The rapid control characteristics of renewable energy and other power electronic equipment have accelerated the dynamic transition of system voltage

shifting the issue of voltage stability from being solely “load-side” to a joint development involving both “source and load sides.” This evolution has led to significant changes in both the modes and processes of voltage instability. This paper systematically reviews typical scenarios of voltage instability and focuses on analyzing three new forms of voltage instability at renewable energy integration points: voltage oscillation caused by active power switching

sustained low voltage due to power reduction

and voltage oscillation induced by reactive power switching. Furthermore

it is demonstrated that the static voltage instability mechanisms at load and renewable access points exhibit a consistent nature when the system’s Thevenin equivalent resistance is neglected. The differentiated impact of Thevenin resistance on the static voltage stability of sending and receiving systems is also analyzed. On this basis

the study summarizes novel transient voltage instability mechanisms introduced by renewable energy disturbances. An engineering-oriented quantitative assessment method for transient voltage instability risk is proposed. The findings of this work provide theoretical support for understanding and managing voltage stability in new-type power systems.