Gate Commutated Turn-off Thyristor Research Articles

It is desirable that ac/dc converter for system interconnection (such as High Voltage Direct Current transmission system) should have following performance. (1) The converter does not fail to carry out commutation even when a voltage dip or distortion has broken out in the ac system. (2) The converter is able to send power from a healthy ac system even when another ac side has completely failed. (3) The converter is able to reduce generation of harmonics power in the network. It is necessary to improve characteristics of power semiconductor devices besides adoption of self-commutated ac/dc converter and development of control scheme. IGBT (Insulated Gate Bipolar Transistor), IEGT (Injection Enhanced Gate Transistor), GCT (Gate Commutated Turn off Thyristor) and Static Induction Thyristor (SITh) will be able to refine the characteristics. Especially SITh has high di/dt and dv/dt critical ratio and high switching characteristics. It is expected to apply SITh to power system in the future.From these background, 4.5kV-1kA SITh which consists of 70mm in diameter pellet with the planer gate structure has been developed. This SITh shows a normally-off characteristic because of a low concentration p-base layer under n-emitter, and has a pin-base structure. For lifetime control, electron irradiation and proton implantation were used. A 5kHz-frequency test in a chopper drive was achieved in condition of 2250V as a supply voltage and 270A as a rectangular on-state current. Adopting a hard drive operation, a snubberless turn-off drive of I000A as an anode current was also achieved.