Modeling And Simulation Of Hybrid-hVDC System Based On LCC And VSC

In recent years,LCC-HVDC of large capacity and long distance has been widely applied,but it needs a large amount of reactive power,and the power supply to passive network is prone to commutation failure.VSC-HVDC based on fully controlled devices can independently control active and reactive power,which can solve the problem of commutation failure,and connect passive network to power supply,but the cost of VSC-HVDC is much higher than LCC-HVDC.At this time,Hybrid-HVDC becomes the hotspot of scholars.Hybrid-HVDC integrates the advantages of LCC-HVDC and VSC-HVDC,and becomes the way to solve the problem of commutation failure and to transmit large capacity.Firstly,the thesis introduces basic principle of Hybrid-HVDC.The thesis describes the basic structure and working principle of LCC-HVDC and VSC-HVDC.Then,the thesis elaborates on the mathematical model of LCC-HVDC and the mathematical model of VSC-HVDC,and the mathematical models of HB-HVDC.The thesis illustrates the control method of Hybrid-HVDC and the coordinated control strategy of HB-HVDC.At the end,the thesis describes the modeling method of Hybrid-HVDC,and builds the PSCAD simulation model of rectifier,DC line and inverter and completes the modeling of Hybrid-HVDC.The thesis analyzes steady-state characteristics of HB-HVDC and the operating characteristics of single-phase grounding fault.The simulation results show that the Hybrid-HVDC system with complementary advantages of LCC and VSC has good steady-state characteristics,which verifies the feasibility of the control strategy and the fact that VSC in Hybrid-HVDC has stronger fault control and recovery capability than LCC.