Multi-converter Combined System Design And Power Sharing Strategy Research

DC high-voltage conversion technology has a wide range of applications in aerospace power supply systems,DC microgrid systems,and ocean power remote power supplies.However,blindly improving the withstand voltage level of converter components is contrary to the current trend of miniaturization of power electronic converters,and brings great challenges to the insulation,component selection,and stability design of the converter system.In order to solve the above problems,by connecting the input and output terminals of multiple converter modules in series and parallel,a new type of converter with superior performance and low cost can be constructed to solve the problem of high voltage level,which has become a research hotspot in the field of power electronics.To improve the withstand voltage level of the input end of the converter,and to make it have high reliability,high dynamic response,and other characteristics,in this dissertation,the input-series output-parallel(ISOP)of multiple converter modules is constructed into a new type of ISOP combined converter.,and in-depth research on key technologies such as the selection of the basic module topology and the design of the converter’s input voltage equalization and output current equalization control strategy.First of all,for the basic module topology selection,this article compares five types of bidirectional converters,and selects dual active full-bridge DC/DC converters(DAB)according to the withstand voltage level,switching frequency,and soft switching aspects.For the basic module.Subsequently,the four working modes of DAB converters based on single phase-shift(SPS)in a working cycle are analyzed,and mathematical modeling is carried out to deduce the current and power of DAB converters.Expression,and its soft switch range.Secondly,in view of the uneven power distribution of the input series output parallel combination converter,the relationship between the input voltage sharing(IVS)and output current sharing(OCS)of the ISOP combined converter is established.,Established that the input voltage equalization is the core condition for the stable operation of the converter.The ISOP converter voltage equalization scheme based on double closed-loop control is proposed,and the basic module and the ISOP combined converter are modeled and analyzed respectively.The input voltage equalizing loop and output voltage loop are designed to establish a theoretical basis for building the ISOP combined converter simulation model and experimental prototype.Finally,a simulation model of a multi-module ISOP combined converter based on dual active full-bridge DC/DC converters was built on the MATLAB simulation platform,and simulation experiments were carried out for input voltage fluctuations,load changes,and inconsistent converter parameters.On this basis,the software and hardware design of the ISOP combined converter is carried out,and two DAB converter module input series and output parallel prototype platforms are built,and experimental verification is carried out.Simulation and prototype experiments show that the ISOP combined converter based on the dual closed-loop control strategy designed in this dissertation has excellent input voltage equalization and output current equalization effects,and achieves the original design intention of power equalization of each basic module.