| As a kind of semiconductor switch,the thyristor can withstand high voltage,conduct large current and can be easy to be controlled.It has wide applications in pulsed power and power systems.However,with the continuous development of pulsed power technology,higher performance of the thyristor discharging switch is needed.Not only it is necessary to improve the turn-on speed and turn-on synchronization of the series thyristor,to enhance the stability of the voltage equalization protection circuit,but also to reduce the negative influence of the thyristor's own parameters on its system.In order to improve the turn-on synchronization and turn-on speed of the series thyristor,the triggering method of the cable passing through the coaxially distributed toroidal transformer was adopted,and the device selection,parameter selection and parameter verification of the toroidal transformer in the high frequency pulse application scenario were analyzed.The integrated amplification gate structure and the application of strong trigger drive circuit are two ways to improve the thyristor turn-on speed,and one of the strong trigger drive methods was deeply studied.A strong trigger circuit structure that the voltage doubling rectifier charging circuit is cascaded with an improved third-order discharging circuit was proposed,the analysis of the circuit showed that the proposed structure could improve the rise rate of the drive current,improve turn-on synchronization,and enhance the ability of the circuit to resist electromagnetic interference.The factor that will affect the stability of the drive circuit was analyzed and the protection circuits for the cable and the MOSFET switch were designed.The device selection,prototype development and related experiments were carried out.The experimental results showed that the peak value of the drive current generated by the proposed circuit structure could reach 203 A,the rising time was less than 4?s,and the drive current transmitted to the secondary side through the coaxial toroidal transformer could promote the turn-on speed and turn-on synchronization of the series thyristor.In order to improve the stability of the series thyristor voltage equalization protection circuit,the problem of having large parameter margin and even having no device to choose caused by the ideal turn-on model which only considers the difference of the delay time of the series thyristor in the open progress was analyzed.A segmented linear model was established to guide the voltage balance design in the open stage.The drawback that current rate is discontinuous in the peak current position of the exponential reverse recovery current model and the shortcoming that the parameter is hard to extract of the hyperbolic tangent reverse recovery current model were analyzed respectively.A sinewave reverse recovery current model whose amplitude decays exponentially was adopted to guide the voltage equalization design in the reverse recovery stage.The analysis showed that the RCD voltage balance circuit could protect the thyristor more effectively than the RC voltage balance circuit in the application scenarios of high voltage,high current,and high current rise rate.When the difference between the different thyristors is large,the RCD voltage balance circuit can no longer make the thyristor work in safety,the method of paralleling varistor was proposed to further prevent the single thyristor from being damaged by overvoltage.On the basis of analyzing the static characteristics,turn-on characteristics and reverse recovery characteristics of thyristors,the parameter design,device selection,simulation analysis and prototype development were done.Simulation and experimental results showed that the voltage balance circuit with RCD circuit and varistor could improve the stability of the thyristor switch in high current rise rate condition.In order to reduce the negative influence of the thyristor's own parameters on the system where the thyristor works,the abrupt change of voltage caused by the conduction voltage of the thyristor and the anti-parallel diode when the magnet current was in commutation stage was analyzed and the interference to the magnetization measurement was also explored.The method of exchanging the dynamic voltage balance circuit and adding the external compensation source were proposed respectively to eliminate the abrupt change of voltage across the magnet in the magnetization power supply.Simulation results showed that these two methods could weaken the abrupt change of voltage. |
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