Research On Sereval Issuses Of Generator/Motor Starting With SFC During Forced Commutation

The research on the starting process of generator/motor with static frequencyconverter (SFC) is a synthesis problem, which involves power electronic controland electro machine dynamic analysis theory. As the high capacity and complexcomposition of SFC starting system, and on account of the coordinate influenceof generator/motor and power grid, meanwhile the forced commutaion is aimportant link of successful starting process, the investigation of the relatedproblems during the forced commutation starting process are with theoreticalsignificance and practical value in engineering to improve the stability andlocalization of starting system equipment.In this dissertation, some documents about the starting process ofgenerator/motor, control and operation of SFC at home and abroad were analyzed,the development state of the related issues about the generator/motor startingwere also discussed, the problems existing in the forced commutation startingprocess were analyzed and the shortcomings of the published paper research werepoint out, then the main study content of this destination were confirmed.On the basis of the analysis of the structure characteristics of generator/motorSFC starting system, the functions of starting system components wereexpounded and the detection method of static rotor position and rotatedcharacteristic of magnetic motive force during starting process were analyzed,and then the production mechanism of electromagnetic torque forgenerator/motor during forced commutation starting process with SFC wereexplained in detail.Based on the investigation and analysis of the initial rotor position determiningmethod and converter control program for the normal stopping location for generator/motor starting with SFC, the starting control problem of initialconverter program for the special stopping position of generator/motor wasproposed. And through the analysis of stator winding induction voltages of initialstarting moment, the specific special stop position was pointed out. After that, theelectromagnetic torque with different converter control program for the specificstopping location was calculated with finite element method, and then theconverter control program for the specific location was proposed, the existence ofthe specific position and the correctness of the converter control program wereverified with experiment. Finally, the starting control theory of generator/motorstarting with SFC was improved.The current commutation characteristic during the forced commutation ofgenerator/motor starting with SFC was analyzed, and the accurate calculationmodel in the armature current commutation process for the forced commutationstage was established, furthermore, the current harmonic characteristics werecalculated based on the simplified model and accurate model respectively, and theshortcoming of the simplified model was pointed out. In this foundation, theexpressions of stator magnetic motive force and electromagnetic force werededuced based on the current accurate calculation model, and the harmonic ofstator magnetic motive force and electromagnetic torque in the process of forcedcommutation was analyzed. In addition, the forced commutation starting processwith SFC of a generator/motor prototype was calculated with FEM, the results ofwhich verified the validity of the current accurate calculation model and theanalysis of harmonic characteristics. So the accurate calculations of harmonic forfilter design of static frequency converter system were solved. According to thecharacteristic of SFC starting system for generator/motor, the approach wasproposed to suppress the harmonics in generator/motor based on the match ofstator and rotor magnetic motive force, and then the variation of generator/motormagnetic field distortion and match coefficient of stator and rotor MMF wasfound through the calculation of matching coefficient when the rotor located ondifferent position during forced commutation, which provides a new idea for thechoice of SFC starting system for generator/motor.Fault models of SFC starting system for generator/motor were summarized andanalyzed, and the fault-tolerant operation feasibility was proposed by means of the investigation of the magnetic motive force with an open bridge of SFCinverter bridge. And then the time-step FEM model of generator/motor startingwith SFC was established and verified with experimental tested results, after that,the starting process of generator/motor starting with an open bridge of SFCinverter bridge was calculated with time-step FEM, and the variation of speedand electromagnetic torque according to the open bridge fault at different timeswere obtained, the fault-tolerant with an open arm of SFC inverter bridge wasverified. Meanwhile, the improved fault-tolerant converter control program wasproposed on the basis of the rotor position at different times, and the validity ofthe improved control program was verified with the FEM calculation results.Besides, the diagnostic method of SFC with an open arm fault of inverter bridgewas proposed in accordance with the characteristic analysis of stator windinginduced voltages after inverter bridge fault, and a new detection mean wasprovided for the thyristor condition monitoring of SFC.Investigation contents of this thesis are able to provide some theory referencesfor the research and development of China’s large capacity SFC starting system,and there is important practical significance to the generator/motor safety, stable,efficient operation.