The Research And Implementation Of Three-phase Inverter Based On SiC MOSFET

Along with the rapid development of all-electric missile weapon system, electric actuator system will become the new rudder control mechanism. Because of the advantages in structure and control performance, rare earth permanent magnet motor becomes the first choice of driving motor for electric actuator system. It is very important to study rare earth permanent magnet motor drive system miniaturization for improving the performance of electric actuator system. In this thesis, one kind three-phase inverter based on Si C MOSFET used for driving rare earth permanent magnet motor is designed. It can provide foundation for the miniaturization of rare earth permanent magnet motor drive system, in order to expand the application range of electric actuator system in weapon systems. The main research work is described as following:1. On the analysis of electric actuator system feature, the necessity of the drive system miniaturization is pointed out. The development process of semiconductor power device is analyzed. We predict that power device made by Si C material would be the first choice in power electronic domain. It provides a new idea for electric actuator system miniaturization. As one kind of switch, the characteristics of MOSFET, such as turn-on characteristics, turn-off characteristics and loss, are analyzed detailedly. The advantage of Si C MOSFET is given.2. The inverter working principle is discussed, based on three-phase full-controlled bridge topology structure. The main control method are sinusoidal pulse width modulation and space vector pulse width modulation. The working principle and the maximum inverter efficiency are introduced. Comparing the two kinds of control methods, we know that the space vector pulse width modulation inverter has higher efficiency. Combined with the characteristics of space vector pulse width modulation, the software realization process is given, including vector determination and turn-on time calculation of the power switching device.3. One design method of rare earth permanent magnet motor drive system is proposed,using Si C MOSFET construct three-phase inverter. The hardware system is built by DSP TMS320F2812. The whole hardware system contains the following parts: the smallest systems, driving isolation, gate drive capability enhancement, current acquisition, inverters and power source conversion. The basic design principles of the circuit for each module are discussed. Based on the designed hardware principle diagram, the circuit diagram and the PCB board diagram are given by Altium Designer software. The software is built on the control method of constant ratio between voltage and frequency of rare earth permanent magnet motor, combined with space vector pulse width modulation. The software flow charts including the main program and the interrupt service program are given. The software is carried out under the CCS development environment.5. The designed drive system has the following process: manufacture process, welding process, debugging process. On the basis of designed system, the features of switch circuits built by Si C MOSFET, Si MOSFET and Si IGBT, are tested. The results show that the switch circuit constructed by Si C MOSFET has advantage on the turn-on delay time, rise time and turn-off time. It can be much closer to the ideal state. Thus it help to achieve the excellent performance of the chopper control algorithm proposed based on the ideal state. For the goal of controlling rare earth permanent magnet motor speed, we test the performance of the inverter. The results show that the designed inverter can carry out inverter function better and get a good speed regulation precision about 99%.