Virtual RLC active damping for grid-connected inverters with LCL filters

This paper presents a virtual RLC damper for resonance damping in an LCL-type grid-connected voltage source inverter by capacitor current feedback through a second-order high pass filter. The proposed method can achieve good damping performance and enhance the system stability by inherently compensating phase lag around the resonant frequency introduced by digital time delay. Moreover, the analysis in this paper proves that the existing virtual RC damper method is a special case of the proposed method. The parameter design principle for the RLC damper is also investigated. The analysis and the effectiveness of the proposed scheme is verified with simulation results.