Abstract
The LCL-filter is one of the methods to reduce the size of the filter inductor but it leads to resonance in the system. The resonance usually results in unstable system and triggers the over-current protection. An active damping technique based on the virtual resistor is provided in this paper. The concept and the mathematical analysis of the proposed method are explained, and then the stability of the single converter operation and multiple grid-connected converter operation are analysed. Moreover, the simulation and the laboratory experiment results are for the verification.