A Novel Multistage Gate Unit of Integrated Gate Commutated Thyristor

Integrated gate commutated thyristor is developing toward larger size and higher turn-OFF current, so its gate unit is also required to have larger turn-OFF capability and higher commutation speed. Limited by the parasitic impedance and the 20-V constant gate voltage, the conventional gate unit is approaching the limit of its commutation capacity. A novel multistage gate unit concept and its control method are proposed in this letter. Through the coordinate action and elaborate design of circuit parameters of multiple turn-OFF branches, the gate voltage at different periods can be adjusted, to achieve ultrafast commutation while avoiding the risk of gate breakdown. Based on the pulse test of a 4-in prototype, half commutation time was realized under 5-kA turn-OFF current compared with the conventional gate unit. With the help of cathode current measurement, different operating modes can be programmed to effectively avoid gate breakdown risk.