Three-phase High Frequency And High Power Density Converters Based On GaN HEMTs

With the rise of new energy,wireless charging,data centers and other fields,new pursuits for converter efficiency and power density have been aroused,and traditional silicon devices have been difficult to meet the demand.GaN has begun to rise rapidly due to its advantages in volume,efficiency,and switching frequency.In order to make GaN devices better in the future market,this article designs a three-phase two-level converter prototype for GaN Systems’ GS66508T.First,it introduces the GaN device,understands the difference between it and the silicon device,and analyzes the principle of its turn-on and turn-off.The drive characteristics,output characteristics,and transfer characteristics of the device are described in detail,and the distributed capacitance between the electrodes and the operating mode are analyzed.A double-pulse test platform based on GaN HEMT is built,and its switching transient characteristics are obtained through simulation and experiment.Then,the switching speed,switching loss and EMI of the GaN HEMT under different external drive resistances and different load currents were tested through experiments.The crosstalk phenomenon was modeled,and the effects of different external drive resistances and different load currents on the crosstalk were tested through experiments,and several measures to suppress the crosstalk were proposed.Next,the loss of the GaN HEMT three-phase two-level converter is modeled,and its on-state loss model,switching loss model and output capacitor loss model are analyzed.The expression of on-state loss under SPWM control and SVPWM control strategies are deduced in detail.In order to obtain the switching loss of the converter more accurately,the relationship between the switching loss and the load current in the operating current range of the converter was tested through experiments,and the expression of the switching loss was derived.The principle of loss caused by output capacitance is introduced,and the influence of parasitic parameters on loss is analyzed,and the expression of output capacitance loss considering external parasitic capacitance is obtained.The experiment obtains the loss of the converter at different switching frequencies.By comparing with the theoretically deduced loss,the correctness of the proposed model is verified,and then the reason for the error of the theoretical model is analyzed.Finally,an experimental prototype of a three-phase two-level converter based on GaN HEMT was built.The power loop and drive circuit of the converter are designed,and the selection method of some components is introduced.Through simulation,the influence of several important parasitic parameters on the converter is obtained,and the corresponding optimization method is given.In order to ensure that the converter can operate stably,the heat dissipation system is designed,and the heat sink is simulated by FloTHERM.Several challenges brought about by high switching frequency are proposed,and corresponding solutions are given.Then,the output voltage and current of the converter at a switching frequency of 300 kHz,an output power of 3 kW,a switching frequency of 600 kHz,and an output power of 1.5 kW were tested through experiments.The peak efficiency of the converter at this time was 97.06% and 94.42%.Analyzed the reduction ratio of the passive components of the converter caused by the high switching frequency,which showed the advantages of GaN HEMT devices.The paper has 65 pictures,4 tables,and 92 references.