| With the rapid consumption of the earth's resources and the deterioration of the natural environment,new energy power generation has attracted more and more attention,among which solar photovoltaic power generation develops most rapidly.DC-DC converter is an important part of photovoltaic power generation system.Solar panels have the characteristics of wide output voltage range,which will affect the normal operation of the latter stage DC-DC converter.Therefore,it is of practical significance to study DC-DC converters with wide input and excellent performance for photovoltaic power generation.In view of the wide input voltage range of DC-DC converters in photovoltaic,fuel cell and other new energy power generation systems,based on passive lossless soft-switching technology,the wide input range Buck-Boost converter and its performance improvement methods are studied.Non-minimum voltage stress(NMVS)and minimum voltage current stress(MCVS)passive lossless soft-switching units are applied to Buck-Boost converter respectively to realize normal DC-DC conversion and reduce switching losses.The system adaptability is improved by using different characteristics of passive lossless soft-switching topology and reasonable parameter design method.Firstly,the working principle of Buck-Boost converter with soft-switching unit is analyzed,and the working modes of two kinds of passive lossless circuits in one cycle are analyzed in detail.The critical relationship between the working modes of NMVS passive lossless soft-switching Buck-Boost circuit and resonant inductance current is pointed out,and the working modes of two different cases are discussed.A design method of inductance and capacitance parameters of main circuit and soft-switching unit is proposed for the converter working in dynamic range with output voltage as variable parameters.The simulation results show that two passive lossless soft-switching Buck-Boost converters achieve zero-voltage switching and zero-current switching,and the rationality of the parameter design method is verified.Sex.Subsequently,the Buck-Boost converter circuit is modeled in non-ideal small signal condition,and the compensation network is designed to improve the stability of the system.The closed-loop simulation results show that the working mode and output steady-state performance of the system meet the requirements.Finally,the experimentalplatform of Buck-Boost converter is built,and an experimental prototype with 14V~36V input and 24V/1.5A output is designed.The dynamic range of the converter is tested.The experimental results show that the system has good static and dynamic performance,which verifies the rationality of the controller design.The conversion efficiency of the converter before and after adding soft-switching in the worst condition with wide input is compared.The results show that the conversion efficiency can reach more than 88% in the wide input voltage range.The conversion efficiency is 5% higher than that of the traditional Buck-Boost converter.The experimental waveforms of other parameters of the soft-switching unit are also consistent with the simulation results,The correctness of theoretical analysis and parameter design is verified. |
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