Modeling and Simulation of UHVDC Transmission Project Under Hierarchical Connection Mode to AC Grid

An ultra HVDC hierarchical connection mode was proposed by scholars in China to address the technical problems in multi-infeed HVDC system from the aspect of grid structure, but the control of UHVDC system with this kind of connection mode is not clear and needs to be further studied. In this paper, the control strategy of the system is discussed and designed. On this base, accurate models of AC system, converter transformer, AC/DC filter, converter, smoothing reactor and transmission line are built up in PSCAD/EMTDC software according to practical parameters based on Ximeng-Taizhou UHVDC transmission project which will use the new connection mode. The conclusion is that the control strategy designed for the AC-DC system in this paper is effective and simulation results of the model are in agreement with the actual operation characteristics. So the model can be used as a tool for further study.