Multiwinding Flyback Clamp Snubber for 10 kV IGCT with Reduced Voltage Stress on Clamp Recovery Diodes

About 10 kV integrated gate-commutated thyristor (IGCT) has the potential to push wind turbine systems to higher power and voltage ratings. Converters employing IGCTs need snubber and overvoltage protection circuit to limit the rate of current rise and peak overvoltage across IGCT during turn on and turn off state, respectively. The conventional resistor-capacitor-diode (RCD) snubber, which is used in such power converters, dissipates a significant amount of power. This article proposes an enhanced scheme of the flyback clamp snubber comprising a flyback transformer with multiwinding secondary wound on a magnetic core. The flyback snubber not only meets all of the IGCTs requirements during on and off-state but also significantly saves power. Unlike the basic concept of flyback clamp snubber, the new scheme has equal voltage stress across the clamp diodes which recover the stored energy of the di/dt snubber into dc-link capacitor. Simulation and experimental results of 10 kV IGCT with conventional RCD and flyback clamp snubbers turn out the benefit of the system.