【作者】 徐衍会；

【导师】 贺仁睦；

【作者基本信息】 华北电力大学（北京） ， 电力系统及其自动化， 2010， 博士

【摘要】 国内外电力系统多次发生机网相互作用导致的发电机组损坏或者电网失去稳定。随着我国“西电东送”战略的实施,发电机组经电网远距离大功率送电成为一种普遍模式。随之带来的问题一是系统中多次发生机理不明的低频功率振荡,二是为了提高输电能力采用串补或高压直流输电使得次同步振荡问题突出。在我国电力体制改革实施厂网分开以后,发电机组和电网隶属于不同的电力集团。因此,保障发电机组的安全与保证电网稳定运行的矛盾亟需解决。深入分析与评估电力系统机网动态过程是保证大机组与大电网安全稳定的基础。本论文从刚体运动稳定性角度分析电力系统机网动态过程。首先根据单刚体运动稳定性理论,通过建立机网耦合模型与数字仿真平台,分析了调速系统扰动对电力系统小信号稳定性的影响。仿真结果表明,当调速系统扰动频率与电力系统自然振荡频率接近时将导致系统出现等幅值的低频功率振荡。然后从多刚体运动稳定性理论出发,采用机组作用系数法和复转矩系数法分析了HVDC引起的次同步振荡,并设计了次同步振荡阻尼控制器,通过仿真验证了SSDC抑制次同步振荡的有效性。对多刚体运动稳定性边界进行了研究,改进了多刚体轴系模型。应用互补群群际能量壁垒准则分析了我国漳泽发电厂的轴系扭断事故。研究表明互补群群际能量壁垒准则能够计及故障后机网间的能量交换,适用于非自治轴系扭振的稳定性分析。针对发电机组轴系参数不准确的问题,采用不确定参数的简单集中质量模型来描述汽轮发电机组轴系。计算了特征值对轴系参数的灵敏度,灵敏度大的轴系参数的改变对次同步振荡的仿真结果具有显著影响。应用概率分配法简化了轴系参数不确定性与轴系各质量块之间扭矩的关系。研究表明,轴系参数的不确定性引起了次同步谐振较大的不确定度；本文设计的SSDC在轴系参数不确定性情况下仍然能有效地抑制次同步振荡。从材料力学出发分析轴系失稳的机理,提出了一套次同步振荡对轴系作用的评估方法：当轴系所受到的最大剪切应力超过强度极限时,轴系将被破坏；当剪切应力低于强度极限而高于疲劳极限时进行疲劳损伤计算。对于变幅值的次同步振荡通过雨流法将其分解为一系列等幅值的振荡波形,再根据轴系S～N曲线计算疲劳损伤。当疲劳累积利用系数达到1时,轴系消耗100%的寿命,将以疲劳失效而被损坏。通过IEEE第一基准模型的SSR算例和HVDC引起的SSO算例,表明了本论文提出的次同步振荡对轴系作用的评估方法的有效性。更多还原

【Abstract】 The generating unit damage or instability of power grid resulting from the interaction of generating unit and power grid often occurs in domestic and overseas power system. The long-distance high-power transmission of generating unit through power grid has become a prevalent mode as the implementation of "West Electricity East Transmission" policy in China. As a result, one problem is low frequency oscillation of inexplicit mechanism often occurs, the other is subsynchronous oscillations (SSO) stand out as the application of series capacity compensation and HVDC transmission line. The generating unit and power grid belong to different power group after the innovation of power system in China. So the inconsistency between protecting generating unit from damage and ensuing power grid stability desiderates to be solved. Analyzing thoroughly and evaluating the Unit-Grid dynamic process of power system is the foundation of ensuing the security and stability of large generating unit and power gird.The Unit-Grid dynamic process is analyzed from the rigid body motion stability point of view in this paper. Firstly, according to the theory of single-rigid body motion stability, the effect of governor system disturbance on power system small signal stability was analyzed through putting up the Unit-Grid coupling model and digital simulation platform. Simulation results indicate that the constant amplitude low frequency oscillation will occur when the frequency of disturbance from governor system is near to the natural frequency of power system low frequency oscillation. Whereafter, according to the theory of multi-rigid body motion stability, the subsynchronous oscillation was analyzed by complex torque coefficient method. The subsynchronous damping controller (SSDC) was designed and the validation of SSDC was proved by simulation. The stability boundary of multi-rigid body motion was researched and the turbine-generator shaft model was improved. Shaft damage of Zhangze power plant was analyzed using Complementary Cluster Energy Base Criteria (CCEBC). Simulation result indicates that CCEBC is an effective method on stability analysis of heteronomy shaft torsional vibration because it can consider the Unit-Grid energy exchange after fault.For the inaccurateness problem of shaft parameter, the uncertainty shaft parameter model was adopted to describe turbine generator shaft. The shaft parameter sensitivity for eigenvalue was calculated. The change of shaft parameter with large sensitivity has distinct influence on simulating subsynchronous oscillation. The Probabilistic Collocation Method (PCM) was adopted to simplify the relationship between the uncertainty in shaft parameter and the oscillations of shaft system. Shaft parameter uncertainty will result in high uncertain degree and the SSDC designed in this paper can effectively damp SSO even if the shaft parameter is uncertain.The mechanism of shaft damage was analyzed basing on material mechanics theory. The evaluation method about the effect of SSO on turbine generator shaft was put forward. If the cut stress exceeds intensity limit, the shaft will be destroyed. If the cut stress is between intensity and fatigue limit, the fatigue damnification should be calculated. By applying rainflow algorithm, the SSO of variational amplitude was decomposed into a series of costant amplitude SSO. And then, the fatigue damnification was calculated according to the shaft S-N curve. If the fatigue comulation coefficient is equal tol, the 100 percent life of shaft will be used up. Consequently, the shaft will be destroyed due to fatigue invalidation. The validity of the evaluation method about the effect of SSO on turbine generator shaft was shown through the subsynchronous resonance of IEEE first benchmark model and subsynchronous oscillation induced by HVDC examples.更多还原