Influence Pattern of VSC-HVDC Grid to the Power Grid on the Transient Stability

High voltage direct current transmission with voltage source converter(VSC-HVDC) grid-connected is an important trend in the future development of power grid. It is of great significance to reveal the influence of VSC-HVDC grid-connected on the transient stability of power grid. The external power characteristics of VSC-HVDC are equivalent to time-varying ground admittance. Based on the extended equal area criterion (EEAC), the influence of VSC-HVDC grid-connected admittance on the self-admittance and mutual admittance of synchronous generator internal potential node is studied, the quantitative relationship between the VSC-HVDC grid-connected admittance and the change of transient power angle stability margin is deduced. Based on this, the influence law of the active and reactive power on the transient stability of the power grid is quantitatively analyzed. Finally, the correctness of the conclusion is verified by simulation.