Research on Control Strategy Based on Second-order Linear Active Disturbance Rejection Control for LCL-type Grid-connected Inverter

The grid-connected system is characterized by nonlinearity, strong coupling and uncertainty, and the current output from the grid-connected inverter has a large number of harmonics and cannot be directly connected to the grid. Therefore, usually, LCL filter is added between grid-connected inverter and power grid, but there is resonance problem in LCL filter. The self-anti-disturbance strategy predicts and compensates the uncertain factors affecting system control as accumulated disturbances, and can modify the original system to an integral series type to obtain the desired control performance. Therefore, based on the mathematical model of LCL filter, the second order linear active disturbance rejection control (LADRC) is designed, and its tracking ability and anti-interference ability are analyzed. Finally, The simulation results verify the adopted strategy.