Study On 10kV Solid State Transfer Switch(SSTS)

With the rapid development of China’s economy and science and technology,a growing number of voltage-sensitive loads are put into use,such as precision instrument manufacturing process,automatic control equipment of continuous generation process,etc.The production technology and electricity equipment for power supply system of power quality put forward higher requirements;At the same time,a large number of impact loads and nonlinear loads are put into use,which seriously pollute the power quality of the power supply system.At present,voltage sag and short time outage have become the main important problems of power quality.In order to solve this problem,the static reactive power compensator(SVC),uninterruptible power supply(UPS),dynamic reactive power restorer(DVR),solid state transfer switch(SSTS)and other devices have been proposed at home and abroad to solve the problem of voltage sag and short time outage.Solid state transfer switch is the most economical and effective means to solve the problem of voltage sag and short time outage.Thyristor valve body is the core component of solid state transfer switch,the performance of the thyristor valve body will directly affect the operation of the whole solid state transfer switch,in the case of system failure,how to ensure that the solid state transfer switch thyristor valve body can conduct the switch accurately is particularly important.Ensure the performance of the thyristor valve body and its trigger module to ensure the normal operation of the solid state transfer switch.The design of the valve body and its trigger control unit for solid state transfer switch are mainly studied in this paper.In this paper,a hybrid solid state switch composed of the fast mechanical switch in parallel with the thyristor valve body is studied,based on the structure and working principle of solid state transfer switch and the switching strategy analysis,the influence factors of the switching of the solid state switch are analyzed,and the thyristor valve body of the 10 k V solid state switch is designed,the dynamic and static voltage equalizing circuit and overvoltage protection circuit are designed for the thyristor valve body.Thyristor trigger of solid state transfer switch is also a key problem.Photoelectric trigger is selected in the existing three trigger modes of thyristor: electromagnetic trigger,optical direct trigger and photoelectric trigger.A kind of solid state based on the photoelectric trigger mode switch trigger control unit(TCU)was designed,the trigger control unit includes logic circuits,du/dt protection circuit,voltage detection circuit,over voltage protection circuit,pulse amplification circuit,etc.,A new overvoltage protection circuit is designed.Compared with the traditional BOD overvoltage protection circuit,the designed overvoltage protection circuit in this paper has the advantages of simple structure and stable action.Hybrid solid state transfer switch at the ends of the thyristor voltage current in normal working conditions are close to zero,the traditional RC,PT take energy can not meet the solid state transfer switch of the thyristor gate trigger power requirements,a new kind of high frequency pulse takes energy circuit is designed,which has strong anti-interference ability,stable output,the advantages of good to power a thyristor trigger control unit.finally,the experiment of thyristor trigger platform is built,which verifies the correctness of the trigger control unit designed by the solid state transfer switch,the trigger control unit can monitor the two ends of the thyristor while touching the thyristor.The trigger control unit can also be used in other applications of series thyristor valve body.