Real-Time Monitoring Method of Power Grid Voltage Stability During Geomagnetic Storms

During geomagnetic storms, geomagnetically induced currents are induced in power grids that flow through the grounded transformers' neutral points and increase the transformers' reactive powers. The resulting excessive and group reactive power disturbance results in voltage fluctuations in the power grid and even cause voltage collapse. Therefore, the stability of power grid voltage needs to be monitored in real-time during geomagnetic storms. This study proposes a real-time monitoring and evaluation method for power grid voltage stability based on the Thevenin equivalent technique and synchronous phasor measurement units (PMUs). The proposed method develops an equivalent circuit model to reflect the impact of transformer excitation branch changes on system impedance during geomagnetic storms. Thevenin equivalent parameters are obtained using electrical quantities determined by synchronous PMUs to quantitatively evaluate the voltage stability margin of each node during geomagnetic storms and monitor the voltage stability of the power grid in real-time. The proposed method can provide a reference for ensuring the voltage stability of grids during geomagnetic storms and prevent voltage collapse; further, case studies conducted on IEEE 118-GMD verify the validity of the method.