Modeling of DC asymmetrical faults in bipolar HVDC links with metallic return

This work proposes a compact and flexible dynamic model of a bipolar HVDC link with metallic return, suitable for simulation of power systems. The model is formulated compactly using only two matrix equations and is capable of simulating different types of faults, including pole-to-ground, pole-to-neutral and pole-to-pole faults. The inclusion of the dynamic equations of the neutral cable enables accurate asymmetric perturbation dynamic studies. The proposed model has been included as a module in a software framework which is aimed for dynamic simulation studies in AC/DC systems. Results demonstrate the model’s functionality and capability to simulate various fault types, including asymmetric faults, where the neutral cable plays a pivotal role. Key words. HVDC transmission, metallic return, AC/DC power systems, fault modelling, time-domain simulation.