Abstract: In the light of harmonic resonance and stable operation of LCL converter system,a control strategy of converter based on cascade improved active disturbance rejection is proposed. Firstly,the mathematical model of three-phase LCL converter in dq coordinate system is established;Then,based on the linear ADRC strategy,the observer decoupling design method is introduced to form an improved ADRC strategy to enhance the resistance of the system to harmonic resonance;Finally,a double closed-loop control strategy combining improved active disturbance rejection and traditional active disturbance rejection is formed,and simulation model is built to verify. The results show that the system under the cascade improved active disturbance rejection control has better harmonic resonance suppression effect and stability ability compared with the traditional third-order active disturbance rejection and proportional integral control.