Transformerless Converter-based GMD Protection for Utility Transformers

Geomagnetic Disturbances (GMDs) have long been the cause of various power system failures thus affecting the power system stability and security. Their major effect on power systems is the injection of Geomagnetically Induced Currents (GICs) among the long length transmission lines. This phenomenon, particularly, leads to transformers saturation and consequent damages. This paper proposes a novel power electronic-based GICs mitigation approach for utility transformers that involves a transformerless series active filter integrated between the neutral point and earth ground serving multiple purposes. The first objective is to surpass the effect of GICs, while the second goal is voltage regulation and the third is to provide harmonic isolation. The system circuitry, operation and control are implemented and further verified in a Controller Hardware-in-the-Loop (C-HIL) test setup with Typhoon HIL 402 simulator. Results indicate that our approach is a promising alternative to traditional neutral capacitor blocking strategies.