Hardware-in-the-loop Tests on Distance Protection Considering VSC Fault-ride-through Control Strategies

The short-circuit response of a voltage source converter (VSC) can vary from each other significantly with different control strategies. This study investigates the performance of distance protection under unbalanced faults considering two control strategies during fault-ride-through using hardware-in-the-loop tests. Variations on fault type, converter current limit, fault resistance and pre-fault power flow conditions are also examined. The tests reveal that the error in measured impedance caused by fault resistance will be enlarged in a converter-dominated power system. The first control strategy tends to cause overreach problem while the second can raise both overreach and underreach problems. The indeterminacy associated with the second strategy is jointly affected by control parameters, converter current limit, fault resistance and pre-fault power flow conditions. The findings of this study can help to stipulate grid requirements under unbalanced faults.