Abstract:When grid-following (GFL) and grid-forming (GFM) converters are interconnected with the grid, they are mutually coupled through the grid impedance. During grid faults, the transient behavior of these converters becomes intricate due to the presence of coupling terms. Instabilities in one converter can propagate to the other, posing challenges to fault ride-through capability. This paper presents a mathematical model for a hybrid grid-tied system comprising two converters, investigates the conditions for equilibrium points, and employs phase-plane analysis to elucidate the mutual influence mechanism during faults. Additionally, for GFM converters, a method is proposed to mitigate power angle deviations based on voltage drop magnitude, and to adjust the output voltage in response to the power angle and injected current from GFL converters. For GFL converters, a Phase-Locked Loop (PLL) based on GFM is introduced to facilitate hybrid fault ride-through control. The proposed approach ensures that GFM converters contribute reactive current support to the grid during faults, while GFL converters adhere to grid guidelines for current injection, thereby preventing overcurrent and phase angle instability in both converters. Simulation results validate the correctness and effectiveness of the proposed control strategy.