Analysis And Research Of Resonant High Frequency Converter Based On LLC

In recent years,with the development of power electronics technology,traditional PWM inverter technology has presented numerous disadvantages,such as bulky transformers,large switching losses,slow response and unsatisfactory output AC voltage quality.The LLC resonant network with the high-frequency inverter link was integrated to design an LLC resonant high-frequency converter to ensure zero-voltage turn-on of the power switch and reduce the power device switching losses,thereby avoiding the voltage overshoot problem in the post-stage converter between high-frequency transformers and cycloconverters to ensure filter current to keep continuous and achieve natural commutation.Firstly,this paper introduces the application of DC/AC technology in the trend of new energy,elaborates the development status of the high frequency chain inverter technology and soft switching,and simultaneously analyzes the merits and drawbacks of several high frequency converter topology with and without resonance.It mainly analyzes and discusses the basic main circuit topology technology and the existing control strategy technology of the LLC resonant high frequency loop converter.Secondly,the characteristics in phase plane and time domain of the LLC series resonant circuit are studied in detail,and the discussion of the control strategies and operational principle of unipolar SPWPM(sinusoidal pulse width pulse position modulation),and buiding the mathematical model of output voltage of the inverter bridge and post-stage conversion.The correctness of the SPWPM model is also verified through Matlab simulation.Then,the mathematical equivalent model of the converter is further analyzed.By analyzing the characteristics of the small signal,the "small signal perturbation" mathematical equivalent model of the converter is further obtained.In addition,the double closed-loop control system with capacitive current as the inner ring and output voltage as outer ring is designed,and its excellence and stable effect is verified by simulation software.Finally,based on the above researchs,the hardware circuit is designed,the parameters of the converter are selected,and the related auxiliary circuit is designed to make an experimental prototype.The measured waveform is consistent with the theoretical analysis and the simulation verification waveform,and the output of the industrial frequency AC voltage can meet the actual demand.Therefore,the feasibility of this kind of converter structure design is verified,which shows that it has great practical value in the new energy inverter and has broad application prospects,which provides a theoretical basis for follow-up researchs.