Research On GIC Harmonic Characteristics Of UHV AC Power Grid

Geomagnetic storms will cause the generation of geomagnetically induced current(GIC).GIC flows from the neutral point of the transformer,causing the transformer to become a source of harmonics.In the UHV AC power grid,a large number of harmonics will be injected into the power grid,which seriously affects the power in the power grid system.Quality and stable operation,so far,few people have studied the distribution of power grid harmonics caused by GIC.For the harmonics of the power grid in my country,the GIC current is mainly distributed in the UHV AC power grid.Therefore,the study of the harmonic characteristics caused by GIC is of great significance for understanding the harmonic characteristics of the UHV AC power grid under the action of GIC.This paper firstly analyzes the DC bias harmonic response characteristics of the single-phase four-phase column UHV autotransformer developed in my country based on GIC.Based on the action of GIC,the interaction between the transformer main body and the main leakage flux is considered.The harmonic calculation model of the UHV autotransformer,according to the relevant design parameters of the existing UHV transformer,the UHV transformer under the action of GIC is modeled in EMTDC,and the voltage and current characteristic curves of the simulation model are compared with the transformer equipment test.The curves in the report are compared to study the harmonic current distribution of each winding of the UHV transformer under the action of GIC.Using the above UHV transformer model,the electromagnetic transient simulation software PSCAD/EMTDC is used to establish a simple power grid transmission model based on a transformer,and its simulation characteristics are analyzed.Then the simulation model of 1000 k V UHV AC transmission system based on the full-node model of Sanhua Power Grid is carried out for simulation research.According to the harmonic analysis method,the obtained simulation results are analyzed.The harmonic characteristics of 1000 k V UHV AC transmission lines under the action of GIC are studied and analyzed.The simulation results show that when GIC is not taken into account,the harmonic content of the 1000 k V line is dominated by the 5th harmonic,and the content of the other voltage harmonics is relatively small,and the distortion rate of the 5th harmonic is 0.86%.When GIC is considered,when the GIC current acts on a transformer,the distortion rate of each harmonic decreases with the increase of the length of the line,and each harmonic in the line increases to a certain extent,and the harmonic distortion rate increases.The most obvious ones are the 3rd and 5th harmonics.When the GIC in the system continues to increase,the distortion rates of the 3rd harmonic and the 5th harmonic also gradually increase.When the GIC increases to 100 A,the distortion rates of the 3rd harmonic and the 5th harmonic are 1.73 %,2.67%.Therefore,the harmonics of the power grid increase under the action of GIC,which is more harmful to the power grid.