AC Drive Side Ground Fault Location for DC/AC Systems Based on AC Phases and Grounding Resistor Voltages

Power converters are essential for process optimization and electric drives control. However, the presence of both dc and ac currents in the same circuit makes the diagnosis and protection of this type of systems difficult. For this reason, a new ground fault location method for the controlled ac drive side of a dc-ac system is presented in this article. It is based on a grounding resistor placed at the midpoint of the dc bus, where its voltage is measured simultaneously with the ac drive side phase-neutral voltages.Applying a phasor operated equation, the faulty phase can be detected by angle comparison. Furthermore, an estimation of the fault location can be obtained. To verify the method, numerous simulations have been performed. The results show certain inaccuracies when the fault is close to the neutral of the system, which is inconvenient since the phasor equation requires precise values. In contrast, the ground arc resistance is not needed in the fault location process. The effectiveness of the method has been also corroborated through experimental tests on a 140 kW power converter, making the ground fault diagnosis in dc-ac systems practical and useful.