Optimization of weighted current control for grid-connected LCL-filtered inverters

The under-damped resonance in the grid-tied LCL-filtered inverter yields much difficulty in designing the controller. One interesting solution is that if the weighted average of currents through two inductors is fed back, the close-loop control based on the feedback of the weighted current is easily designed to maintain satisfactory dynamic. However, it has been proved that under-damped conjugate poles still exist in the injected grid current. The inhibitions of harmonics around the resonance frequency are poor and the transient performance is weakened. Thus, the weighted average current control needs to be improved. Then, the damping methods are further explored. It has been demonstrated that the extra damping method are decoupled from the tracking controller of the weighted current control, that is, they are in charge of increasing the damping factor and tracking the reference separately. In summary, the improved method is capable of reducing the sensitivity to the disturbance and improving the current quality.