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Compared with traditional Z-source and quasi-Z-source inverter, tapped-inductor quasi-Z-source inverter (TL-qZSI) has higher booster multiple, lower capacitance stress and higher conversion efficiency. Therefore, it is very suitable for grid-connected photovoltaic power generation system. This paper analyzes the voltage boosting theory of the TL-qZSI and applies it into grid-connected photovoltaic power generation system. For the imbalanced power grid voltage sag situation, this paper puts forward a low voltage ride-through (LVRT) control strategy. System realizes the unity power factor running and has a good LVRT ability under imbalanced power grid voltage sag. At last, the simulation and experimental results are shown to verify the correctness of the control method.

An improved quasi-Z-source inverter for grid-connected photovoltaic system is proposed in this study. Two tapped-inductors are substituted for the inductors of quasi-Z-source inverter (qZSI) respectively. Compared with the classic topology, the proposed topology can not only arise the boost ability but also make the voltage stress be decreased. The operation principle and voltage stress of the proposed topology is analyzed theoretically and compared with that of qZSI and switched-inductor quasi-Z-source inverter (SL-qZSI). The results of simulations and experiments are shown to validate the feasibility of the proposed topology.