Research On Application Characteristics Of Paralleled IGBT Modules

As a voltage controlled power device,IGBTs(Insulated Gate Bipolar Transistors)are widely used in the fields of rail transit,renewable energy and industrial transmission with the advantages of low on-state voltage,high switching speed,higher current tolerance,etc.With the development of semiconductor manufacturing technology,the power density of mainstream commercial IGBT modules has been significantly improved where the module power capacity can reach 6500V/1000 A or 4500V/3000 A that could basically meet the high-voltage and high-power applications.In some high-power or high-power density applications,the capacity of a single IGBT module is insufficient to satisfy the system design requirements.For these special applications,the parallel connection of power modules or device modules is generally adopted.The dynamic response of the system with paralleled device modules is better than that of the parallel connection of power modules,and it decrease the number of the components used for filter and energy storage which are necessary to power module paralleling.In addition,the parallel connection of switching device modules could reduce the cost of the power loop design with the increasing of system’s power density,and make the components of the power stack unit simple and easier to maintain.Furthermore,it is more economical in most cases to increase the current capacity of the system by paralleled IGBT modules.In the application of IGBT modules paralleling,the influence of inconsistence of the factors such as dynamic and static characteristics of the module itself,the power loop layout,and the parameters of driving circuit,heat dissipation layout and junction temperature changes on the static and dynamic current sharing characteristics could be suppressed,by optimizing the power loop characteristics and driver loop structure accompanied by the amplitude or delay adjustment of the gate driving voltage.As a consequence,the performance of each paralleled module could be fully played and the derating of the system output current would be reduced effectively in prevention of IGBT module’s premature aging or failure in which the reliability and stability of the system could be ensured.In this paper,the magnetic coupling characteristics on power loop and control characteristics of gate driving of paralleled IGBT modules.Firstly,the research analyzes the elements which influence static current sharing and dynamic current sharing of paralleled IGBT modules.The ststic current imbalance caused by the magnetic coupling effect on power loop.Combined with the equivalent circuit and electromagnetic field distribution,the construction and simulation of corresponding PSpice electrical model are carried out,and the static current sharing characteristics of paralleled IGBT modules under different power loop structures are compared.Furthermore,the mathematical relationship between the gate voltage,collector current and collector voltage during the turn-on and turn-off processes of IGBT module is analyzed.After deriving the amplitude-time function of the key phases that affect the current sharing characteristics during the turn-on and turn-off peocesses of paralleled IGBT modules,asynchronous gate signal driving method is proposed.A four-module paralleling PSpice simulation circuit was established to verify the effectiveness of the method in suppressing the dynamic current imbalance,and the improvement of the method on the dynamic current sharing is compared under different reference signal selection principles.At the end of the paper,the experimental platform for testing the current sharing characteristics of paralleled IGBT modules in parallel is constructed.The paralleling characteristics with four FF450R33TE3 IGBT modules are tested to verify the magnetic coupling characteristics on power loop.With asynchronous gate signal driving algorithm for current sharing control,the delays used in asynchronous gate driving compensation of four 2MBI200U4H-120 IGBT modules paralleling are set.Then the effectiveness of asynchronous gate signal driving method is verified by the double pulse test.Through the evaluation about the experimental data,the analysis and control methods for improving the current sharing of paralleled IGBT modules proposed in this paper are proved to be correct and effective.