Improved Controller of LCL-Type Grid-Connected Inverter System Based on Active-Damping

In order to improve the control accuracy of single-phase LCL grid-connected inverter in the case of grid frequency fluctuation, an improved current controller is proposed. The controller composed of proportional, integral, resonant and quasi resonant links combines infinite gain characteristic of resonant controller and broadband characteristics of quasi resonant controller so as to overcomes the problems that proportional-integral controller cannot realize zero steady-state error regulation, the robustness of the proportional-resonant controller to the frequency fluctuation of the power grid is very poor and the fundamental wave gain of quasi-proportional-resonant controller is not high enough. Simulation experiments show that the improved current regulator based on active damping can achieve higher control precision while ensuring effective damping when the frequency of the power grid fluctuates in a single-phase LCL-type inverter system.