Study On Control Strategy And Simulation Of Three-level VSC-HVDC System

With the development of high power turn-off power electronic components and PWMtechnique，Voltage Source Converter based High Voltage Direct Current(VSC-HVDC) hasbeen realized successfully in the world, and it is superior to the traditional HVDC. Because ofusing full controlled components，the VSC-HVDC system not only can ensure the balancingof active power transmission，but also adjust reactive power independently. It also can supplypower to weak AC system and passive network，which made it have the broad applicationprospects.The mathematical model and working principle for diode Neutral-Point-Clamped (NPC)three-level VSC based HVDC system is presented in this thesis. Based on this model，thefundamental principles of the active and reactive power control has been also presented，andthe method of a improvementcontrol system based on traditional double closed loop controlsystem has been stated. MATLAB simulation result plots and the analysis are given. Thispractical operation shows that this improvement controller has good control effect and thesystem gets high response speed and quite good stability.