Design and implementation of high efficient two-stage three-phase/level isolated PV converter

This paper presents the design and implementation of an ultra-high efficient two-stage PV converter consisting of full-bridge DC/DC converter as the first stage and three-level T-type DC/AC inverter as the second stage. Firstly, the operation principles of full-bridge DC/DC converter and DC/AC converter are given in this paper. Then the control algorithm of the converter is analyzed and implemented. For the DC/AC converter, the impacts of both modulation strategy and device technology on efficiency are discussed and investigated. Finally, a 10kW/300V two-stage PV inverter consisting of a full-bridge DC/DC converter based on all SiC devices and T-type inverter based on hybrid devices is built. The impacts of different factors such as the transformer turn ratio of the DC/DC converter and DC-link voltage on the efficiency are evaluated by experiment. Efficiency values of 97.1%, 99.2% and 95.9% are achieved for the DC/DC stage, DC/AC stage and the overall system, respectively.