An Accurate Resonant Frequency Design Method Considering Digital Control Delay in Grid-Connected Converters

Extensive solutions have been proposed to damp LCL resonance, where active damping (AD) schemes based on a single filter variable feedback have been shown to be effective and flexible. This paper presents a study of such AD techniques, where a virtual impedance model is unified for four commonly used inner loop feedback state variable and a unified analysis method is proposed. Consequently, the quantitative relationship between controller parameter and actual resonant frequency is revealed, which is meaningful for control system design. Finally, the effectiveness and accuracy of the proposed method are verified by system bode diagram design results.