Protection of systems containing IBR from asymmetrical ground faults using zero sequence current with hardware implementation on FPGA

Abstract

The addition of inverter-based generation to the power system complicates protective relaying in several ways: the magnitude of the fault current will be altered based upon the location of the fault relative to the inverter-based resource, and the response to a fault will be different than traditional generation. The relatively low fault current of inverter-based resources presents difficulties in differentiating faults from increased loads. Additionally negative sequence relays may fail in the presence of IBR's due to the negligible negative sequence current produced by the IBR during a fault. This paper presents a novel method to allow the sensitive sub-cycle detection, and determination of the relative location, of asymmetrical ground in systems containing inverter-based resources through phasor analysis of zero sequence current. Least Error Squares Estimation is applied to the fault currents to improve the detection time of these faults, with low computational overheard for hardware implementation. Hardware implementation of the protection scheme on an Intel Cyclone IV-E FPGA is completed and correct operation of the scheme is verified for the raw samples, as well as five and seven sample LES phasor estimations. Hardware testing is compared to the EMT output to confirm the results.