Towards Asymmetrical Modeling of Voltage Stability in the Presence of GICs

Geomagnetically induced currents (GICs) disturb power systems. Conventional modeling with waveform-symmetrical reactive power (Q) does not characterize the half-wave saturation of transformer cores, their non-linear inductance, and the harmonics generated. The relative directions of flow of GIC and power are not the same in all transformers, with the result that the fundamental half-wave effect is not the same in all. In this study, we used a real-time OPAL-RT-MATLAB/Simulink platform to model the response of 4- and 6-bus power systems with dc representing different geoelectric field vectors. The symmetrical shunt reactor approach to GICs and voltage stability under-estimates the effects of transformer dynamic inductance and distortion compared with a simulation of asymmetric distortion. Compensation based on the general power theory mitigates the GIC effect on transformers and improves power system voltage stability during geomagnetic disturbances (GMDs).