Voltage Stability Analysis Of UHV Access Hebei Southern Power Grid

Hebei Southern Power Grid,an important receiving part of the North China Power Grid,has the responsibility to transfer electric power from Shanxi to Beijing-Tianjin-Tangshan and Shandong power grid.With the increase of components and loads and the access of UHV AC/DC,the grid's voltage stability becomes more and more serious,and needs to be analyzed urgently.According to relevant power industry standards,this paper studied the static voltage stability under small disturbance and the transient voltage stability under large disturbance of the grid.PV and QV curve are two useful tools of static voltage stability analysis,but they cannot be calculated perfectly by power flow program of PSD-BPA.According to grid's reality and program's functions,a static voltage stability analysis method based on PV and QV curves which is suitable for Hebei Southern Power Grid are introduced.Then,the PV curves of the objective grid and its partial grids and the VQ curves of 500 k V buses in the different periods of ultra-high voltage access were calculated by using the above method.The results show that the static voltage stability margin of Hebei Southern Power Grid is high both in the typical operation modes of 2017 and 2020.With the development of UHV and 500 k V grid,the static voltage stabi lity level of the objective grid in 2020 is better than in 2017.In addition,the results of short circuit ratio and effective short circuit ratio indicate that the Cangzhou converter bus is static voltage stable,and the objective grid is a strong receving system in 2020.Voltage collapse usually begins with one or more weak buses in the power system.In order to consider the influence of both active and reactive power in the identification of weak bus,a new integrated voltage stability index was proposed by the integration of active margin index and voltage-reactive power sensitivity index,which are commonly used in engineering practice,based on ideal point method,and its weight allocation was demonstrated in detail.Weak 500 k V buses of Hebei Southern Power Grid in the different UHV access stages was identified by using the new integrated index,which not only improves the results of static voltage stability analysis that are useful for subsequent improvement and reactive power configuration,but also verifies the practicability and validity of the new index.UHV access Hebei Southern Power Grid is a nonlinear system with many dynamic components,and voltage collapse always occurs in the system's dynamic process under large disturbance.The transient voltage stability of the grid both in 2017 and in 2020 is analyzed based on time domain simulation in this paper,including AC fault,DC fault and complex fault of AC/DC.The results show that Hebei Southern Power Grid can meet N-1 principle in the different UHV access stages,and maintain voltage stability after the specified serious fault conditions.With the development of UHV and 500 k V grid,the transient voltage stability level of the objective grid in 2020 is better than in 2017.Additionally,it is worth to be further studied that the corresponding control strategy in order to eliminate the fluctuation of bus voltage and line power flow in the stable system after faults.