Presenting a New Fault Current Limiter Structure to Reduce the Over-voltage of the DFIG DC Link in the Voltage Sag Condition

In this study a new type of fault current limiter is introduced. It has been named multi-functional capacitive fault current limiter (MCFCL). as a variable capacitor, its function is to control active power flow in normal conditions as well as improving the capability of low voltage rid-through (LVRT) in fault operating conditions. The new structure has been proposed based on the capacitive bridge-type fault current limiter (BFCL) and the RL-type fault current limiter (FCL), which is modified to enhance low-voltage ride-through capability. To assess the efficacy of proposed fault current limiter, the time domain simulations were executed in PSCAD/EMTDC software and its function is compared with the RL-type SSFCLs in normal and symmetrical or asymmetrical fault conditions. Also its efficacy has been evaluated in a fixed speed based wind farm. The result of simulations showed that the MCFCL is not only able to control the power flow in normal operating condition, but also improves the LVRT performance in fault operating condition in the wind farms.