A Novel Short-Circuit Fault Current Calculation Method For DC Grids

in recent years, flexible DC grids has developed rapidly and the Short-circuit protection is the main reason limiting its development. The calculation of fault short circuit is of great significance for the research of DC grid short circuit fault protection. There are virtual nodes in the equivalent circuits of some DC grids, which will cause the number of state equations of the DC grid and the number of state variables to be different. The algorithm proposed in this paper eliminates virtual nodes through a novel star-mesh network transformation and simplifies the calculation method of fault current. The proposed method is verified to be accurate and time-saving by comparison with the simulation results of electromagnetic transient (EMT) on PSCAD. This method can be applied to all kinds of VSC-HVDC network (ring, radial, and meshed topologies) and different types of short-circuit faults (pole-to-pole and pole-to-ground.).