Current Ripple Estimation for 3-Level ILCL Filtered Grid-Connected Inverters with the SVPWM or the DPWM Method

The improved LCL filter (ILCL) is widely applied on transformer-less 3-level grid-connected PV inverters to suppress the common current flowing into the grid. Since the neutral point of the DC bus is directly connected to the common point of the filter capacitor, the current ripple distribution with ILCL filter is different from that with the LCL filter. In this paper, we analysis the current ripple firstly for the 3-level ILCL- filtered inverter with the space vector pulse width modulation (SVPWM) or the discontinuous pulse width modulation (DPWM) in consideration of the filter inductance variation. Finally, the analysis result is verified by the experiment.