【作者】 张芳；

【导师】 房大中；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2007， 博士

【摘要】 电网的大规模广域互联和电力市场化使得电力系统的运行点比以往更接近稳定极限,这促使电力工业界研究开发更加有效的稳定控制方法。本文的研究工作围绕着“电压稳定”和“功角稳定”两个经典的研究领域展开,定位于系统的稳定性控制,主要内容概括为基于系统运行状态的电压稳定性控制与基于FACTS控制器的暂态功角稳定性控制。本文取得的主要研究成果如下:提出了最优协调电压紧急控制新模型,新模型考虑了负荷内在动态和控制的连续/离散特性,紧急情况下能够从全局意义上协调位于不同地理位置的不同类型的控制。电压稳定的性能指标采用负荷母线电压偏差的积分形式。基于最优控制原理严格推导了性能指标相对控制的灵敏度(梯度),灵敏度可以通过前向求解QSS时域仿真与后向求解伴随方程得到。新模型具有以下优点:①求解方便:灵敏度的获得使得难于处理的复杂的优化问题转换为易于求解的二次规划问题。②切负荷的合理性:利用灵敏度指导切负荷,具有最大灵敏度的负荷被优先切除,保证了最少的切负荷量。③模型适应性强:新模型基于QSS时域仿真,对系统模型和规模的适应性与时域仿真等同。④在线计算的潜力:一次灵敏度计算时间小于两次QSS仿真时间,而且二次规划的求解速度比现有模型中采用的智能方法快得多。文中还给出了利用模态分析技术沿着QSS不稳定时域轨迹离线选择系统弱母线的方法。提出了考虑电压稳定约束的最优预防控制新方法,与现有预防控制方法相比,新方法不需要沿着系统故障后轨迹鉴别临界点,既能针对故障后系统动态轨迹稳定、但电压不安全的情况实施预防控制,又能针对故障后系统动态轨迹不稳定的情况实施预防控制,具有很强的实用性。新方法不依赖于控制的类型,控制措施可以方便地扩展到其它参数空间。统一潮流控制器(UPFC)是功能最全面的FACTS控制器,最早提出了将控制理论中的相对增益矩阵(RGA)方法应用于分析UPFC多个控制回路之间的耦合程度,从而为UPFC选择了控制回路之间耦合程度最为薄弱的最佳变量配对方案,并且详细分析了运行方式以及振荡频率变化对最佳变量配对的影响。基于RGA方法首次为文献中广为采用的UPFC控制方案提供了严格的理论支持。提出了UPFC直流电容电压的控制策略,基于该策略设计了阻尼联络线低频振荡的UPFC两阶段控制方案,文中还给出了一种利用UPFC安装处的本地可测量信号估算惯性中心之间角速度的方法,估算结果准确、可靠。更多还原

【Abstract】 The large-scale wide area interconnected electric network and deregulated market environment of power systems have driven the operation of power systems closer to their limits than ever, and urge the electric power industry to study and develop more effective stability control methodologies. This thesis involves two classical research fields, namely, voltage and angle stability, and focuses on the power system stability control. The main contents include the voltage stability control based on the operation state of power systems and angle stability control based on the FACTS controller. The following are the main contributions of this thesis.This thesis proposes a novel model for optimal coordinated voltage emergency control. It takes account of the dynamics of loads and discrete/continuous nature of controls with coordination of dissimilar controls at different geographical locations in order to prevent voltage collapse during an emergency. An integration index of the load bus voltage deviation is adopted as the voltage stability performance index.Based on the optimal control theory, the sensitivities (gradients) of this performance index with respect to controls are derived rigorously. The sensitivities can be evaluated by solving the adjoint equations using the fast quasi-steady-state (QSS) time domain simulation results. This novel model has the following advantages: Firstly, the availability of the sensitivity allows the complex intractable voltage optimization problem to be transformed into a classical quadratic programming problem. Secondly, load shedding is guided via the sensitivity information. The ones with higher sensitivity would have the higher priority to shed such that the minimum amount of load shedding can be ensured. Thirdly, this novel model is based on the QSS simulation; therefore it has the same adaptability to the system modeling and scale as the time domain simulation. Finally, the overall computational speed of the novel model is very competitive. Typical computation time of sensitivity is less than two times QSS computation time, and the computation speed of quadratic programming is much faster than the intelligence methods. Moreover, a method to select the buses vulnerable to voltage instability using the modal analysis technique along QSS unstable trajectory is also provided in this thesis.This thesis proposes a novel optimal preventive control methodology with voltage stability constraints. Compared to the existing preventive control methodologies, the proposed novel methodology do not require to identify the critical point along the QSS time domain trajectory of the post-contingency system. It can deal with not only the case that the dynamic trajectory of the post-contingency system is stable but voltages have violation, but also the case that the dynamic trajectory of the post-contingency system is unstable. Since this novel methodology is not dependent on the control type, it is convenient to extend the controls to other parameter spaces.The unified power flow controller (UPFC) is the most versatile FACTS controller, in this thesis the relative gain array (RGA) method in control theory is first applied to analyze the interaction degree among UPFC multiple control channels, and select the best variable pairs for UPFC under which the interaction among UPFC control channels is the weakest. Furthermore, the influences of operation mode variations and oscillation frequency variations on best pairs are analyzed. Based on RGA method this thesis for the first time provides the rigorous theory support for the widely used control scheme of UPFC. Novel control strategies of DC capacitor voltage are then proposed and lead to the design of a novel two-stage control scheme for UPFC to damp tie-line low frequency oscillation. Moreover, an effective estimation method based on the locally measurable quantities is proposed in this thesis to estimate the angular speed difference between centers of inertia (COI), and the estimation result is quite accurate.更多还原