An enhanced voltage stability index with the influence of voltage magnitude regulating transformer

Given the expanding power transmission networks and escalating demand, continuous voltage stability assessment is crucial for maintaining secure and reliable power system operation. Despite the availability of various voltage stability assessment techniques, their effectiveness can be hindered by an inadequate representation of certain power system components, notably voltage magnitude regulating transformer devices, especially in operating conditions near voltage collapse. This shortcoming is further compounded by the limitations of existing voltage stability indices, many of which either demand significant computational resources or exhibit inconsistent performance across diverse operating scenarios. This paper develops an innovative indicator for precise voltage stability assessment in transmission networks. Unlike existing indices with restrictive assumptions, the proposed index enables accurate evaluation of voltage stability with minimal preconditions. Furthermore, the presented index incorporates the impact of voltage magnitude regulating transformer. The performance of the introduced index was analyzed through an assessment performed on two benchmark transmission systems (two-bus and nine-bus) under a range of operational conditions. Simulation results demonstrate that the proposed index outperforms other widely used indices. The findings demonstrate the model's ability to accurately assess the impact of voltage magnitude regulating transformers.