The background harmonic and the voltage fluctuation etc usually exist in the field of grid connection. Because it is difficult to determine these complex and time-varying disturbance models

the model-based disturbance compensation method has limited effect. In addition

although the adaptive control method based on the real-time detection has strong immunity

the control algorithm is often complex. As for the active disturbance rejection control（ADRC）

the sum of the internal and external disturbance can be regarded as the generalized disturbance

which can be estimated in real time by the observer and compensated by the feedforward stage. The ADRC has the ability of resonance suppression and strong immunity

and does not depend on the accurate mathematical model. Therefore

to solve the above mentioned problems

a first-order ADRC control strategy is designed for LCL grid-connected inverter in this paper

the stability and immunity of the whole system are analyzed in detail

and the effectiveness of the control method is verified by simulation and experiments. The results show that the designed first-order ADRC strategy can improve the quality of grid-connected current

the system stability and immunity. At the same time

the designed control strategy does not need the active damping stage

and has the simple algorithm and high engineering application value.