Analysis and Experiment of Stress Boundary and Regulation Method of RB-IGCT Under Snubber Component Fault in H-LCC

The hybrid line commutated converter (H-LCC) has been shown to mitigate commutation failure utilizing the controllable turnoff ability of reverse blocking integrated gate commutated thyristor (RB-IGCT), however, RB-IGCT active turnoff stress will become critical caused by snubber components failure. To improve reliability of H-LCC, a novel topology with high tolerance snubber component parameter difference is proposed. This article analyzes RB-IGCT turnoff process and reveal interaction relation between snubber components and RB-IGCT. Then active turnoff process simulations with different snubber circuit parameters under original and novel topology are conducted to reveal the impact of snubber resistor and snubber capacitor on the voltage deviation from design value of RB-IGCT, and then failure mechanism of RB-IGCT stemming from high voltage, ending at insufficient reversing bias voltage of J3 raised by dynamic avalanche is deciphered. Finally, experimental tests suitable for H-LCC of original and novel topology are conducted, results show that proposed method is insensitive to snubber parameters change.