Study Of Switching Control Strategy Of Si IGBT/SiC MOSFET Hybrid Switch And Its Application

In recent years,the complex and special applications such as rail transit,aerospace,military and nuclear power have put forward more stringent requirements for inverter in terms of power density,efficiency,capacity stability and reliability.However,the adoption of the pure Si IGBT or Si CMOSFET is difficult to meet these strict requirements,which severely limits the application technology of the single power devices and the further development of related industries.To meet the application requirements of the high efficiency,high power density,large capacity and high reliability of the inverter,this paper combined with the large capacity Si CMOSFET and the small capacity Si IGBT to propose the Si/SiC hybrid switch.In this paper,the Si/SiC hybrid switch is taken as the core,and the inverter application is taken as the background.The corresponding optimization and control methods are designed for the power loss,EMI noise and redundancy fault-tolerant characteristics of this hybrid switch.Then,the parallel control technology and the energy management strategy are combined to provide technical and theoretical support for the development and engineering applications of the high performance and high reliability of the modular inverter system.The innovation points of this paper are shown in the following.(1)An adaptive loss optimization method for the Si/SiC hybrid switch is proposed by using a gray wolf algorithm and designing the fitness function.A power loss model of the Si/SiC hybrid switch based on the physical characteristics of the device is established,and the relationship between its internal delay time and its own power loss is studied.Aiming at the problem that the optimal delay time is difficult to be obtained,this paper selects the gray wolf algorithm with excellent performance from the natural heuristic algorithm and combines with the fitness function reflecting the average power loss of the inverter.Then,an adaptive loss optimization method suitable for the Si/SiC hybrid switch is proposed.Compared with the fixed delay time,the proposed adaptive loss optimization method can effectively reduce the power loss by more than 6%.(2)This paper studies the EMI noise characteristics of the Si/SiC hybrid switch under different driving patterns,analyzes the switching frequency curve under the background of inverter application,and proposes an EMI noise suppression strategy suitable for the Si/SiC hybrid switch.Firstly,the high-frequency model of boost converter based on the Si/SiC hybrid switch is established,and the conducted EMI characteristics of the Si/SiC hybrid switch are analyzed to provides the theoretical basis for the design of the optimal drive resistance and EMI noise suppression strategy.Then,aiming at the serious EMI noise problem caused by the traditional control strategy,the EMI noise suppression strategy including the variable switching pattern and variable switching frequency strategy is designed.Without reducing the performance of the inverter,the conducted EMI noise of the inverter can be effectively reduced in the frequency range of 150kHz ～30 MHz,and the radiated EMI noise is reduced indirectly in the frequency range of 30MHz ～ 1GHz.(3)After analyzing the fault tolerance characteristics of the Si/SiC hybrid switch,a fault detection method is designed,and a redundancy fault-tolerant control strategy suitable for the Si/SiC hybrid switch is proposed.When the open circuit fault of the Si/SiC hybrid switch is happened,the excessive conduction current and pulse width change will affect the operation performance and reliability of the inverter,which greatly limits the operation range of the Si/SiC hybrid switch.In order to effectively solve this problem,the operation characteristics of the Si/SiC hybrid switch after the faults are analyzed to predict the performance of the inverter.Secondly,the fault detection method of the Si/SiC hybrid switch is designed.Finally,a redundancy faulttolerant control strategy combining the multiple control methods is proposed to improve the waveform quality,operation efficiency,and reliability of the inverter.(4)Combined with the above optimization and control methods,a modular inverter system based on the Si/SiC hybrid switch is developed to improve its performance and availability before and after fault.Firstly,the adaptive loss optimization method,EMI noise suppression strategy,and fault-tolerant control strategy are combined into the modular inverter system,and the particle coding process in the adaptive loss optimization method is modified.Then,the virtual synchronous generator control strategy based on virtual impedance and the appropriate energy management strategy are also applied to improve the efficiency and EMC capability of the system in normal operation.The proposed scheme can also prevent the power quality,efficiency,and availability of the system to be declined significantly after the failure.The experiment shows that the modular inverter system can operate stably and reliably.After the fault occurs,the inverter unit efficiency is higher than 98%,the system common point voltage harmonic is less than 1.3%,and the junction temperature of each power device is always less than 95°C.