Operation of dual-input central capacitor photovoltaic inverter under unbalanced grid voltage condition

摘要

To date, a family of series-connected boost converter (SCBC) with enhanced efficiency has been presented as the front-end dc/dc stage of distributed photovoltaic (PV) inverter, which suffers the severe PV voltage/power oscillation when operated under unbalanced grid voltage condition. This paper proposes an operational scheme to enhance the performance of one type SCBC, namely the dual-input central capacitor (DICC) converter, under unbalanced grid voltage condition. The PV voltage/power oscillation is eliminated using the propose scheme, resulting in the maximum PV energy harvest and enhanced grid current quality even under severe unbalanced condition. Also the overall dc-link voltage oscillation amplitude is minimized. The analytical representation of double line-frequency current along with the DICC circuitry model are studied, so that the DICC circuitry parameters could be designed accordingly. This paper further proposes the control strategy of DICC-PV inverter under unbalanced grid voltage condition. All the theoretical findings and the control method proposed can be derived to other type SCBCs. Finally, the theoretical findings were verified through both Matlab simulation and an experimental prototype.