A Virtual RC Active Damping Method in Weak Grid for Three-level Three-phase Grid-connected Inverters

The paper investigates damping solution of LCL filter in weak grid for T-type three-phase three-level grid-connected inverters. A virtual resistance capacitor (RC) in parallel with the filter capacitor active damping method has been presented under weak grid condition. The virtual RC damping item is inserted by feeding back the capacitor current through using differential filter capacitor voltage. In order to well protect the inverter in case of over current, inverter-side current feedback closed loop control has been used. It is needed to sensor only one inverter-side current for implementing feedback control and performs the necessary active damping of LCL resonance due to weak grid, which is the attractiveness of the proposed active damping method. Performance of the proposed active damping method has been test in the laboratory rated at 15 kW, and the effectiveness and validity of the proposed method is verified with experimental results.