【作者】 朱二夯；

【导师】 梁艳萍；

【作者基本信息】 哈尔滨理工大学 ， 电机与电器， 2023， 博士

【摘要】 大型同步调相机具备强大的动态无功补偿能力和短时过载能力,已成为特高压直流输电系统中重要的无功补偿装置。在特高压直流输电系统电压跌落故障过程中,大型同步调相机向电网瞬时发出大量的无功,强大的冲击电流导致调相机端部结构件中感应出较大的涡流损耗并引起发热,严重威胁调相机本体及电力系统的安全运行。因此针对以短时强暂态运行为特点的大型调相机,分析调相机端部结构件磁场、损耗与温升是大容量调相机设计与运行的关键技术之一。本文以一台300MVar大型同步调相机为研究对象,围绕特高压直流输电系统故障过程中大型同步调相机暂态特性、端部区域磁场、端部结构件涡流损耗及温升问题进行研究。建立大型同步调相机机-网耦合暂态模型,分析特高压直流输电系统送端交流电压短时和持续故障过程中调相机暂态特性,研究大型同步调相机对特高压直流输电系统送端交流电压故障程度下的调节能力,揭示大型同步调相机在输电系统不同故障下的暂态无功特性及其影响因素。通过与实测结果对比,验证大型同步调相机机-网耦合暂态分析模型的准确性。提出求解大型同步调相机端部区域磁场和压圈涡流损耗的三维解析计算方法,建立空间位置的虚拟等效电流,计及铁心背部和转轴对端部区域磁场的影响。结合有限元法实现大型同步调相机端部区域磁场和压圈涡流损耗的计算,分析压圈材料特性和结构参数对涡流损耗的影响,有效解决工程研发初期阶段求解大型电机端部区域磁场和结构件涡流损耗时网格剖分困难、计算时间长和计算机配置需求高的难题。通过与三维有限元法计算结果和计算时间进行对比,验证所提出的方法的准确性和高效性。提出能够有效减小端部结构件涡流损耗的新型屏蔽与压指拓扑结构。分别建立传统结构和新型结构下的三维非线性瞬态电磁场计算模型,计算大型同步调相机稳态、暂态运行工况下端部区域磁场和端部结构件涡流损耗的分布规律,对比端部结构件磁通密度和涡流电密最大值区域,验证所提拓扑结构的有效性。建立大型同步调相机端部区域三维流热耦合计算模型,结合调相机端部结构件涡流损耗的分布规律,构建端部结构件子区域网格,以子区域的涡流损耗作为热源,将给定的风扇入口流速和出口压力值作为其边界条件,计算大型同步调相机额定运行工况下的流热耦合场,分析调相机端部区域的流体速度和温度分布规律,揭示端部结构件损耗、冷却条件与温升分布的关系,探究所提出的端部屏蔽拓扑结构与压指拓扑结构对端部流体及端部结构件温升的影响,并与实测结果进行验证。更多还原

【Abstract】 Large synchronous condenser has strong dynamic reactive power compensation capability and short-time overload capability,and has become an important reactive power compensation device in Ultra-high voltage direct current(UHVDC)transmission system.In the process of voltage drop fault in the UHVDC transmission system,large synchronous condenser sends out a large amount of reactive power to the power grid instantaneously.The strong impact current leads to large eddy current loss induced in the end structure of the synchronous condenser and causes heating,which seriously threatens the safe operation of the synchronous condenser and power system.Therefore,the analysis of the magnetic field,loss and temperature rise of the end structure is one of the key technologies for the design and operation of large synchronous condenser,which is characterized by short-term and strong transient operation.This dissertation takes a 300 MVar synchronous condenser as the research object,and studies the transient characteristics,end magnetic field,end structure’s eddy current loss and temperature rise during the fault process of the UHVDC transmission system.The unit-network coupling transient model of large synchronous condenser is established,and the transient characteristics of large synchronous condenser during the short time and continuous fault of the AC voltage at the sending end of the UHVDC transmission system are analyzed.The regulation capability of large synchronous condenser to the AC voltage at the sending end of UHVDC transmission system under different fault levels is studied,and the transient reactive power characteristics and its influencing factors of large synchronous condenser under different faults of transmission system are revealed.By comparing with the measured results,the accuracy of the unit-network coupling transient model of large synchronous condenser is verified.A three-dimensional analytical method is proposed to calculate the magnetic field in the end region and the eddy current loss in the clamping ring of large synchronous condenser.The virtual equivalent current in space is established,taking into account the influence of the stator back core and the rotating shaft on the magnetic field in the end region.Combined with the finite element method,the calculation of the magnetic field in the end region of synchronous condenser and the eddy current loss in the clamping ring is realized,and the influence of the material properties and structural parameters of the clamping ring on the eddy current loss is analyzed.The problems of difficult mesh generation,long calculation time and high requirement of computer configuration in solving the end magnetic field and structure’s eddy current loss of large electrical machines in the early stage of engineering research are effectively solved.The accuracy and efficiency of the proposed method are verified by comparing the calculation results and calculation time with the three-dimensional finite element method.A novel shielding topology and a clamping finger topology are proposed,which can effectively reduce the eddy current loss in the end structure.Three dimensional nonlinear transient electromagnetic field calculation models under traditional structure and new structure are established respectively to calculate the distribution law of magnetic field in the end region and eddy current loss in the end structure under steady and transient operating conditions of large synchronous condenser.The effectiveness of the proposed structure topology is verified by comparing the maximum regions of magnetic flux density and eddy current density in the end structure.A three-dimensional flow-heat coupling calculation model for the end region of large synchronous condenser is established.Combined with the distribution law of eddy current loss in end structure,the sub region grids of end structure are constructed.With the eddy current loss of the sub region as the heat source,and the given fan inlet velocity and outlet pressure as its boundary conditions,the flow-heat coupling field of large synchronous condenser under rated operating conditions is calculated.Analyze the fluid velocity and temperature distribution rule in the end region of the condenser,reveal the relationship between the loss,cooling conditions and temperature rise distribution of the end structure,explore the influence of the proposed end shielding and clamping finger topology on the temperature rise of the end fluid and end structure,and verify with the measured results.更多还原