Application Of SiC MOSFET In Three Level Grid Connected Inverter

The SiC MOSFET has low on state resistance and low switching loss, which makes the SiC MOSFET inverter more efficient and smaller. In this paper, based on the three level grid connected inverter, the application of SiC MOSFET is studied.Firslly, in this paper the basic requirements of SiC MOSFET driver was analyzed, and the relevant parameters of the drive circuit were determined by using the SiC MOSFET netlist model of ROHM company. On this basis, a SiC MOSFET driver board with optical isolation was designed, and its working principle was analyzed. Using the driver board, the switching characteristics and heat loss characteristics of two types of SiC MOSFET were tested. Through the compare and analysis, SCH2080KE was selected as the main circuit device of the three level grid connected inverter.Secondly, the voltage unbalance of the same bridge arm power device was a serious threat to the safe operation of the SiC MOSFET three level grid connected inverter. In this paper, eight kinds of operating modes were used to analyze the causes of voltage unbalance, and a new type of voltage balance circuit was designed, in which shunt asymmetrical capacitors was used in the same bridge arm. Then, three different types of clamping diodes were used to complete the experiment. The experimental results show that the proposed method is correct and effective. At the same time, aiming at the high frequency interference caused by parasitic parameters, a kind of RC suppression circuit is designed, which has obvious inhibition effect.Finally, the PCB circuit of the SiC MOSFET three level inverter based on TMS320F28335 control system was designed in this paper, and the grid connected operation of SiC MOSFET three level inverter was completed. The design and algorithm were verified.