A probabilistic load shedding concept considering highly volatile local generation

Automatic load shedding is the ultimate countermeasure against imbalance in a power system and can effectively help preventing large blackouts. Taking into account a high penetration of renewable energy sources (RES) in the distribution grid, a clear distinction between load and generation at the PCC becomes increasingly more difficult. For that reason an adaptation of frequency relay parameters and their locations of installation are necessary. In Europe this is rest on a multi-step plan based on values such as the yearly peak load. In this paper a novel probabilistic method for automatic load shedding is presented that uses the average values instead of peak values for load shedding. Its applicability is verified by a dynamic power system model that was developed to compare the classical and novel probabilistic load shedding principle. The method is verified using data from a German TSO.     

A simple model for deep dynamic stall conditions

The present study is focused on modeling of dynamic stall behavior of a pitching airfoil. The deep stall regime is in particular considered. A model is proposed, which has a low implementation and computational complexity but yet is able to deal with different types of dynamic stall conditions, including those characterized by multiple vortex shedding at the airfoil leading edge. The proposed model is appraised against an extensive data set of experimental (α,C_L) curves for NACA0012. The results of an existing widely used model, having comparable complexity, are also shown for comparison. The proposed model is able to well reproduce not only the classic curves of deep dynamic stall but also the curves characterized by lift oscillations at high angles of attack due to the shedding of multiple vortices. Furthermore, the model appears to be robust to variations of its parameters from the optimal values and of the airfoil geometry. Finally, the model is successfully implemented in a commercial CFD software and applied to the simulation of a vertical axis wind turbine within the actuator cylinder approach. The accuracy of the prediction of the turbine power coefficient in the whole rotation cycle is very good for the optimal working condition of the turbine, for which the model parameters were calibrated. Fairly good accuracy is also obtained in significantly different working conditions without any further calibration.     

嵌入式数字智能涡街流量计的设计开发

针对目前涡街流重计存在精度不高的问题，采用Toeplitz自相关矩阵近似的准牛顿算法，对涡街传感器输出信号进行数字信号处理。针对客户超低功耗的要求，开发设计以超低功耗的混合信号处理器(MSP430F149)为微处理器，以采用KS0713为控制器的LCD为液晶显示模块，符合HART总线协议的嵌入式智能涡街流量计。     

高雷诺数下双圆柱绕流的数值模拟

本文使用表面涡法研究高雷诺数下不同排列方式双圆柱绕流的流动状态，计算了双圆柱在并列、串列及级列的情况下的各种流动结构，涡街的变化及作用在圆柱上的受力情况。本文结果清楚地描述了双圆柱绕流复杂的流动状况，计算结果与实验显示的流动状况十分相似，斯特罗哈数和阻力系数与实验结果符合得很好。     

三峡水电站ALSTOM机组低水头运行稳定性分析

混流式水轮机的水力稳定性与机组水力工况密切相关。以三峡电站左岸6号机组稳定性试验为例，分析了ALSTOM机组的低水头运行稳定性。根据试验分析结果，可将机组运行工况划分为小负荷区、涡带振动区、大负荷运行区。小负荷区机组效率较低，机组不宜在此区间运行；大负荷区机组运行稳定性最佳，但机组应避开强涡带工况区和特殊频率振动区运行。     

Wake and aerodynamics loads in multiple bodies—application to turbomachinery blade rows

Two-dimensional, unsteady flow around bodies of complex geometry (or multiple bodies) at high Reynolds number is simulated using the vortex method. This method is modified to take into account the sub-grid scale phenomena through a second order velocity structure function model adapted to the Lagrangian scheme. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm; the convection process is carried out with a Lagrangian Adams-Bashforth time-marching scheme and the diffusion process is simulated using the random walk method. The pressure distribution is obtained using an integral equation derived from the pressure Poisson equation, which was first developed for a single body. Results for the numerical simulation around a linear cascade of airfoils are presented. As the flow is periodic in the y direction, the discrete vortex shedding need only be considered for a reference airfoil. The flow characteristics around the NACA 65-410 series airfoils are calculated and comparisons are made with results available in the literature.     

FLOW OF NEWTONIAN FLUIDS THROUGH SINUSOID ALLY CONSTRICTED TUBES. NUMERICAL AND EXPERIMENTAL RESULTS

Numerical and experimental predictions of pressure drops in the flow of Newtonian fluids through sinusoidally constricted tubes (SCT) are carried out. The numerical evaluations analyzed in this work are obtained from the following methods: Geometric Iteration (GJM), Geometric Iteration with First and Second Upwinds (GIM1, GIM2), Successive Over Relaxation by Line (SORBLM), Global Galerkin Spectral Method (GGSM), Collocation (CM) and Dufort-Frankel (DFM). The GIM1, GIM2 and SORBLM are applied to SCT and explained in this work. The other methods have been previously reported in the literature with the same purpose. Experiments are accomplished for constrictions of approximately 40,60 and 80% of the average tube diameter and results compare well with numerical predictions of the steady flow. It is concluded that special attention should be given to evaluations of the friction factor ƒ for Reynolds numbers Re between the onsets of flow separation and turbulence due to flow instability. Finally, the SCT as a model for porous media (PM) is discussed.     

盆池涡涡动过程数值研究

盆池涡是在盆池排水时在盆池中央的排水管道入口处形成的漏斗状旋涡。文中采用标准κ-ε湍流模型和VOF方法对盆池涡的涡动全过程进行了仿真模拟，然后对计算结果进行分析和归纳，提出了盆池涡涡动机理假说。盆池涡是由外来扰动或流道截面几何形状的不规则或表面粗糙度不均匀引起速度场一定的切向流动而诱发出来的旋涡，其旋转方向是随机的，但与形成的切向流动方向一致。盆池涡是一种类兰金涡，速度和压力的分布具有兰金组合涡的特点；盆池涡在成熟阶段具有三个特性区域，分别称为抽气孔、吸气孔、抬气区域。     

涡流管类比逆流换热器方法的研究

结合Scheper，Lewins和Bejan的理论模型，对涡流管类比逆流换热器模型进行了深入地分析，得出了冷流分量对温度分离效应的函数关系式，为了解涡流管机理和实验中强化涡流管温度分离效应提供了理论依据。