LCL inverter has been widely used in grid connected application for renewable power generation. In weak grid

mismatch between grid impedance and control parameters may decrease the system stability

or even lead to instability.Taking the degree of mismatch into account and based on the current double closed-closed loop control model

we analyzed the mechanism of grid impedance affecting the system stability and proposed an improved method of network-side series virtual inductance. The effect of grid impedance on system stability was reduced by increasing the equivalent filter inductance at the grid side before designing the control parameters

which enhances the system stability. The conventional and improved control strategies were compared and analyzed by the Bode diagram and root locus method. The results show that

under the same condition of weak grid

the improved method has better system stability. In addition

the improved method can allow the grid impedance to fluctuate in a larger range and improve the system’s adaptability to weak grids. The above conclusions are verified by Matlab/Simulink simulation.