proposed approach on exploring the VSRB.