Resonance Active Damping Methods for Grid-Connected Inverters: Robustness Assessment Based on Sensitivity Function

Robustness is a critical issue for grid-connected inverters controlled with active damping techniques. This occurs since the active damping methods are designed considering the rated parameters of the LCL filter connecting the converter with the network. In this paper some of the most famous resonance active damping methods are considered and their performances are compared on the basis of the sensitivity function providing information about robust stability. Active damping techniques based on filters such as notch filter and biquadratic filter exhibit high risk instability. Active damping methods based on additional sensors such as virtual resistor and lead network provide robustness to the control systems. These conclusions are supported by simulation and experimental results in presence of significant variation of the LCL filter parameters.