Research On Three Phase LCC Series-parallel Resonant Converter

In this thesis,a three phase LCC series-parallel resonant topology is employed as the basic topology for some applications with a requirement of wide output voltage range and constant output power.A power supply with constant output power based on pulse frequency modulation(PFM)is presented.Through the analysis of the working proc ess of the converter,the basic principle of achieving ZVS soft switching of the converter is obtained.Through the analysis of simulation results,the working principle of the converter and the realization principle of the soft switch ing are further understood.Considering the complexity of the three phase circuit analysis,the single phase simplified equivalent circuit is obtained by simplifying the circuit of the three phase LCC converter.The steady-state characteristics of the single phase simplified equivalent circuit are analyzed by fundamental harmonic analysis(FHA),and then the gain characteristics and input impedance characteristics of the converter are obtained.The relevant steady-state characteristic curves of the converter are drawn by simulation software,which include gain curve,input impedance curve,constant power curve,etc.Through the analysis of the curves,a more in-depth understanding about the converter's steady-state characteristics and the work process is obtained.The effect of the different range of quality factor Q and different value of the series-parallel capacitance ratio Cs/Cp on the converter's performance is analyzed by comparative experiments.A power supply with input voltage of 100 V,output voltage range of 354 V-707 V and constant output power of 2500 W is built.The closed-loop control of the converter is achieved by PFM control which is realized by analog circuits.The correctness of the theoretical analysis is verified by analyzing the closed-loop results of the converter.Finally,the constant power output capability of the converter when the load changes is verified by cutting experiment,and the stability of the system is verified.The experiment has achieved expected results.