Electromagnetic Transient Simulation Analysis of Faults of Hybrid Cascaded UHVDC Transmission System

The LCC converter of the hybrid cascaded UHVDC transmission system studied in this paper is used for the rectifier side, and the LCC converter and VSC converter are hybrid cascaded for the inverter side. Firstly, the topological structure and mathematical model of the model are introduced. Secondly, the control strategy of the system is introduced, including control strategies for LCC converter and VSC converter. Finally, the simulation research of different models under different types of faults in PSCAD / EMTDC is focused on. By comparing the fault recovery characteristics of LCC-LCC transmission model, LCC-VSC transmission model and hybrid cascaded transmission model under typical AC faults, the advantages of strong fault recovery characteristics of hybrid cascaded transmission model are reflected. Through the simulation analysis of the DC line fault and AC fault of the hybrid cascaded transmission model, it is concluded that the system has all the advantages of mature LCC technology, low cost and good VSC control performance. At the same time, the shortcomings of the system in dealing with specific faults are pointed out, and measures should be taken to deal with them.