Key technologies on series connection of insulated gate bipolar transistors

In order to achieve the series connection of insulated gate bipolar transistors (IGBTs), resistor-capacitor-diode (RCD) snubber circuit, which was chosen for active voltage sharing, was analyzed by mathematical methods, then the RCD snubber circuit parameters were modeled and proved by PSpice simulations. Based on optical fiber transmission and M57962L, the drive circuit and fault feedback circuit controlled by digital signal processor (DSP) were designed to drive 32 series connected IGBTs and for overcurrent and short circuit protection. The maximum break-over time in 32 IGBTs was 90 ns, while failure protection completion time was 6 s. Eight independent isolated sources were designed for the isolation voltageof 50 kV. Based on the above research achievements, the 32 IGBTs series connected circuit can work safely under the voltage of 20 kV.