Study On The Silicon Carbide Inverter Based On Active Power Decoupling

Under the pressure of energy crisis and environmental pollution,the new energy power generation technology has been developed rapidly.With the development of power electronic technology,photovoltaic power generation as a representative of the new energy generation field is becoming increasingly popular.The progress of power electronic technology is closely related to the development of power devices.Silicon carbide(SiC)power devices with its high switching speed,small conduction loss and high blocking voltage,more adapt to the development of power electronic technology,attracting more and more attention.This paper researches on the characteristics of SiC power devices,and analysis the problems of high switching frequency of inverter system.Then the driving circuit and experimental platform are optimized,and the power coupling problem of DC bus is studied.The characteristics of SiC power devices are different from those of Si power devices.In this paper,the dynamic and static characteristics of SiC MOSFET devices are analyzed and compared with the Si MOSFET.The double pulse experimental platform is built,and the related characteristics of SiC MOSFET are studied.The high switching speed of the SiC MOSFET enables the inverter to operate at a higher switching frequency.However,the large rate of voltage and current at the turn-on and turn-off time makes the parasitic parameters have a great influence on the devices.At the same time,the crosstalk phenomenon is more serious when the switching frequency is high.In this paper,the influence of parasitic parameters and the crosstalk phenomenon are studied.Then the influence mechanism of parasitic parameters and the particularities of SiC MOSFET are analyzed.In order to solve the problem of high switching frequency,the driver circuit and inverter circuit are optimized and analyzed through experiments.The high switching frequency enables the inverter to operate at a higher power density.However,in the single-phase inverter,the DC bus has secondary voltage fluctuations.The inverter needs larger DC bus capacitor to decouple the power,which is not good for the power density.In this paper,the principle of secondary voltage fluctuation of DC bus is analyzed,and the different power decoupling methods are compared.Then the principle of active power decoupling and mathematical model is analyzed,and the control algorithm of active power decoupling topology is improved.The method effectively suppresses the voltage fluctuation of the DC bus and improves the quality of the inverter output current.In this paper,a silicon carbide inverter based on active power decoupling is built and the optimization of SiC MOSFET drive circuit,controller and sampling circuit are completed.The switching frequency of the inverter is 50 kHz,and finally the active power decoupling method is verified through experiments.