A full-bridge LLC converter suitable for DC microgrid
In allusion to the problems of large transformer volume,high loss and high voltage stress of semiconductor devices in traditional grid-connected isolated photovoltaic converter,a high-gain DC-DC converter based on LLC resonant converter is proposed.The converter can meet the requirements of electrical isolation between input and output.By combining the full-bridge LLC resonant converter with switching capacitors,the gain of the converter is increased effectively,the volume and loss of the transformer are reduced,the voltage stress of semiconductor device is lowered,and zero voltage switching of the switching tube and zero current switching of the diode are achieved,effectively reducing switching losses.The working principle of the proposed converter is analyzed in detail,its basic characteristics are analyzed by means of fundamental wave analysis method,and the voltage and current stress of semiconductor devices are calculated and the circuit parameters are designed.An 800 W experimental prototype is built to prove the accuracy of the theoretical analysis.The experimental verification that the converter can realize ZVS turn-on of the switching tube,ZCS turn-off of the diode,and reduce the volume and copper consumption of the transformer.The highest conversion efficiency can reach 94.9%.The voltage stress of the secondary diode is 1 2 of the output voltage,which is 0.5 times that of full bridge rectification,and 0.25 times that of half bridge rectification.The average current is the same,which is beneficial for the device selection and more suitable for the applications in DC microgrids,proving the accuracy of theoretical analysis.
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维普
