Identification of voltage stability critical injection region in bulk power systems based on the relative gain of voltage coupling

This study proposes a novel adaptive identification method for the voltage stability critical injection region (VSCIR) in bulk power systems. From the viewpoint of a multi-input multi-output system, a power system can be partitioned into load and generator coupled subsystems, and the concept of voltage coupling relative gain (RG) is introduced to determine the VSCIRs. A two-stage partitioning method of VSCIR is presented. In the first stage, the voltage stability weak buses are determined through loading margin and are identified as critical buses in the system. For each critical bus, the load and generator buses that have strong voltage coupling are identified through the cross-RG and clustered into a VSCIR centred by the corresponding critical bus as pilot buses. In the second stage, practical VSCIRs are obtained through (i) merging VSCIRs that have strong coupled pilot buses, and (ii) allocating the buses that are shared by multiple regions to the most coupled VSCIRs. Further, this study proposes a voltage control strategy for improving the voltage stability of the system based on the practical VSCIRs. The proposed method is tested on the New England 39-bus system, as well as the bulk 2383-bus Polish power grid.