Impacts of Uncertain Geomagnetic Disturbances on Transient Power Angle Stability of DFIG Integrated Power System

When geomagnetic disturbances (GMDs) occur, the reactive power loss (GIC-Q) caused by geomagnetically induced currents (GICs) flowing through transformers can lead to system instability. Previous studies have been focused on the impacts of GMD on the static stability of conventional systems, while transient stability of hybrid systems left unexplored. In this article a hybrid system based on wind and conventional energy sources are proposed as a research object. The wind farm output power and GIC-Q are equivalent to the grounding impedance. Considering the uncertainty of GMD, based on establishing the random fuzzy model of induced geomagnetic fields, the expected value of critical clearing angle and acceleration/deceleration area is calculated by using credibility theory. Then the influence of GMD on the transient stability under the different proportions of wind farm output power is analyzed quantitatively by using transient stability margin. Taking the Mengdong power grid under four operation modes as an example, the results show that no matter which operation mode, the transient stability of the system is reduced when GMDs occur. Under heavy loading conditions in summer and when the proportion of wind farm output power reaches 50%, the transient stability of the system is the lowest. The research results provide a basis for disaster prevention and control of GMDs.