Electromechanical Transient Modeling And Connecting Mode Of HVDC

For sheer efficiency, electromechanical transient simulation softwares are widely used in AC-DC hybrid power grid research. Yet the demand of AC/DC research is still falls short of what is neededbecause of the limited categories and encapsulation of the HVDC models in these softwares. From another perspective, the study of voltage stability issue of multi- infeed HVDC(MIDC) grid receiving-endin the case of large disturbancehas been a research hightlight in recent years:one of the solution is improving the support strength of receiving end grid, however, that would lead to short-circuit current over-limitation problems while faults applied on receiving end grid. Therefore, MTDC, or connecting the positive and negative poles of conventional HVDC into different substation comes come into use, which could increase the electrical distance as well as decrease the interaction effect of HVDC subsystems.In this dissertation, several HVDC system are built by user-defined function of PSS/E, and the connecting mode of inverters is studied. First, this research detailed descripted the userdefined function of PSS/E by whose modeling mechanism, environment configuration, process control, data demand and modeling process. And the modeling method is validated by the simulations of user-defined excitation system and SVC.Then, this research builts two HVDC system models and a MTDC system modelin PSS、E referenced byCIGRE HVDC and YunGuang HVDC system. By this way, not only the electromechanical transient HVDC modeling method is brought into the open, but also a practice platform are built for operational experience. In addition, aiming at the fault characteristics of HVDC model in electromechanical transient simulation unable to correspond accurately with the ones in electromagnetic transients simulation, the factors that give rise to the inaccuracy have been evaluated, this research presents an improved electromechanical transient HVDC modeling method, the simulation results validates the correctness of this method.Finally, based on user-defined HVDC models, this dissertationstudies the effects of HVDC connecting mode on transient voltage stability of receciving end grid. The results indicates that when the HVDC transmitting power and DC voltage are equivalent, and inverters locating place are same, MTDC system gives the best performance on voltage restoration after large disturbance applied on receving end gird.