Dual Feedback Active Damping Method for Grid-Connected LCL Filter Resonance

This paper proposes a new active damping method for LCL filter resonance. The proposed method employs a dual feedback loop of the capacitor voltage and the grid current. Based on the proposed method, non-minimum phase behavior can be avoided over a wide range of resonant frequencies. Co-design procedures for both the active damping loops along with the fundamental current regulator are introduced. The proposed method is derived in continuous time domain as well as discussed in discrete form for digital implementation. The performance of the proposed method is verified numerically at different values of resonant frequency. Moreover, simulation work is presented to confirm the numerical results.