Robustness analysis of active damping methods for an inverter connected to the grid with an LCL-filter

Grid-connected converters usually employ an LCL-filter to reduce PWM harmonics. To avoid the well-known stability problems it is requested to use either passive or active damping methods. Active damping methods avoid losses and preserve the filter effectiveness but they are more sensitive to parameters variation. In this paper the robustness of active damping methods is investigated considering those using only the same state variable (grid-side or converter-side current) normally used for current control (filter-based) or those methods using more state-variables (multiloop). Simulation and experimental results validate the analysis.