Characteristics analysis and loss optimization of the turn-on clamp circuit for IGCT based DC transformer

Integrated Gate Commutated Thyristors (IGCT) has a natural advantage in high voltage and large capacity power electronic equipment due to its high current processing capability. However, due to the positive feedback in the IGCT turn on process, the turn-on clamp circuit must be added to limit the switching speed which reduces system efficiency. This paper firstly introduces the working principle of opening clamp circuit. Secondly, the bus current in Modular Multilevel Converter (MMC) and Double Active Bridge (DAB) are compared, and pointed that the backflow power of DAB will significantly increase the loss of clamped circuit. In order to reduce the loss if clamped circuit and further improve the efficiency of IGCT-DAB, reducing the inductance and buffer capacitor in parallel with the IGCT were proposed, and their feasibility was analyzed. Finally, a DAB prototype of 1.5kV/3MW was constructed in MATLAB/Simulink to verify the correctness of the theory.