Study Of 500kHz Soft-switching SiC Single Phase Inverter

High-frequency of PV grid-tied inverters will be a trend of their development in the future.The excellent performance of SiC MOSFETs make them much potential in high-frequency applicaitions.The current status of research and application with SiC MOSFET is introduced,and the current situation of global research on high-frequency inverters is illustrated by sereval examples.In this paper,SiC MOSFET and ZVS soft-switching technique are combined,improving the working frequency up to 500kHz and maintaining a high conversion efficiency.Based on certain restrictions of ZVS full-bridge inverters on normal operation,taking the specific parameters of charateristics into account,the set of resonance parameters for 500kHz is selected.Main features of several common soft magnetic materials,especially core loss density,are compared,afterwards MnZn ferrite is determined as the core material of 500kHz filter inductors and resonance inductor.The designed filter inductors are compared with 100kHz filter inductors,which indicates that the volume of inductors get great decreased.Some design is made on the digital controlling platform.A framework of DSP+FPGA is employed,in which DSP samples the current of filter inductor and transfers the data to FPGA in parallel by utilizing XINTF and DMA,and FPGA completes closed-loop calculation as well as update of PWM comparing value.The selection on the type of DSP and FPGA is carried out,the PCB board of DSP part is drawn,which contributes the completion of digital controlling platform.The verification is made over a 1.5kW experiment model,showing that 500kHz soft-switching SiC inverter can operate normally,and the resonance process can be aroused and ZVS condition can be realized just by utilizing junction capacitor of SiC MOSFET itself,without external resonance capacitors paralleled.The conversion efficiency of 500kHz soft-switching SiC inverters is measured,and compared with that of hard-switching inverters with the same electrical parameters.It's proved that at high switching frequency,when the volume of inverters could get great decreased,a high conversion efficiency could be kept by ZVS technique.