Design of Grid-connected Inverters With LCL Filter Based on PI Regulator and Capacitor Current Feedback Active Damping

The active damping based on capacitor current feedback is an effective way to damp the resonance caused by the LCL filter in the grid-connected inverters.Besides,PI regulator is widely used to control the injected grid current for its simplicity and effectiveness.Based on the PI-based injected grid current regulator and capacitor-current-feedback active damping,the effects of the controller parameters on the specific requirements of the LCL-type grid-connected inverter,i.e.,steady-state error,phase margin,and gain margin,were investigated in this paper.A step-by-step method was proposed to obtain the entire parameter regions that meet the requirements aforementioned.Based on these parameter regions and specific application requirements,the appropriate injected grid current regulator and feedback coefficient of capacitor current could be obtained without try and error procedure.The proposed method can yield a proper controller which ensures effectively damped,highly robust,fast transient-response and low steady-state-error system.Experimental results verify the effectiveness of the proposed design method.