Multi-resistor BFCL for FRT capability improvement of DFIG-based wind farm

Abstract

Grid connection of wind farms (WFs) results in increment of short circuit level and decrement of fault ride-through (FRT) capability under fault conditions. Application of bridge-type fault current limiter (BFCL) was recognised as a promising and cost effective solution to cope with these problems. However, full resistor insertion of the conventional BFCL provides high transient overvoltage at the terminal of wind generator under low voltage sag condition, which can lead to failure operation of wind generator in despite of FRT requirement. This study presents a voltage adaptive multi-resistor BFCL (MRBFCL) to solve these problems for wide voltage sag levels. According to the depth of voltage sag level at the grid coupling point voltage, the MRBFCL inserts an appropriate combinational of resistors to compensate voltage sag level at acceptable level. To verify the efficiency of the proposed MRBFCL, time domain simulations were performed in PSCAD/EMTDC software under three different voltage sag levels. Also, the MRBFCL performance is compared with the conventional single-resistor BFCL. Simulation results reveal that the MRBFCL effectively enhance the FRT performance of doubly-fed induction generator (DFIG)-based WFs under wide range of voltage sag level and alleviate over voltage for low voltage sag conditions.