Improving fault ride-through of three phase voltage source inverter during symmetrical fault using DC link fault current limiter

The majority of distributed generation (DG) units utilize three phase voltage source inverter (VSI) to exchange electric power with the utility grid. The VSI employs semiconductor devices (SDs) with limited current withstand capabilities which are very vulnerable during grid faults. However, to ensure a secure and reliable operation of power systems at high penetration level of the DGs, most of the new grid codes worldwide require that the VSIs must have fault ridethrough (FRT) capability. This paper presents a DC link fault current limiter (DLFCL) based VSI FRT scheme to improve its FRT capability. In the proposed scheme, the DLFCL is connected in series with the DC side of the VSI to limit the output current during symmetrical grid fault. The DLFCL does not have considerable effect on the VSI performance during the normal operation, whereas it limits the output current in all phases to the safe area operation of the SDs of the inverter. The effectiveness of the proposed scheme is validated through the simulation studies in PSCAD/EMTDC software.