Bridge-type fault current limiter for asymmetric fault ride-through capacity enhancement of doubly fed induction machine based wind generator

Doubly fed induction machine (DFIM) based wind generators are vulnerable to the grid faults, as their stator windings are directly connected to the grid. Besides the symmetrical faults, asymmetrical faults are also problematic to DFIM, as asymmetrical faults put turbine generator system into high electromechanical stress leading to instability and mechanical damage. There are also requirements to abide by grid codes by having fault ride through (FRT) capability. A bridge-type fault current limiter (BFCL) is proposed to enhance the asymmetrical FRT capability of DFIM based wind generator. A double-line-to-ground (2LG), line-to-line (LL) and single-line-to-ground (1LG) faults were applied to one of the double circuit transmission lines of the test system to investigate the asymmetrical FRT capability enhancement. Simulations were carried out in Matlab/Simulink environment. To demonstrate the effectiveness of the proposed BFCL, its performance is compared with that of the series dynamic braking resistor (SDBR). Graphical and numerical results obtained from simulations show that the BFCL is a very effective device to enhance the asymmetrical FRT capability. Moreover, the BFCL works better than the SDBR in every aspect.