【作者】 孙闻；

【导师】 房大中；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2010， 博士

【摘要】 电力系统的安全稳定运行是保证可靠供电的基础,暂态稳定问题是电力系统稳定性研究的一个重要方向,研究人员一直致力于发展快速、有效的暂态稳定分析与控制方法,并取得了一定的进展。随着计算机技术的发展,实现对电力系统的在线暂态稳定分析成为可能,本文提出了一种适用于在线应用的暂态稳定分析与控制方法。论文首先提出了投影能量函数理论,该理论在归一化能量函数的基础上发展而来,其原理是通过投影变换,将故障后电力系统的动态过程比拟为相点在旋转一维坐标轴上的运动,假设相点具有单位质量时,其在旋转一维坐标轴上的动能和势能定义为投影动能和投影势能。投影能量函数克服了归一化能量函数回摆时刻最小动能不为零的缺点,通过研究故障后系统最小投影动能与故障切除时间的关系,提出了快速估算有危害故障临界切除时间的方法。基于投影能量函数理论,建立了一整套电力系统在线安全分析策略,包括新型的功角稳定判据、反映有危害故障的严重程度的暂态稳定指标和调度员辅助决策算法。在上述理论和方法的基础上开发了天津电网稳定在线监视评估系统,该系统可以实现对电网的暂态稳定性的实时监控和预警,让调度人员能够及时了解系统运行中存在的稳定问题。利用轨迹灵敏度计算方法求解不稳定故障的最小投影动能对发电机有功输出的灵敏度,结合迭代的方法,计算暂态稳定约束下严重受扰机组的有功输出极限。在此基础上,研究发展了一种考虑暂态稳定约束的电力系统最优潮流算法,通过对有危害故障进行分析,计算相关发电机的有功输出极限,将暂态稳定约束转化为发电机有功出力约束,使含暂态稳定约束的最优潮流问题可用传统的方法求解。基于电力系统角半径的概念,定义了暂态稳定控制性能指标,通过求取其对发电机有功输出的灵敏度,将暂态稳定约束近似线性化,作为不等式约束加入以调整成本最小为目标函数的有功安全调度优化模型中,并设计了一套迭代的方法计算发电机有功出力的最佳调整方案。文章将暂态稳定约束引入阻塞管理问题中,在解决传输阻塞的同时,还能提高系统对大扰动的承受能力,对维持电力系统的安全运行有重要意义。更多还原

【Abstract】 Power system security and stability is the precondition of reliable power supply. Transient stability analysis is evaluation of the ability of systems to withstand specified contingencies and to survive the subsequent transient events to arrive at an acceptable steady operating condition. Researchers have been working for a fast and effective method for transient stability analysis and control and remarkable progress has been achieved. This paper tries to develop a new method for transient stability analysis and control for online application.On the basis of normalized energy function (NEF) theory, a novel concept of projection energy function (PEF) is proposed. By projection transformation, the power system dynamic in post fault duration is studied on the rotation coordinates axis. PEF overcomes the drawback of NEF that the total normalized kinetic energy only becomes minimum but not zero even though the system is stable. The variation characteristic of the minimum of projection kinetic energy (PKE) in the post-fault duration for a contingency versus fault clearing times has been studied. Based upon the above characteristic, a new way to assess critical clearing time of unstable contingency is developed.An approach for online transient stability analysis, which includes a new angle instability criterion, stability index for harmful contingency and operation mode adjustment algorithm, is proposed. Using the theory of PEF, software for online transient assessment of Tianjin power grid is developed, which provides real-time monitoring and can help the operators to find out the weakness point of the power system.The trajectory sensitivity mapping technique is utilized to evaluate the gradient of minimum PKE with respect to active power output of generators. Using the gradient, a new approach for stability-constrained generation limit assessment is proposed to develop a method for optimal power flow with transient stability constraints (OTS). Then the stability constraints represented by differential equation are converted into inequality constraints of active power outputs of generators. Thus, the OTS problem could be solved by traditional optimal power flow (OPF) method.The idea of angle norm has been introduced to develop a novel transient stability performance index. The sensitivity of the performance index relative to mechanical power input of the generators can be calculated by trajectory sensitivity method. With the sensitivity, the system stability constraints imposed by unstable contingencies are expressed by linear inequalities. Then a new generation security dispatching approach is presented for transient stability enhancement of power systems, which can optimally reallocate power generations for multiple unstable contingencies. The transient stability constraints are also introduced to congestion management. Under this framework, the generators participated in dynamic congestion management are dispatched on the principle of maintaining the possible adjustment at least cost as well as submitting thermal limit and transient stability constraints.更多还原