Experimental evaluation of IGCT converters with reduced di/dt limiting inductance

Integrated gate commutated thyristor (IGCT) shows excellent potential in high-power converters owing to its advantages of low on-state voltage, low cost, and high reliability. However, a di/dt limiting inductor and a clamp circuit must be added to IGCT converters to protect the freewheeling diodes (FWD) from severe reverse recovery, leading to additional size and losses. So far, the di/dt is still limited to lkA/μs in most of the IGCT converters, even the maximum turn-off di/dt of up-to-date fast recovery diodes has already reached up to 5.3kA/μs. In this paper, the maximum di/dt of both IGCT and diode is studied. The current commutation process of the clamp circuit is analyzed. The switching losses of IGCT, diode and clamp circuit are tested at different di/dt from 1.1kA/μs to 19.4kA/μs. Results show that the switching losses of IGCT converters will be reduced by 40% with lower di/dt limiting inductance. A back-to-back power cycling test of two half-bridge IGCT converters at 2200V/1500A and 150Hz verifies the long-term reliability of IGCT converters at maximum di/dt of 5.2kA/μs.