Research On The Magnetic Properties Of Transformer Core Under Harmonic Excitation

With the wide application of AC/DC hybrid transmission,the introduction of the DC transmission system makes the voltage and current in the power grids distortion,resulting in harmonic pollution.Transformer is the important electric equipment in power system,and the existence of harmonics will cause many adverse effects on the transformer,such as increase losses of transformers,local overheating,generate nosie pollution,etc.,is unfavorable to the safe operation of power grid.Transformer core as a core part of the transfmer decides the performances of power transformers.So the magnetic measurements and loss characteristics research of transformer core under harmonic excitation play an important role in electromagnetic design and structural optimization of transformer?The main works are as follows:1.this article use product-level transformer core model,a measurement platform can be used to generate harmonic excitation was set up.Different harmonic excitations were applied to the core model.The effects of the change of harmonic phase,frequency and order on iron hysteresis loop and iron loss were studied.It would provide experimental data of identification of hysteresis model and iron loss study in the following text.2.based on the Jiles-Atherton hysteresis model,the expression of it were be derived and the effects of hysteresis parameters on hysteresis loop were studied.The genetic algorithm and artificial fish swarm algorithm were adopted to solve the hysteresis parameters and compared with the experimental data,the feasibility of gorithms were verified.3.based on the Preisach hysteresis model,according to the symmetry of hysteresis loops,an identification method of Preisach distribution function was proposed.It is proved that the method is applicable to the hysteresis loop of the iron core under sinusoidal and harmonic excitation by the comparison between calculated values and experimental data.4.simplified modeling of iron core model by use MagNet,a electric magnetic simulation software,compared with solid modeling simulation.The magnetic field distribution and loss calculation method of transformer iron core under sinusoidal and harmonic magnetic field were studied.