Active damping of LCL filter without capacitor voltage sensors for three phase PWM inverter

In this paper, new sensorless active damping method of the grid-connected LCL filter for a three-phase PWM inverter is proposed. The resonance component of capacitor voltage of LCL filter is observed by a simple MRAS (Model Reference Adaptive System) observer without additional sensors or circuits. The active damping is implemented by feed-forward compensation of the observed capacitor voltage for current controller. The validity of the proposed method is verified by the simulation and experiment.