DC-Link Power Ripple Mitigation of Three-Phase Grid-Tied Inverters With Virtual Phase-Current Regulation

In this article, to mitigate the double-line frequency power ripple at dc-link caused by unbalanced grid voltage conditions, a developed virtual phase-current regulation (VPCR) method has been proposed for three-phase grid-tied inverters. The proposed method is featured with an optimized virtual phase current gain in the current feedback of the fault phase. To realize the gain value optimization, an improved output current calculation method has been presented. And consequently, a precise power ripple derivation has been carried out at both point of common coupling (PCC) and dc-link. Due to the introduction of unbalanced three-phase currents by VPCR, it is found that there exists an obvious difference between the power at PCC and dc-link. A parameter tuning is then performed to enhance the mitigation capability of dc-link power ripple. With the developed VPCR, the inverter exhibits a stronger mitigation capability under the condition of high voltage drops. All theoretical analyses have been verified by both simulation and experimental results.