<p>The inherent resonance of LCL-type grid-connected inverters can lead to system instability, while active damping of the capacitor current can effectively suppress this resonance. However, in digital control systems, control delay alters the characteristics of active damping, causing the equivalent parallel impedance to vary with the frequency. When the resistive component of the equivalent impedance exhibits a negative resistance characteristic, it adversely affects system stability. In weak grids, fluctuating grid impedance can even result in system instability. Moreover, control delays induce phase lag, which affects the bandwidth of the control loop. Therefore, this paper proposes a phase advance delay compensation strategy that effectively increases the boundary frequency between positive and negative resistance of the equivalent impedance, enhancing the robustness of the system against variations in grid impedance. Additionally, a stability analysis of the system is conducted, and a method for designing the control parameters of the system is presented. Finally, simulations and experiments based on design examples validate the correctness of the theoretical analysis and the effectiveness of the proposed control strategy.</p>