Abstract：In LCL-type grid-tied inverters, the capacitor-current-feedback active-damping method can suppress the LCL-filter resonance effectively. However, the digital-control-delay changes the effect of capacitor-current-feedback active-damping, thus affects the system robustness against grid impedance. To weaken the adverse effects of the digital-control-delay, this paper proposes a phase-lead compensation method to compensate the control-delay of capacitor-current-feedback. By analyzing the system stability under different resonant frequencies, the gain margin requirements can be always satisfied and the compensator parameters are designed. Next, to ensure the system stability under variable grid impedances, the design of capacitor-current-feedback coefficient is developed. When adopting the selected coefficient, the closed-loop pole maps with and without phase lead compensator are analyzed. Finally, a 1kW prototype has verified the proposed theoretical analysis.
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2018, Vol. 33 
