Application Of 6.5kV RC-IGBT In Four-quadrant Converter

Four-quadrant converters used in the vehicle have higher requirements on the power density and the reliability.Compared with the conventional IGBT module,Reverse Conducting-IGBT(RC-IGBT)of the same package has lower thermal resistance and higher current tolerance.By using the gate of RC-IGBT to control the desaturation characteristic of the diode,the diode conduction loss and the reverse recovery loss can be reduced.Taking the traction drive system of rail transit as the research background,RC-IGBT is applied to the four quadrant traction converter,which effectively improves the power density and reliability of the system while reducing the loss of converter system.This thesis focuses on the analysis of the RC-IGBT structure and control characteristics,the control strategy of four quadrant converter and the loss analysis,and other key technologies.Firstly,from the research background of the device,it is very important to analyze the RC-IGBT.The low on-state voltage drop and small reverse recovery current of the RC-IGBT are researched.The gate pulse saturation control of RC-IGBT integrated diode is proposed.Taking half-bridge circuit as an example,the principle of applying desaturation pulse on RC-IGBT is given.Through application of 6.5kV RC-IGBT to four-quadrant converter,the control method of RC-IGBT four-quadrant converter is mainly studied.The working process of RC-IGBT four-quadrant converter is analyzed.Based on conventional predictive current control and judging the size and direction of the input current,the current threshold desaturation control of the RC-IGBT four-quadrant converter is proposed.The relationship between the input current and the system loss is established,and the loss threshold desaturation control is proposed.Secondly,the calculation method of RC-IGBT four-quadrant converter loss is proposed.Comparing the losses of RC-IGBT four-quadrant converter and the traditional four-quadrant converter by simulation waveforms,device data sheets and double-pulse test data.By drawing three-dimensional diagrams of the total losses of the converter system under different current thresholds and different load currents,the best working point of the converter is obtained.Thirdly,the simulink model of RC-IGBT four-quadrant converter is established.By comparing the operation characteristics of RC-IGBT four-quadrant converter under current threshold desaturation control and four-quadrant converter controlled under conventional predictive current control,the improved predictive current control is proved.The experimental platform of RC-IGBT four-quadrant converter was built,including the hardware parameters calculation of RC-IGBT four-quadrant converter,the preparation of DSP predictive current control algorithm and the CPLD desaturation control algorithm.Finally,the experiment was conducted and the experimental waveform was analyzed.This thesis presents the feasibility of applying threshold current desaturation control of RC-IGBT four-quadrant converter.