IGBT Series Voltage-sharing Technology Of DC Hybrid Circuit Breaker

DC microgrid protection technology is one of the research hotspots in academia and industry,and hybrid DC circuit breaker is a key device for microgrid protection.In order to improve its breaking capacity,the series structure of power electronic devices is widely used in commutation branch.Insulated gate bipolar transistor(IGBT)is the most representative power electronic devices.Achieving IGBT series voltage balance is of great significance to the reliability of breaking.The dynamic voltage balance can not only improve the utilization of the device,but also prevent the device from being damaged due to overvoltage.Therefore,the IGBT series voltage sharing technology has significant research value.Firstly,starting from the IGBT device itself,the basic structure and working principle of the IGBT were elaborated in detail.The influence of the static characteristic parameters on the IGBT on-state operating condition,and the influence of the dynamic characteristic parameters on the transient operation of the IGBT were analyzed.The forward bias and reverse bias safe operation area of IGBT were specified.Device parameter difference,peripheral circuit difference and turn-off time difference leading to IGBT series voltage imbalance were analyzed.Secondly,the RCD snubber circuit was studied,and the influence of buffer resistance and buffer capacitance on the dynamic characteristics and voltage sharing characteristics of IGBT were obtained.The voltage sharing circuit can effectively reduce the rate of collector-emitter voltage.It also improves the problem of collector-emitter voltage imbalance,and plays a role in reducing turn-off losses and suppressing overvoltage.Through simulation and experimental verification,the best circuit parameters were finally obtained.Thirdly,the gate voltage sharing circuit was studied.Through the phased equivalent model and theoretical derivation,the relationship between the gate resistance and the dynamic characteristics and voltage sharing characteristics of the IGBT were analyzed.It was verified that switching the gate resistance can directly change the IGBT turn-off gate current,indirectly realize the control of the rate of collector-emitter voltage.By suppressing the rate of collector-emitter voltage of the IGBT with larger overvoltage,the problem of voltage imbalance can be improved,and the peak value of the overvoltage is suppressed to a certain extent.Finally,the hardware circuit design of the gate voltage sharing scheme was carried out.The parameter design of the voltage acquisition circuit,isolation circuit,power supply circuit,level conversion circuit,half-bridge drive circuit,and power amplifier circuit was completed.1.2kV collector-emitter voltage and 15 V gate voltage can be acquired.The gate voltage sharing circuit can turn on or off the IGBT with different gate resistor,and can switch the gate resistor in nanoseconds to complete the voltage sharing operation.The hardware design of the gate voltage sharing circuit provides a technical reference for the implementation of the voltage sharing scheme based on gate resistor switching.