Research On Mechanism Of Turbo-Generator Nonlinear Characteristics And Its Relation To Operating Conditions

The complex nonlinear characteristics of turbo-generator operating under variousconditions are studied in this thesis. The thesis proposes that nonlinear characteristics curvesof large generators include four typies. Three inner factors inducing the difference ofnonlinear characteristics curves are analyzed quantitatively including the main magnetic fluxcausedsaturation,excitedcurrent causedsaturationandmagneticfielddistortionnonlinearity.The relationship between these factors and operating conditions are discovered. Finally, thenonlinear model machine is further studied and designed. The work and attribute of the thesisisshownbelow:1)Load characteristics of turbo-generator under different operating conditions arestudied. The analysis shows that these curves include four types. Load characteristics of thefour cases are compared and it finds that most of them have great discrepancies from no-loadcurves and there are also discrepancies among these curves. In some cases, the discrepancymayreachto100%.2)Thesolutionandtheexpressionofmagneticdensityandmagneticpotentialaregivenin this thesis. Theyare used to quantitativelydescribe the inner nonlinear degree. Three innerfactors causing the difference of outer load characteristics are introduced. It shows that thethree inner nonlinear factors are the essential reasons resulting in the complex loadcharacteristics.3)Through extensive study it discovers that: The main flux saturation is influenced bythe terminal voltage and the power angle; the excited flux leakage caused iron saturation isnot only affected by the excited current but also affected by the power angle; while themagnetic field distortion is influenced bythe power angle, the excited currents and the q-axiscurrent.Undersomeconditions,theeffectiveair-gapmaybethreetimesofmachineair-gap.4)Through the numerical calculation and test research on a 7.5kW model machine, itshows that this model machine could not model the characteristics of the 300MW generatorexactly due to the structure difference. Through the analysis on the typical operatingconditions of the load and no-load characteristics of the 7.5kW and 300MW, the thesisdiscovers that a proper structure is the key problem of a good model machine. According tothe above conclusions, a 30kW model machine with novel structure is designed. The resultsshow that load characteristics of 30kW machine are ideal and can model the 300MWgeneratorwell.5)Theleastsquaremethodisusedtoestimatethelinearparametersof300MWgenerator.The saturated parameters xa dand x aqare calculated with the outside conditions changing.The analysis shows that the inner nonlinear factors are the essential cause making theparameterschanging.