Bus protection in systems with inverter interfaced renewables using composite sequence currents

Power systems are experiencing noticeable changes in operation with the integration of a large number renewable sources, which are generally connected to the grid through inverters. With significant modulation in voltage and current during fault by the embedded controllers in the inverters, available grid protection schemes are vulnerable. The theoretical analysis and simulated case studies reveal the influencing factors on the malfunction of the conventional busbar differential protection while connected to an inverter based resource.
This paper proposes a differential protection method for the busbar, connecting inverter based resources to the grid, based on composite sequence currents. The performance of the proposed method is immune to the variations due to control action in the inverter based resource and change in grid codes. The IEEE 9-bus system interconnecting a PV plant is used to evaluate the proposed method where the comparative assessment reveals its superiority.