Study On Dynamic Interaction Between LCC HVDC And Synchronous Machine And Its Impact On Electromechanical Oscillation

Power system is a complicated and high-dimensional system,whose security and stability matter a lot.In traditional power system which is dominated by traditional electromagnetic devices like synchronous machine(SM),the electromechanical oscillation is considered to be determined by the rotor motion of SM,and is a phenomenon caused by the energy exchange and relative power swing among rotor motions of SMs.However,with the high penetration of semiconductor based flexible power conversion devices like line-commutated converter(LCC)high-voltage direct current(HVDC)transmission device,these power electronic devices interact deeply with tradition electromagnetic devices like SM,and influence profoundly the oscillation mechanism and damping characteristic of electromechanical oscillation.Therefore,it is of great theoretical value and urgent practical need to study the dynamic interaction between LCC HVDC and SM along with its impact on electromechanical oscillation.This dissertation build the original mathematical model,small signal model and magnitude/phase motion model of rectifier and inverter of LCC HVDC,and verify its validation by comparing with detailed model in MATLAB,which provide a generalized method and physical insight to model various power electronic devices.Moreover,this dissertation build the magnitude/phase motion model of classical four-machine two-area power system which is composed of LCC HVDC,SM,and AC grid.Using the methods of time-domain simulation,eigenvalue analysis and damping torque analysis,this dissertation firstly analyze and summarize the impact on the damping and frequency of inter-area mode and local mode of electromechanical oscillation when power distribution and operation mode vary.Then,this dissertation analyze and verify the accurate control of damping of inter-area mode of electromechanical oscillation by DC power modulation.