Research On Operation Of Turbine Generator Considering Saturation And Magnetic Field Distortion

The thesis studies features of magnetic field distribution of turbine generator as affected by magnetic saturation and magnetic field distortion and their influences on operation. The operating states of research include normal states as well as critical states with bigest power angles. These can provide theoretical basis and technical support to further create accurate models of generators used in power system simulation. The main achievements of the thesis are shown below:1) By comparative study of researching different voltage equations in the field-circuit coupled analysis, applying limitations of classic equation giving in some references is found. The new form of voltage equation is got to reflect characters of magnetic field distribution and influences of harmonic components.2) Through comparion analyse of magnetic field distribution, magnetic flux density waveform, inductive electric potential and so on under different saturation degrees and power angles, it is found that the combined action of magnetic saturation and magnetic field distortion not only causes that the load nonlinear characteristics deviate obviously from no-load characteristic, but also leads to the prominent changes in symmetry of magnetic flux density space waveform and its harmonics content. And these changes also result in the deviation of air fundamental magnetic density axial line and more harmonic components of the time waveforms of potential and magnetic flux density on stator teeth.3) On the basis of former study of nonlinear characteristics of 300MW turbine generator, four turbine generators of 135MW,200MW,300MW and 600MW are taken as examples to study systematically their common traits of load nonlinear characteristics and explore the general rules. The study reveals the prominent distinction between load nonlinear characteristics and respective no-load characteristic under different operating conditions. The distinction is due to magnetic saturation and magnetic field distortion widely existed in large turbine generators under load conditions.4) By analyzing deeply results by FEM, the new curve series of turbine generator are got among the operating quantities of air-gap potential, resultant MMF, power angle, power factor and so on by magnetic saturation and magnetic field distortion. Then the new method is presented to calculating load field currents, in which no-load characteristic is substituted by the new series. And the method reserves the precision of FEM and is easy to use in engineering.5) The calculating methods of electromagnetic torque and parameters are compared and studied to choose applicable method. Through analyzing a large number calculation, the influences are small on power angle curve and bigger on parameters by magnetic saturation and magnetic field distortion. And synchronous reactances are decreased notably with the increase of power angles in fixed air-gap potential, namely the unchanged saturation degree of main magnetic path.