Active Disturbance Rejection Control Of Current Loop For LCL Grid-connected Inverter

The grid-connected system is a complex system with strong uncertainty and nonlinearity,and its control method directly affects whether the grid-connected system can operate safely,stably and with high quality.In this paper,the LCL gridconnected inverter is selected as the control object,and according to the Linear Active Disturbance Rejection Control（LADRC）,the current loop control strategy based on LADRC is designed,the details are as follows:（1）Aiming at the resonance problem of LCL type grid-connected inverter,a third-order active disturbance rejection current controller is designed.Through the fourth-order Linear Extended State Observer（LESO）,the uncertainty and the disturbance is observed and compensated,and the controlled object is restored to the standard integral series type.The tracking performance and disturbance immunity of the system are analyzed in detail using the frequency response method,and the Lyapunov stability criterion is used to prove that the closed-loop system is asymptotically stable,and the stability domain of the linear active disturbance rejection controller is obtained,which provides a reliable theoretical basis for parameter design.The simulation results show that the designed current control strategy improves the quality of grid-connected current and the robustness of the system.（2）In the distributed generation background based on large-scale development of renewable energy,the grid-connected system is prone to time-varying disturbances such as grid side voltage fluctuation,high background harmonic and parameter perturbation,which makes the control method based on model compensation difficult to maintain the stability of the system.Therefore,an internal model control strategy based on disturbance compensation is designed for LCL grid-connected inverters.Based on the traditional internal model control（IMC）,the idea of active disturbance rejection control（ADRC）is integrated,and the linear extended state observer is added to compensate the disturbance in real time,which improves the dynamic performance and robustness of IMC when the model is mismatched and the disturbance is changed in time.Through theoretical analysis,the stability and immunity of the grid-connected system under the proposed control strategy are demonstrated in detail,and the reliability of the control strategy is verified effectively by simulation comparison.