Sensitivity analysis of power system small signal stability to geomagnetic disturbances

Abstract

Geomagnetically induced currents driven by geomagnetic disturbances can cause half-cycle saturation of transformers and consequently affect the power grid with reactive losses. The impact of geomagnetic disturbances focuses on voltage stability, and the research object is the conventional system without considering wind power. In this paper, we study the impact of geomagnetic disturbances on the small signal stability of doubly-fed induction generators integrated systems. After the reactive power loss caused by geomagnetic disturbances and wind power output are equivalent to grounding admittances, the influence of geomagnetic disturbances on small signal stability can be transformed into its impact on the equivalent electrical distance between synchronous generators by shrinking the admittance matrix. Then, the electromagnetic power of synchronous generators is affected, and the impact of wind farm ratio and geomagnetic disturbances is incorporated into the system state equation. The results show that the oscillation frequency and damping ratio increase first and then decrease with the increase of wind power ratio when geomagnetic disturbances occur, but they are generally smaller than those without geomagnetic disturbances. The sensitivity of inter-area oscillation mode to induced geoelectric fields is higher than that of intra-area oscillation modes, and the sensitivity to reactive power losses caused by geomagnetic disturbances in substations is different, which provides a reference for further research on optimizing blocking devices placement to mitigate the impact of geomagnetic disturbances on small signal stability.