Abstract: In order to solve the instability problem of the LCL grid connected inverter system under weak grid, a new phaselocked loop structure based on linear active disturbance rejection control（LADRC） is proposed from the perspective of impedance regulation. The structure aims to reshape the equivalent output impedance phase characteristics of the inverter grid-connected system,to realize the frequency and phase synchronization stability control of the inverter system. The new phase-locked loop structure combines LADRC and fixed-frequency SOGI（FFSOGI） technology to reshape the output impedance of the inverter. The phasefrequency characteristics of the equivalent output impedance of the inverter are improved within the feasible range of the phase angle, thereby enhancing the adaptability of the inverter system to the grid impedance. The simulation and experimental results show that the proposed new phase-locked loop structure has good transient response speed and steady state filtering ability. It can not only realize an accurate phase-locked loop under weak grid, but also reshape the output impedance of the inverter system, which effectively broadens the system’s adaptability to grid impedance.