After system disturbances

the rotor angle oscillation of synchronous machines may cause voltage fluctuations at adjacent grid connection nodes of renewable energy sources (RESs)

periodically triggering low voltage ride-through (LVRT) control. The activation and deactivation of LVRT controls

in turn

affect the dynamics of the synchronous machine’s rotor angle swing

leading to transient rotor angle instability risks. To investigate the impact of LVRT switching on rotor angle stability during subsequent swings

assuming the first swing is stable

this paper first establishes a transient stability analysis model for the RES and SYNs combined system. Then the analytic relationship between the rotor angle of synchronous machines and the voltage of RES grid connection points is derived to obtain switching conditions for LVRT control represented by state variables. Subsequently

the changes in transient energy of the synchronous machine during periodic LVRT switching are analyzed by the transient energy function method to reveal the mechanism of the synchronous machine’s rotor angle multi-swing instability. Afterward

an assessment method for the conservative stability boundary of the switching system is proposed. Finally

the correctness of the theoretical analysis is verified through time-domain simulation.