The transient stability of power systems typically involves complex dynamic couplings among different generators

leading to significant challenges in quantitative stability evaluation. To address this

this paper proposes a novel order parameter- based transient stability analysis framework for large-scale power systems in this paper. First

this paper derives an approximate decoupling model of the swing equation using order parameters

and employs a Lyapunov function to quantify the stability margin of the system

providing new mathematical tools for transient stability assessment. Then

the operational states of synchronous generators under varying working conditions are systematically analyzed based on this model

revealing the impact of generator output

inertia time constant

and transient reactance on transient stability. Subsequently

a model of multiple virtual synchronous generators (VSGs) considering current-limiting effects is derived

extending the order parameter approach to multi-machine multi-VSG systems. Case studies on IEEE 1888-bus and 2383-bus systems demonstrate the effectiveness of the proposed method.