The Study On Electromagnetic Simulation Model And Algorithm Of Power Transformers

Recently, as national economy develops rapidly, power system is becoming more and more bulkiness and complexity. The safe and stable operation of power system is important guarantee for economical development. Power transformer is the significant equipment of transferring and transf orming power in the power system, as a result, it is necessary to research the electromagnetic transient course in the power transformer. At the same tim e power sys tem num eral simulation is the v ital m eans in the electromagnetic transient course. With the increasing demand of system operation, the calculation speed and sim ulation accuracy of the power system simulation an d simulation accuracy are also put forward higher requirements.First, the b asic prin ciple of ana lysis electromagnetic transient sim ulation and primary method of numeral simulation in power system was studied deeply. Based on the analysis and summary of existing m odel of power transform er, integrating the transformer model of controlled source prin ciple and damping trapezoidal integration method, electromagnetic transient simulation model in power transformer was set up, which including nonlinear exciting branch. The saturated nonlinear characteristic of transformer core was research ed based on this model. Ther e would be m agnetizing inrush currents, when transform er is no- load switching or rem oving fault external. The sim ulation f or magnetizing inrush cu rrents shou ld ref lect th e satu rated characteristic of transformer perfectly. The trad itional piecewise linear approach is simpler and costs little amount of calculation dealing with nonlinear matter of exciting branch. But a"overshoot"distortion probl em would happ en when it cam e to the simulating calculate. Generally, it w ould suppress the overshoot problem effectively that reduce the sim ulation step-size, but it incr eased simulating time badly, whic h made the a dvantage of piecewise linear app roach lost. Based on the physical characteristics of the transfor mer, predictor-corrector algorithm was proposed, which was the improvem ent of piecewis e linear app roach. First, back to saturation of the magnetizing current was predicted, when the saturation point in the forecast crossing, the correction for mula took the p lace of orig inal form ula calcu lating m agnetizing current, then the simultaneous node voltage equations were gotten which could m ake the ele ctromagnetic simulation of the whole network. This m ethod solved the overshoot problem and maintained the reasonable but greater integration step-size. In the later stage of this paper, based on th e basic m odel, transformer fault model of inter-turn short was established by analysis of the principle of inner fault in transformer. Differing from building an exte rnal circuit, this m odel could sim ulate internal faults directly, which was easy to use and would help to further analysis.The established transform er m odels we re val idated by t he el ectromagnetic transient simulation program which was programmed by the author. The analysis and contrast of exam ples validated th e m odels and sim ulation process correct and effective. The sim ulation m odels and al gorithm were worth for electrom agnetic transient's theoretical analysis and simulation research.