DC-link capacitor selections for the single-phase grid-connected PV system

The selection criteria of dc-link capacitor based on the optimal ac line current regulation strategy for the single-phase grid-connected photovoltaic (GCPV) system is proposed in this paper. The power flow of the GCPV system and the optimal ac line current regulation strategy are presented. The optimal ac line current regulation strategy can achieve dc-link voltage regulation in one ac mains cycle while minimizing the injected ac line current variation. The mathematical expression for the dc-link voltage variations and the number of ac mains cycle that the dc-link voltage stays inside the hysteresis band are derived thoroughly. The derived equations also explain the behavior of the dc-link voltage responding to the power variation of the single-phase GCPV system. As a result, the selection criteria of the dc-link capacitor can be established. Hardware experimental results have presented to verify the performance of the single-phase GCPV system.