Active damping of resonance oscillations in LCL-filters based on virtual flux and virtual resistor

This paper presents several methods for active damping of resonance oscillations in LCL-filters. All the methods are implemented using only estimated values of the capacitor voltages and currents. The sensorless control strategy used in this paper is based on the virtual flux concept and all voltages and currents with the exception of the dc bus voltage and the converter output currents are derived from the virtual flux. The presented theory is then verified experimentally in the lab.