Review of harmonic losses in HVDC converter transformer: Its causes and mitigation techniques

Due to the disturbances created in the various layers of the Earth's atmosphere, the geomagnetic field interacts with the electric field of Earth. This induces voltages in the pipes, telecommunication circuits, transmission lines, etc. leading to the creation of geomagnetically induced currents (GIC). The GIC when flows through the neutrals of transformer, it results into the saturation of transformer core, generation of harmonics and various other adverse effects. DC bias is an important consequence of the invasion of GIC into the converter transformer neutrals. This paper describes about the effects of GIC on the converter transformer and also the measures to inhibit GIC is revealed. Further various methods to reduce harmonics due to GIC are studied.