Energy Potential Field and Transient Stability Analysis for Grid-Following Converter Based on Energy Function

Phase-Locked Loop (PLL)-dominated gridfollowing converter systems are prone to transient problems such as synchronous instability and power angle oscillations in weak grid environments, which seriously threaten the safe and stable operation of power systems. To address the above problems, this paper proposes an energy function-based transient stability modelling and parameter sensitivity analysis method for phaselocked loops from the perspective of constructing a synchronous generator-like power angle model. By modelling the interaction between the converter and the grid, the second-order power angle swing Equation with the characteristics of a synchronous generator is derived, and the total energy expression of the system is constructed by introducing the Lyapunov-like energy function, so as to establish a stability criterion with physical interpretation. On this basis, the influence of the key parameters of gridconnected inductance and active current component on the shape of the energy function and the structure of the attraction domain is systematically analyzed, and the coupling between them and the short circuit ratio (SCR) is clarified. The parameter sensitivity simulation model is further constructed to visualise the variation of the attraction domain under different parameter conditions through 3D energy function plots. By comparing the voltage-dip response waveforms under different short-circuit ratio conditions, the conclusion that the decrease of short-circuit ratio leads to the degradation of energy structure and the significant weakening of transient stability is further verified.