Analysis on the Analytical Model of DC Fault for the Practical Pseudo-Bipolar Flexible HVDC System

In order to correctly reflect the change of the arm current during the pole-to-pole fault in the pseudo-bipolar back-to-back DC grid, a multi-stage analytic model of pole-to-pole fault is established, which is divided into three stages: the pre-blocking stage of the converter after the fault, the pre-tripping stage of the circuit breaker after the converter is blocked, and the stage after the circuit breaker trips. A three-stage circuit model is established accordingly, and the analytical expression or analytical equation of the arm current of each phase after the fault is derived. Simulation results have validated the accuracy of the analytical model.