基于Saber的交流励磁发电机励磁电源仿真研究

根据单机等面积稳定判据原理,把发电机功角曲线展开成自变量为功角的高阶泰勒级数,采用时域仿真的办法对受扰系统进行短时间的仿真,根据仿真结果对机组电磁功率与转子相对角曲线进行拟合。用得到的功角曲线预测机组的最大减速面积之差,从而可以计算出系统的稳定裕度与不稳定裕度。采用的单机等面积技术既具有时域仿真方法的精确性与良好的适应性,又能适用于大规模电力系统,可得出基于加速面积与减速面积的能量型稳定裕度。与其它能量函数法相比,该方法不必进行失稳模式的判别。实例计算表明所提出方法能充分满足工程应用中的可靠性、有效性和计     

暂态稳定分析中的发电机电磁功率预测研究

在二群失稳模式下 ,得出了机组电磁功率与转子相对惯性中心角的变化为正弦曲线。根据单机等面积稳定判据原理 ,采用时域仿真的办法对受扰系统进行短时间的仿真 ,根据仿真结果对机组电磁功率与转子相对角正弦曲线进行拟合 ,从而得到故障后发电机电磁功率曲线。与传统的用发电机与网络实时参数计算所得的电磁功率方法相比 ,不必进行详细长时间仿真 ,而所得到的预测值与实际计算所得值误差在± 5 %以内 ,且所得到的表达式是具有物理解析意义的。实例计算表明所提出的方法速度快且精度高 ,具有广泛的工程应用前景     

基于功角曲线拟合的快速暂态稳定预估分析

提出了一种基于可编程逻辑门阵列（FPGA）的适用于电力系统的三相锁相环（PLL）的优化设计与实现方案。首先介绍了包括鉴相器、环路滤波器和压控振荡器等在内的锁相环基本结构和工作原理,然后利用模块化的设计方法利用VHDL语言设计了这些模块。为了尽量节省逻辑资源,在利用FPGA实现该锁相环的过程中,采用了面积共享的优化设计方案;同时提出了一种新的正弦函数产生方法,该方法将CORDIC算法和查表法相结合,这样既保证了数值的精度,又提高了运算速度。该锁相环在Altera公司Cyclone EP1C12Q240C8芯     

单机等面积法电力系统暂态稳定分析

根据单机等面积定则原理SGEAC(single generator equal area cirterion)对基于动态单等值机群的稳定裕度与基于动态二等值机群相对运动的稳定裕度进行了比较研究,发现两者完全一致.利用物理系统多变量函数的高阶导数,得到了单一等值机群与单一机组功角曲线的理论表达方式,由时域仿真与曲线拟合得到单一机群或单一机组的功角曲线,最终得到系统的能量型稳定裕度.实例验证了所提方法的有效性.     

以单机等面积稳定判据分析多机系统暂态稳定性

结合时域仿真，提出了多机系统中单机角度加速面积、减速面积与单机时间加速面积、减速面积的计算方法；由发电机转于运动微分方程求解得出的转于角速度的计算公式和对稳定系统与不稳定系统发电机转于角速度变化的观察，得出了多机系统中单机等面积稳定判据。单机加速面积、减速面积的计算中考虑了多机的相互影响，揭示了多机稳定系统中单机加速面积与其减速面积是相等的。提出了临界机组的筛选方法。系统临界机组群单机等面积稳定判据与时域仿真角度准则具有相同的精度，但具有数值积分时间短的优点。     

基于稳定裕度指标的暂态电压稳定分析

基于稳定域边界二次近似,提出了暂态电压稳定裕度指标,并分析了计及感应电动机机电暂态过程的单负荷无穷大系统的暂态电压稳定性.仿真表明:该指标具有准确度高及易于计算机实现等特点,具有较好的工程实用性,并可应用于判断系统暂态电压稳定裕度和估计暂态电压稳定的临界切除时间以及故障排序.     

无功调控对暂态功角稳定性的影响

单机无穷大系统和实际电网的仿真算例表明,在发电机有功出力不变的情况下,通过增加临界群发电机组的无功出力可提高电力系统的暂态功角稳定性和输电功率极限。运用等面积法则对其机理进行详细分析并得出结论:增加发电机的无功出力对系统功角稳定的影响随故障切除时间的改变而改变,当在故障后的恢复曲线高于初始机械功率时,其对功角稳定的影响效果明显,并随着故障切除时间的延迟将逐渐增大,而切除时间很短时,增加发电机无功的初始出力对系统功角稳定的影响并不大。仿真结果证明了其正确性和合理性,从而为电力系统的稳定运行提供了一种灵活的控制手段。     

一种计及暂态稳定约束最优潮流的快速方法

给出了一种求解暂态稳定约束下最优潮流(OTS)的快速方法.在该方法中,首先将势能边界面法与最小二乘法相结合,建立系统暂态稳定裕度与系统运行参数变化之间非线性关系的函数表达式;然后基于该函数表达式形成暂态稳定约束条件引入到常规最优潮流(OPF)模型中,从而形成OTS问题的数学模型.该文建立的OTS分析方法不仅使得OTS的求解规模与常规OPF相同,而且计算量亦与常规OPF基本一样.对新英格兰10机39节点典型系统的算例仿真表明了该OTS分析方法的有效性.     

一种计及暂态稳定约束最优潮流的快速方法

给出了一种求解暂态稳定约束下最优潮流(OTS)的快速方法。在该方法中,首先将势能边界面法与最小二乘法相结合,建立系统暂态稳定裕度与系统运行参数变化之间非线性关系的函数表达式;然后基于该函数表达式形成暂态稳定约束条件引入到常规最优潮流(OPF)模型中,从而形成OTS问题的数学模型。该文建立的OTS分析方法不仅使得OTS的求解规模与常规OPF相同,而且计算量亦与常规OPF基本一样。对新英格兰10机39节点典型系统的算例仿真表明了该OTS分析方法的有效性。     

暂态功角弱稳定模式辨识及其协调紧急控制策略

针对电网发展过程中可能出现的复杂暂态功角失稳现象,提出了用于系统安全稳定分析和控制的暂态功角弱稳定模式的概念及其辨识方法,解析了紧急控制导致弱稳定模式演化为主导失稳模式的机理及其近似必要条件。在理论分析的基础上,提出了基于系统暂态稳定约束转化的紧急控制数学模型,进而设计了基于动态灵敏度指标的启发式协调紧急控制策略计算方法,提升了紧急控制算法对于处理复杂暂态失稳情况的适应性,实现了统筹系统暂态功角多个弱稳定模式的自动协调控制。基于实际电网的算例验证了所提紧急控制负效应机理及策略搜索算法的有效性。     

一种简捷快速的暂态稳定仿真算法

在对Taylor级数法暂态稳定计算的步长进行分析的基础上,根据计算精度的要求,提出了Taylor级数法暂态稳定计算步长的动态控制,并由此实现了一种简捷、快速的暂态稳定计算方法.分析与计算结果表明,由于在计算过程中按计算精度的要求来动态地选取步长,从而在保证计算精度的前提下,有效地提高了Taylor级数法暂态稳定计算的解算效益.     

一种简捷快速的暂态稳定仿真算法

在对Ｔａｙｌｏｒ 级数法暂态稳定计算的步长进行分析的基础上,根据计算精度的要求,提出了Ｔａｙｌｏｒ 级数法暂态稳定计算步长的动态控制,并由此实现了一种简捷、快速的暂态稳定计算方法。分析与计算结果表明,由于在计算过程中按计算精度的要求来动态地选取步长,从而在保证计算精度的前提下,有效地提高了Ｔａｙｌｏｒ 级数法暂态稳定计算的解算效益。     

A simple direct method for fast transient stability assessment oflarge power systems

A method for online transient stability assessment of large power systems is proposed. It consists of: replacing the multimachine system by a two-machine dynamic equivalent, further amenable to a one-machine-infinite-bus system; reducing the stability problem to a sole algebraic equation, devised from the equal area criterion, or equivalently from the Lyapunov direct criterion; and using this equation to derive one-shot stability analysis strategies. A technique for system admittance matrix reduction is developed that proves efficient, especially for large systems and multiple-contingency evaluation. The method's main appeal is rapidity: it is about one order of magnitude faster than the most efficient direct criterion. Other attractive features are flexibility and ability to encompass various simulation conditions. Extensions to online sensitivity analysis and control are suggested     

A fast approach to transient stability estimation using an improved potential energy boundary surface method

In this paper, a new fast algorithm to perform online transient stability assessment (TSA) in a power system is proposed. The TSA is concerned with finding the critical clearing time (CCT), the stability limit, for a specified fault. The method possesses the merits of the fast speed of the potential energy boundary surface method and the accuracy of the conventional time domain simulation technique. To expedite the algorithm, an efficient stopping criterion for postfault trajectory simulation is developed. Examples are given to show the problems of integration stopping criteria published in recent papers and how they are tackled. Extensive test results on several systems, including the 10-generator New England system, the 17-generator Iowa system and the IEEE 50-generator system, are reported.     

A new method for transient stability analysis

This paper proposes a brand‐new method for transient stability analysis in power systems. The proposed method directly computes the critical trajectory for a given contingency to obtain the critical condition of the studied system. Although the method may be useful for general nonlinear dynamic systems, it is applied to the problem of obtaining a controlling UEP, unstable equilibrium point, which provides inevitable information for the energy function methods to assess transient stability. Namely, the proposed method effectively yields a critical trajectory on PEBS together with the controlling UEP, thus improving the conventional BCU method. The effectiveness of the proposed method is demonstrated in 3‐machine 9‐bus and 6‐machine 30‐bus systems. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 26–33, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20245     

A method of predicting transient constants of synchronous machines

It is difficult to determine the subtransient (transient) reactance and subtransient (transient) short-circuit time constants of medium and large synchronous machines by the sudden three-phase short-circuit test because large-capacity equipment is required. This paper describes a new method of measuring these constants by means of a simple test using a small dc power supply. The key points of this method are as follows. (1) A dc voltage is applied to the armature winding (two terminals with the third one open) of a stationary synchronous machine through a resistance. When the two terminals are closed, the winding is short-circuited and the current in the armature winding decays. The whole process of decaying current is recorded. (2) The value of the transient phenomena of the winding calculated from circuit equations (armature, field winding and damper winding circuits) is compared with actual data, and the unknown equivalent circuit constants are identified by the least squares method. (3) Transient phenomena of the sudden three-phase short-circuit are calculated by the two-reaction theory using identified constants, and, hence, these constants are calculated. The transient constants of synchronous machines obtained by the new method agree closely with the observed values.     

A fast numerical algorithm for transient stability studies of power systems

A fast numerical solution of a technique for improving the speed of the transient stability solution of power systems is presented in this paper. The system is described by a set of first-order differential equations which consist of both linear and nonlinear parts. The linear set of equations is considered separately and is solved by modal analysis using closed-form solutions. The nonlinear part of the equations is solved by a numerical method. As explicit solutions are available for the linear part of the equations, the solution time is considerably reduced. The proposed technique is employed for computing the transient stability of a sample power system represented in detail. A comparison is made with a conventional solution procedure.     

A method of transient stability estimation for power systems by lyapunov function

The power system stability problem has been one of the major subjects concerning power system engineering, and is becoming much more significant today due to the increasing size and complexity of interconnected power systems. In this problem, it is well known that the direct method of Lyapunov is the most suitable method of on-line transient estimation for power systems, and several different techniques have been proposed for the construction of functions up to this time. However, the effectiveness of these Lyapunov functions for power systems have been demonstrated using only digital computer simulations. The purpose of this paper is to construct a microprocessor-based, on-line, transient-stability estimation system using the Lyapunov function constructed by the Lagrange-Charpit method, and to estimate the transient stability of an alternator connected to a large system. The experimental results show that this system can act satisfactorily for estimating the transient stability of the power systems.     

An ANN-based load model for fast transient stability calculations

Load models play an important role in the simulation and calculation of power system performance. This paper presents a new load model which is based on a particular form of artificial neural networks we call adaptive back-propagation (ABP) network. ABP has can overcome some of short-comings of common back-propagation (BP) and ABP load models offer many advantages over traditional load models as they are non-structural and can be derived quickly. The application of the method in modeling loads is illustrated using actual field test data. The load models so obtained are shown to replicate the test measurements more closely than that based on traditional load models. Further extension of the method for the identification of the parameters of the traditional load models is proposed. It is based on linear back-propagation (LBP) network. The proposed LBP load model is incorporated in a transient stability program to show that the computational time is significantly reduced.