Research Of DC-biasing Characteristics Of The Transformer Core

Magnetizing characteristics of power transformer and normal operation of powergrids are affected by the quasi-direct current and the direct current caused from the solarmagnetic disturbance and the HVDC system respectively. Analysis of DC-biasingmagnetizing characteristics is of great engineering significance on the safe operation ofthe power system, the design and manufacture of the power transformer.A laminated core and a single-phase three-limb transformer are applied to carry outthe DC biasing experiment. The harmonic balance method is combined with theelectromagnetic coupling circuit model of transformers in different structures, accordingto the steady-state characteristics of electric and magnetic circuit under DC biascondition. The harmonic balance equation has been set up to compute the harmonicvectors of exciting current and magnetic flux by updating the nonlinear reluctance infrequency domain.At the end of this thesis, The fixed-point method is introduced into theelectromagnetic coupling circuit model of the laminated core, combining with theharmonic balance method. A fixed-point harmonic balance method is presented,considering the electromagnetic coupling circuit model. Hysteresis effects under normaland DC bias condition are simulated and the calculated magnetizing currents agree wellwith the measured one by using the fixed-point harmonic balance method.