The Model and Parameters Based on the Operation Mode of a 500kV Multi-terminal Flexible DC Power Grid

Abstract

The operating conditions of 500kV Zhangjiakou-Beijing Demonstration Project at all operation modes were studied regarding a multi-terminal flexible DC system with DC switches and a true bipolar wiring method. Based on the actual AC-DC hybrid method, this paper concluded 34 kinds of N-1 operation modes for keeping the system stable, simulated the multi-level converter valve (MMC) bank by using RTDS small-step elements, adopted an ideal voltage balancing method for the treatment of sub-units and established a MCC system simulating structure in compliance with the site.  The operation modes of the system were simulated by selecting the parameters which are consistent with the line, using such parameters as the actual configurations and parameters of key elements such as the converter transformer, filter, bridge arm reactor, converter, etc. adopted in the project, and establishing a flexible DC control system with a layered structure.  According to the result of the simulation, the corresponding modes of the system were provided and references were given for the feasibility study and implementation of the project.