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61.
Juan Segundo‐Ramírez Aurelio Medina Arindam Ghosh Gerard Ledwich 《International Journal of Circuit Theory and Applications》2012,40(6):551-569
In this contribution, a stability analysis for a dynamic voltage restorer (DVR) connected to a weak ac system containing a dynamic load is presented using continuation techniques and bifurcation theory. The system dynamics are explored through the continuation of periodic solutions of the associated dynamic equations. The switching process in the DVR converter is taken into account to trace the stability regions through a suitable mathematical representation of the DVR converter. The stability regions in the Thevenin equivalent plane are computed. In addition, the stability regions in the control gains space, as well as the contour lines for different Floquet multipliers, are computed. Besides, the DVR converter model employed in this contribution avoids the necessity of developing very complicated iterative map approaches as in the conventional bifurcation analysis of converters. The continuation method and the DVR model can take into account dynamics and nonlinear loads and any network topology since the analysis is carried out directly from the state space equations. The bifurcation approach is shown to be both computationally efficient and robust, since it eliminates the need for numerically critical and long‐lasting transient simulations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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根据事故后稳态潮流与它们各自的电压稳定裕度指标的对应关系,提出了一种新的事故筛选指标,并从所有预想事故中筛选出一定数量的事故进入严重事故集,然后用改进连续潮流法求解对应的有功裕度指标并进行排序,极大地提高了事故扫描的速度,可应用于在线电压稳定监测。同时将该方法用于某省网系统的在线电压稳定监测计算,取得了显著的效果。 相似文献
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针对互补集总经验模态分解(complementary ensemble empirical mode decomposition,简称CEEMD)在处理非平稳随机信号时能够有效地消除模态混叠,却仍然存在包络拟合过冲/欠冲和端点效应问题,提出了同伦-最小二乘支持向量双回归(homotopy least squares-support vector double regression,简称HLS-SVDR)的保形分段三次样条(shape-preserving piecewise cubic spline,简称SPPCS)的完备CEEMD改进方法。首先,使用SPPCS插值法消除在构造上、下包络曲线过程中产生的拟合过冲/欠冲问题,获得有效的包络线;其次,使用HLS-SVDR对各层信号极值点的包络均值曲线两端进行左、右预测覆盖以抑制端点效应;最后,将该方法用于滚动轴承的微故障特征提取的实例分析中。实验结果表明,该方法能够更有效地提取滚动轴承微故障特征,实现了一种既保持CEEMD原有特性,同时又能够抑制过冲/欠冲和端点效应的完备CEEMD算法。 相似文献
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地形条件或采集成本等因素往往导致现场采集到的地震数据呈现不完整分布,从而影响后续地震数据的分析与处理,因此对原始地震数据做高精度重建显得尤为必要。不动点延续算法是一种基于核范数最小化的重建方法,但该算法需进行奇异值分解(SVD,其计算复杂度为O[mnmin(m,n)],m、n为矩阵的维度),且当矩阵维度较高时运算耗时较长;传统方法是直接利用PROPACK加速包,将计算复杂度降低为O(rmn)(r为矩阵的秩),但此加速方法依然耗时较长。为此,提出一种快速不动点延续算法,通过利用块克雷洛夫迭代近似奇异值分解算法和子空间复用技术,将SVD的计算复杂度降低为O[mcmin(m,c)](c<m,n),c∈R+)为复杂度常数。仿真地震数据和实际地震数据重建结果表明,在确保一定信噪比的情况下,文中提出的快速不动点延续算法的计算效率显著高于传统加速型不动点延续算法。 相似文献
66.
Large-scale strongly nonlinear and nonconvex mixed-integer nonlinear programming (MINLP) models frequently appear in optimization-based process synthesis, integration, intensification, and process control. However, they are usually difficult to solve by existing algorithms within acceptable time. In this study, we propose two robust homotopy continuation enhanced branch and bound (HCBB) algorithms (denoted as HCBB-FP and HCBB-RB) where the homotopy continuation method is employed to gradually approach the optimum of the NLP subproblem at a node from the solution at its parent node. A variable step length is adapted to effectively balance feasibility and computational efficiency. The computational results from solving four existing process synthesis problems demonstrate that the proposed HCBB algorithms can find the same optimal solution from different initial points, while the existing MINLP algorithms fail or find much worse solutions. In addition, HCBB-RB is superior to HCBB-FP due to much lower computational effort required for the same locally optimal solution. 相似文献
67.
A directional control method (DCM) for power flows on a set of interface lines between two regions of power system considering static voltage stability margin is developed in this paper. A surface approximation approach is firstly used to obtain the relationship between the interface flow solution and the generation direction of generator (the portion of generation variation in each participating generator to satisfy the desired power increase on the interface and the system loss). Then, an optimization model is built to determine the optimum dispatching scheme of generators. This method not only can control the total power on the interface to satisfy the power demand but also can realize the directional control of power on each interface line based on the needs of operation. The proposed DCM is further extended to determine the optimum dispatching scheme of generators for maximizing the interface flow margin (IFM), which is the active power margin of the key transmission lines between two regions of power system constrained by static voltage stability. A modified continuation power flow (MCPF) is used to show and evaluate the impacts of the DCM on the IFM. The New England 39-bus system and the IEEE 300-bus system have been employed to verify the effectiveness of the DCM. 相似文献
68.
Two‐Parameter Continuation and Bifurcation Strategies for Oscillatory Behavior Elimination from a Zymomonas mobilis Fermentation System
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Ibrahim H. I. Mustafa 《化学工程与技术》2015,38(8):1362-1370
Two‐parameter continuation and bifurcation analysis strategies were applied to deal with the oscillatory phenomena of a Zymomonas mobilis ethanol fermentation system. A structured verified non‐linear mathematical model considering the physiological limitations of microorganisms for a single continuous fermenter for ethanol production using Z. mobilis was built to identify the Hopf bifurcation (HB) points, which indicate the oscillatory behavior, using the inlet substrate concentration and the dilution rate as bifurcation parameters. The path of the HB points can be determined with different controlling operating parameters. It was found that with the addition of a small amount of cells or ethanol to the feed stream or by increasing the dilution rate, the oscillations could be eliminated and steady‐state behavior was attained. Using a two‐parameter continuation strategy, the Z. mobilis fermentation system could operate at steady state without oscillatory behavior. 相似文献
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