A High Efficiency and High Power SiC DC-DC Converter Based on Interleaved-Boost and Full-bridge LLC Integration for PV Applications

In the application of photovoltaic power generation integrated into the MVDC grid, the design of high-power and high-voltage converters is often a difficult point due to the limitations of devices and converters themselves. Aiming at high efficiency, adaptive voltage regulation and high power density, the interleaved-Boost and full-bridge LLC converter (IB-FBLLC) based on all SiC devices is studied and designed. For the core topology, LLC topology, a parameter design method based on high efficiency and wide bus voltage range is proposed. The losses of each part of the LLC converter as a function of main parameters are analyzed in this paper, and it is concluded that the switching loss is independent of the frequency when considering the maximum efficiency. In the design based on the wide bus voltage range, the FHA method is innovatively applied to the decoupling solution of resonance parameters by introducing intermediate variables k and Q, which significantly optimizes the parameter design process and simplifies calculations that are almost impossible to solve. It turns out that the maximum voltage gain or minimum bus voltage is independent of the switching frequency. These design methods and considerations are verified on a 80kW prototype, whose efficiency and power density reaches 98.08% and 1.562 W/cm
³
, respectively.