Thyristor based bridge-type fault current limiter for fault current limiting capability enhancement

This study deals with a developed thyristor based bridge-type fault current limiter (TBFCL), in which the main fault current limiting function is relegated to a limiting circuit controlled by a silicon controlled rectifier (SCR). Since SCR is a reliable power electronic switch and can be found in high ratings, the proposed TBFCL can be utilised in higher ratings in comparison with other proposed BFCLs. The TBFCL limits fault current in two steps; (i) by a fully controlled DC reactor during transient fault interval (ii) by a SCR based current limiting circuit during steady state fault interval. The TBFCL has a bridge-type DC reactor controlled by an isolated gate bipolar transistor and a current limiting circuit in parallel with the bridge controlled by a thyristor. Upon fault occurrence, the DC reactor limits increasing rate of the fault current, while the generated over voltage activates auto-triggering control circuit of the SCRs. Therefore, the fault current is limited through the SCR current limiting path and the DC reactor path is interrupted. Analysis of the proposed TBFCL is presented in detail. Simulation and experimental results verify the performance of the TBFCL.