A Dynamic Multi-Cell FCL to Improve the Fault Ride through Capability of DFIG-Based Wind Farms

Endowing wind farms (WFs) with fault ride through (FRT) capability is crucial to their continuous availability under various operating conditions. This paper proposes a dynamic adaptive multi-cell fault current limiter (MCFCL) topology to enhance the FRT capability of grid connected WFs. The proposed MCFCL consists of one transient cell (TC) and multi resistive cells (RCs) directly connected to the grid's high voltage without using any series injection transformers nor any series connection of semiconductor switches. The transient cell of the MCFCL includes two transient limiting reactors (TLRs) to mitigate the transient fault current and limit the rate of change of the currents of the semiconductor switches during fault occurrence. The number of RCs in the MCFCL is determined based on voltage sag level. These latter are inserted in the fault path to provide an adaptive voltage sag compensation mechanism according to the voltage sag level. Assessment of the MCFCL under various sag conditions, showed that the MCFCL is able to effectively compensate for a wide range of voltage sags without any over voltage at the WF's terminal. Comparison analysis with the conventional single-cell bridge-type FCL (SBFCL) showed the superior performance of the proposed MCFCL.