【作者】 许国瑞；

【导师】 罗应立； 刘晓芳； 王红宇；

【作者基本信息】 华北电力大学 ， 电机与电器， 2014， 博士

【摘要】 同步发电机在扰动后的动态运行能力对于系统安全稳定运行具有重要意义。本文建立了用于研究扰动条件下发电机运行能力的时步有限元模型,研究了汽轮发电机转子复杂阻尼结构及其材料特性对系统稳定性的影响,并与电力系统仿真分析所用的发电机三种实用模型的计算结果进行了对比研究。在此基础上,以时步有限元结果作为标准响应,辨识了发电机大扰动过程中的电机参数。主要成果如下：1.建立了用于分析汽轮发电机转子三部分阻尼结构和阻尼材料特性对其动态运行能力影响的时步有限元模型,对该模型的时空离散策略进行了优化和改进,使其能够更加准确的计及多因素非线性条件下转子阻尼结构中的涡流集肤效应,并通过模型机试验验证了该模型的准确性。2.以一台300MW汽轮发电机为例,通过详细的时步有限元计算分析,揭示了汽轮发电机转子大齿导条、转子铁心和转子导电槽楔等阻尼结构与发电机第一摆稳定性之间的关系,发现转子阻尼结构对第一摆稳定极限的影响主要取决于其等效电阻；进一步对转子槽楔采用不同材料时发电机的第一摆稳定性进行研究,揭示了第一摆稳定极限随转子槽楔电导率的变化规律。3.揭示了实用模型两种假设条件的物理本质,假设A模型计及了励磁绕组和阻尼绕组的互漏磁链,忽略了阻尼绕组自漏磁链；假设B模型反之；在假设B模型的基础上进一步对阻尼相关项进行简化得到了假设B-1模型。在此基础上,对比分析了时步有限元模型与三种实用模型所计算的大扰动和小扰动结果,得出不同模型仿真结果之问的差异。4.将解析法和数值仿真相结合研究了实用模型中定子绕组电磁暂态对发电机机电暂态过程的影响,发现忽略定子绕组暂态后,发电机三相突然短路过程中的交变电磁转矩分量和定子非周期电流产生的单向电磁转矩分量均被忽略,而后者属于制动性质的转矩,被忽略后会影响功角第一摆稳定性的仿真精度。5.以时步有限元结果作为目标曲线,采用最小二乘法辨识了发电机大扰动过程中的电机参数,揭示了这些参数随发电机功角的变化规律,得出辨识参数计算结果的精度明显高于厂家参数。同时,对转子导电槽楔采用不同材料时的发电机参数进行辨识,得出转子槽楔电导率对发电机各参数的影响。研究结果为实用模型的进一步改进提供了理论支撑。更多还原

【Abstract】 The dynamic operation capacity of synchronous generator after disturbance of power system is very important to guarantee the safety and stable operation of power system. This dissertation has established Time-step Finite Element Model (T-S FEM) to study the operation capacity of synchronous generator under system disturbance, and studied the influence of rotor damping structure and damping material characteristic of turbine generator on power system stability. The results calculated by T-S FEM are compared with the practical models of synchronous generator used in power system simulation. Take the results of T-S FEM as target curves, the parameters of practical model in large disturbance process is identified. The main works are as below.1. The Time Step Finite Element Model used to analysis the influence of three components damping structure of turbine generator and damping material characteristic on dynamic characteristic of power system is built. Considering the complex rotor damping structure of turbine generator, we make crucial improvements in space-time discrete strategy to consider the eddy current skin effect of rotor damping structure affected by multi-factor nolinear. This model is tested by the experiment of model machine.2. Take a300MW turbine generator as an example; we reveal the relationship between rotor damping bar, rotor conductive slot wedge, rotor iron core of turbine generator and the First Swing Stability through the computational analysis of T-S FEM. And we also find that the influence of rotor damping structure on First Swing Stability is depended on its equivalent resistance. Further, we study the First Swing Stability affected by rotor slot wedge of different materials and reveal the change law of first swing stability limt along with the conductivity of rotor slot wedge.3. The physical essence of two practical models is reavled in theory. The assumed A model takes account of the mutual leakage flux linkage between field winding and damping winding, neglects the self-leakage flux linkage of damping winding; it is opposite to the assumed B model; while assumed B-1model is obtained by neglecting the something about damping based on assumed B model. The simulation results of small disturbance and large disturbance by three practical models is compared with the T-S FEM, and the results difference of different models is obtained.4. The influence of stator winding transient (p(p) on electromechanical transient is studied by analytical expression and numerical simulation. It is found that the fundamental frequency oscillatory component of electrical torque and unidirectional component of electrical torque due to stator aperiodic current during three phase short circuit of generator is neglected, when the stator winding transient is neglected. The unidirectional component of torque has a braking effect. Its effect is to reduce the rotor acceleration following the disturbance and improve the first swing stability.5. Take the large disturbance results of T-S FEM as target curves, the parameters of synchronous generator are identified through the least square method. We obtain the change law of these parameters along with power angle of generator and find that the precision of identification parameter is higher than factory parameters. Meanwhile, the parameters are identified under different rotor slot wedge materials and find that the influence of rotor slot wedge conductivity on the paremeters of generator. The study results provide theoretical support for the further improvement of practical model.更多还原