大型汽轮发电机负序运行时磁力热特征研究

发布时间：2018-06-11 23:19

本文选题：汽轮发电机 + 负序运行　；参考：《哈尔滨工业大学》2017年博士论文

【摘要】：大型汽轮发电机在我国电力系统以及国民经济发展中占据重要位置,其稳定运行能力直接关系到电网的安全与稳定。负载不对称是大型汽轮发电机常见的运行状态,由此引发的负序分量会在汽轮发电机中引起磁场畸变、转子温升、转矩脉动,危害发电机运行安全与寿命,影响机组系统的运行安全。已有文献对负序运行能力进行了限定,而对负序运行状态诱发的电机内电流、磁场、电磁力、电磁转矩以及温度等特征参量的变化机理未做深入研究。论文围绕负序产生机理、负序运行状态下的磁场分布、电磁转矩、负序运行状态下的转子温度场等特征规律进行重点研究。根据大型汽轮发电机运行特征和系统要求,在研究负序运行基础理论和特征量计算方法的基础上,阐明了负序电流对大型汽轮发电机产生危害的机理,结合汽轮发电机不对称运行的拓扑结构,推导出了定子单相接地短路和两相短路暂态负序电流的表达式。在此基础上,应用电机稳态运行分析理论和磁动势矢量轨迹表达式,给出了多种负序分量条件下汽轮发电机合成磁动势轨迹图,揭示了负序分量对汽轮发电机磁动势轨迹的影响规律。以某大型核电汽轮发电机为例,结合工程运行要求,确定出了其稳态负序和暂态负序运行能力。在分析大型汽轮发电机负序运行过程和磁动势特性的基础上,结合麦克斯韦电磁场矢量磁位微分方程,建立了汽轮发电机二维电磁场场-路-运动耦合数学模型。以某大型汽轮发电机结构数据为基础,通过对电机结构的合理简化,建立了汽轮发电机负序运行的物理模型,并通过真机空载与短路实验,验证了模型的合理与有效性。在此基础上,分别对汽轮发电机在额定工况和多种负序分量含量条件下的磁场进行了计算,对比分析了同一负序分量条件下,电机运行在不同时刻时的磁密分布特征,以及不同负序分量条件下,同一时刻的磁密分布特征,同时对空载、额定和含极限负序分量条件下气隙磁场特性进行了分析,确定出了转子大齿表面磁场时-空变化规律和负序分量对磁场分布的影响规律。结合同步电机磁动势行波表达式和虚位移法,推导出了含负序分量运行条件下汽轮发电机的电磁转矩表达式,明确了含负序分量运行条件下二倍频电磁转矩产生的机理。通过对额定工况和不同负序分量影响下电磁转矩的数值计算及转矩频谱特性的分析,揭示出了正序分量相同,负序分量不同状态下,以及负序分量相同,而正序分量不同状态下电磁转矩的变频规律。同时对负序运行状态下励磁绕组以及转子槽两侧的受力分布进行了计算,分析了额定工况和多种负序分量下励磁绕组和转子槽壁的受力分布特征,揭示了负序分量对其分布的影响规律。针对汽轮发电机转子大齿有无阻尼,转子槽楔采用磁性或两种非磁性材料的情况,计算了汽轮发电机电枢电流存在负序分量时,汽轮发电机的电磁场分布、气隙磁密波形和各次谐波。选取汽轮发电机转子轴向中心位置的二维截面为其温度场求解区域,建立了汽轮发电机二维稳态温度场分析数学模型,基于电磁场分析结果,对比研究了汽轮发电机转子采用不同槽楔,电枢电流存在负序分量时,汽轮发电机转子温度场的特征规律。本论文的研究,可为大型汽轮发电机的结构设计、运行性能分析以及负序问题的研究奠定基础。
[Abstract]:Large turbogenerator occupies an important position in China's power system and the development of national economy. Its stable operation ability is directly related to the safety and stability of the power grid. The load asymmetry is the common running state of large turbogenerator. The negative sequence component will cause magnetic field distortion, rotor temperature rise and torque in the turbo generator. The fluctuation, which endangering the safety and life of the generator, affects the operation safety of the unit system. The existing literature has limited the negative sequence operation ability, and the mechanism of the change of the characteristic parameters such as the current, magnetic field, electromagnetic force, electromagnetic torque and temperature induced by negative sequence running state has not been studied deeply. The characteristics of magnetic field distribution, electromagnetic torque and rotor temperature field under negative sequence operating state are studied in negative sequence. Based on the operation characteristics and system requirements of large turbogenerator, the negative sequence current is introduced to large turbogenerator on the basis of the study of the basic theory of the negative sequence operation and the calculation method of the characteristic quantity. The mechanism of the harmfulness is combined with the topology of the unsymmetrical operation of the turbogenerator. The expression of the stator single-phase grounding short circuit and the transient negative sequence current of the two phase short circuit are derived. On this basis, the synthetic magnetodynamics of the turbogenerator are given under the conditions of the steady operation of the motor and the expression of the magnetic potential vector trajectory. The influence of the negative sequence component on the magnetodynamic potential trajectory of a turbogenerator is revealed. Taking a large nuclear power turbo generator as an example, the steady negative sequence and transient negative sequence operation capacity of a large turbogenerator are determined. On the basis of the analysis of the characteristics of the negative sequence operation and the magnetomotive force of the large turbogenerator, Max is combined with the performance of the large turbogenerator. On the basis of the structure data of a large turbogenerator, the physical model of the negative sequence operation of the turbogenerator is established on the basis of the structure data of a large turbogenerator, and the model is verified by the real aircraft no-load and short circuit experiment. On the basis of this, the magnetic field of the turbogenerator under the condition of rated working condition and a variety of negative sequence components is calculated, and the magnetic density distribution characteristics of the motor at different times under the condition of the same negative sequence component and the magnetic density distribution at the same time under the condition of different negative sequence components are compared and analyzed. At the same time, the air gap magnetic field characteristics under the condition of no load, rated and limit negative sequence components are analyzed. The law of time to air change and the influence of negative sequence component on the distribution of magnetic field are determined. The vapour containing negative sequence component is derived in combination with the expression of magnetic potential wave of synchronous motor and the method of virtual displacement. The electromagnetic torque expression of the wheel generator, the mechanism of the generation of two frequency doubling electromagnetic torque under the operating condition of negative sequence component is clarified. Through the numerical calculation of the electromagnetic torque and the analysis of the torque spectrum characteristics under the influence of the rated working condition and the different negative sequence components, the positive sequence components are identical, the negative sequence components are in different states and the negative sequence components are found. At the same time, the frequency conversion law of electromagnetic torque under different positive sequence components is calculated. At the same time, the force distribution of excitation windings and rotor slots on both sides of the rotor slot under negative sequence operation state is calculated. The characteristics of the force distribution of the excitation winding and the rotor slot wall under the rated working condition and a variety of negative sequence components are analyzed, and the influence of the negative sequence component on its distribution is revealed. According to the condition of magnetic or two non magnetic materials, the electromagnetic distribution of the turbo generator, the air gap magnetic density waveform and the harmonics are calculated for the rotor slot wedge using magnetic or two non magnetic materials. The two-dimensional cross section of the axial center position of the turbogenerator rotor is selected. The mathematical model of the two-dimensional steady temperature field analysis of the turbogenerator is established. Based on the results of the electromagnetic field analysis, the characteristics of the rotor temperature field of the turbo generator rotor are compared with the different slot wedges and the armature current has negative sequence. This paper can be used as a large turbogenerator. It lays a foundation for structural design, performance analysis and negative sequence research.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM311

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