Comparative evaluation of coupling L-CL filter for interleaved three-phase voltage source inverters

In this paper, the combinations of coupled inductors (CIs) and LCL filters are comparatively investigated for grid-connected interleaved three-phase voltage source inverters (VSIs) in terms of the resonance phenomenon. In current-controlled direct parallel VSIs, two current controllers are required for the power flow and the circulating currents. Therefore, the stability of both current controllers are evaluated for three possible configurations of CIs and LCL filters. As a result, the resonance frequencies vary with the placement of the parallel capacitors and the grid-side inductors. A configuration for reducing the effect of the resonance on the system stability is proposed, and the stable operation of the proposed configuration is simply achieved without additional losses by passive or the controller complexity by active damping. The three possible combinations of CIs and LCL filters are simulated and the proposed configuration is experimentally verified.