Optimal design of a medium voltage hybrid fault current limiter

The connection of distributed generation increases the short circuit power which in turn might exceed the ratings of the installed circuit breakers. A solution is to limit the available short circuit power by increasing the grid impedance, but since there is a constant strive for lower losses and higher power transfer capabilities, this is not desired. The application of a fault current limiter (FCL) that can limit the current before the first peak enables a power system with high short circuit power and low short circuit current. This can increase the stability of the grid and reduce the requirements of other equipment. This work presents a simulation model to be used as an aid in the design of a hybrid FCL for a 12 kV AC system. The proposed model combines a transient analysis circuit model with an optimization module to obtain multiple sets of possible design parameters. The design is not straight forward since there is a trade-off between several of the design parameters.