Voltage sag compensation of point of common coupling for low voltage ride-through enhancment of inverter interfaced DG using bridge type FCL

Fully converter wind turbines and solar power utilise an inverter to connect to grid. The inverters are vulnerable to voltage sag in their terminal due to its damaging effect on semiconductor self-turnoff switches. In this paper, a bridge-type fault current limiter (B-FCL) is proposed for low voltage ridethrough (LVRT) of the inverters during different types of fault with simple control system. The proposed B-FCL is capable to compensate the voltage sag in point of common coupling (PCC) and makes a safe condition not only for the inverter but also for any equipment which has been connected to the PCC in the power system. The B-FCL does not affect the normal operation of the inverter. Whenever the fault happens, a limiting resistor enters to the line current pass and decreases the fault current. As a result, the voltage sag on the PCC is mitigated due to limiting the fault current. The proposed B-FCL improves LVRT capability of the inverter, which does not require to changing its control method to ride through the low voltage. Furthermore, the DC input voltage of the inverter will not increase due to consuming the excessive active power by the limiting resistance of the B-FCL. PSCAD/EMTDC software is utilised to show the appropriate performance of the B-FCL during the symmetrical and asymmetrical grid faults through simulation results.