基于VMD技术与混合储能策略的风电并网控制方法

针对风电功率波动性和随机性给电网稳定运行带来的不利影响,提出一种基于风电功率变分模态分解(variational mode decomposition,VMD)技术和混合储能系统的风电并网控制策略.首先,对典型风电出力场景的原始功率进行变分模态分解,根据风电并网功率波动标准将原始功率分解为并网功率和储能功率,在平抑风电...     

斯特林发动机振动信号分析及谱估计

为了检测斯特林发动机运行状态,针对斯特林发动机在运行过程中振动信号产生机理,采用了经验模态分解与自回归模型相结合的方法对振动信号进行分析,设计了振动检测系统.通过选取故障信息的本征模函数进行功率谱估计,提取滚动轴承故障特征.测试结果表明:经验模态分解可自适应地分解非平稳信号,生成的本征模函数可提取信号内在的本质特征.对自回归模型进行功率谱估计,提取振动状态异常信号.经实验验证,故障情况与真实异常状况吻合,可有效检测斯特林发动机运行过程中的故障特征.     

基于功率调整与随机接入联合优化的 RFID多读写器抗干扰算法

提出了一种集随机接入和功率控制于一体的多读写器抗干扰联合优化算法,可根据读写器密度自适应调节2种作用的权重.首先全面考虑接入概率、功率大小和信道选择对读写器信噪比的影响,将多读写器抗干扰问题建模成混合-整数规划问题;其次采用广义Benders分解方法将算法分解成易求解的子问题和二进制规划主问题,并证明了算法收敛于全局最优解;最后通过仿真验证了算法在标签识别率和公平性方面优于现有方案.     

OFDM双向中继子载波配对与功率联合优化

为了提高基于正交频分复用(OFDM)的放大转发模式下双向中继系统总容量,提出了一种低复杂度的基于信道增益排序子载波配对算法(SP-SCC)和一种联合该子载波配对与功率分配的资源优化策略. 该策略首先是在等功率的条件下进行SP-SCC方法的子载波配对; 然后在系统总功率的限制下,利用对偶分解获得各子载波间的功率分配; 最后将各子载波上的功率分配到各节点上,即获得了各节点上最优功率分配. 仿真结果表明,所提的资源分配策略可以提高系统总容量.     

一种滤波集成型Gysel功率分配器的设计与实现

为了提高功率分配器对无用信号的抑制能力,针对Gysel功率分配器的结构特征,提出在其基础上实现滤波集成的简明普适思路. 设计完成了具有滤波特性的Gysel功率分配器. 根据奇偶模电路分析方法进行电路分解,获得了易于分析的奇偶模等效电路;利用导纳矩阵求解出端口导纳和阻抗,给出了端口S参数的表达式,并分析了该滤波集成型Gysel功率分配器的电路特性. 通过多个仿真实验案例验证了理论分析结果的正确性. 实验结果表明,该Gysel功率分配器在第5代移动通信系统核心频段的端口反射系数幅值均小于-10 dB,中心频率处的隔离度为17.38 dB,具有较好的带外抑制特性.     

一种协作多点多用户通信系统的预编码方法

提出了新的线性预编码方法,适用于联合处理模式下的协作多点多用户多输入多输出下行链路传输系统. 该方法通过信道矩阵的扩展,引入低复杂度的矩阵分解方法,有效抑制了噪声和多用户干扰这2个因素对系统的影响,并适用于接收端各用户配置任意根天线的系统;提出了在基站总功率受限的约束条件下次优的功率分配方案. 通过对算法复杂度的分析和性能仿真可知,所提方法不仅从总体上降低了中央控制站的处理复杂度,而且改善了系统性能.     

小波分析在AR模型重构路面不平度中的应用

针对线性滤波器AR模型重构路面不平度时低频处误差较大的问题,提出利用小波分析的时频特性来调整重构的路面随机序列。首先根据等级路面的功率谱利用AR模型构造C级路面随机序列,然后利用小波分析的小波分解方法和小波包分解方法对路面随机序列进行分解,根据信号能量与信号振幅平方成正比原理,调整信号分解分量各频段的振幅后再进行信号重构,并在时域和频域上与原信号进行对比。仿真结果表明,小波分解方法和小波包分解方法都能提高重构路面功率谱与目标功率谱的拟合精度,且小波包分解方法在处理高频分解分量时更具优势。     

基于功率成本的中继系统最优功率分配

为了降低移动通信网络的功率成本,依据不同的供电方式所确定的不同功率价格,提出了以功率成本为约束条件,以最小中断概率为优化目标的中继系统最优功率分配方法. 主要采用拉格朗日乘子法求解功率分配结果. 仿真结果表明,当各节点功率价格不同时,基于功率成本的最优功率分配与不考虑功率价格的最优功率分配相比,在中断概率相同的条件下,功率成本较小;当各节点的功率价格相差较大时,对比效果更加明显.     

梁结构中振动功率流的测量研究

研究了梁结构中的振动功率流,给出了梁中振动功率流的一般测量方法,并对实验研究结果进行了分析,研究结果表明,可以根据“无限梁”的速度导纳测量梁中的输入振动功率流。     

旋转填料床的功率实验分析

简介旋转填料床功率分析的相关文献,提出简易测试旋转填料床功率的方案,主要介绍了旋转填料床的两种结构,测试气、液流量及转速对功率的影响,对实验结果进行了分析,总结能耗特点,并从减少能耗的观点出发提出了设计建议.     

Choice of reference surfaces for machined surface roughness in milling of SiC_p/Al composites

In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.     

Application of artificial intelligent systems for real power transfer allocation

The application of various artificial intelligent（AI） techniques,namely artificial neural network（ANN）,adaptive neuro fuzzy interface system（ANFIS）,genetic algorithm optimized least square support vector machine（GA-LSSVM） and multivariable regression（MVR） models was presented to identify the real power transfer between generators and loads.These AI techniques adopt supervised learning,which first uses modified nodal equation（MNE） method to determine real power contribution from each generator to loads.Then the results of MNE method and load flow information are utilized to estimate the power transfer using AI techniques.The 25-bus equivalent system of south Malaysia is utilized as a test system to illustrate the effectiveness of various AI methods compared to that of the MNE method.     

A novel stabilization approach for small signal disturbance of power system with time-varying delay

Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.     

A hardware-based algorithm for virtual machine provisioning in a private cloud

Cloud computing is becoming a key factor in the market day by day. Therefore, many companies are investing or going to invest in this sector for development of large data centers. These data centers not only consume more energy but also produce greenhouse gases. Because of large amount of power consumption, data center providers go for different types of power generator to increase the profit margin which indirectly affects the environment. Several studies are carried out to reduce the power consumption of a data center. One of the techniques to reduce power consumption is virtualization. After several studies, it is stated that hardware plays a very important role. As the load increases, the power consumption of the CPU is also increased. Therefore, by extending the study of virtualization to reduce the power consumption, a hardware-based algorithm for virtual machine provisioning in a private cloud can significantly improve the performance by considering hardware as one of the important factors.     

高可靠性半导体激光器电源的设计

针对半导体激光器易受大电流冲击而性能失效这一问题,报道一种基于"n+1"冗余并联结构的高可靠性半导体激光器电源。设计了适合电源使用的"n+1"冗余并联结构和大电流恒流臂结构;分析了一个场效应管失效、一个电阻R失效以及控制网络失效导致恒流臂失效的情况下,电源的输出特性;最后测试电源样机,分别短路一个场效应管,开路一个电阻,短路所有场效应管,测量恒流臂的电流大小,实验结果和设计相符合。基于"n+1"冗余并联结构的半导体激光器电源,可靠性高,只需采用廉价的场效应管,就可实现大电流恒流输出,成本大为降低,具有较广泛应用前景。     

Improved multi-objective artificial bee colony algorithm for optimal power flow problem

The artificial bee colony（ABC） algorithm is improved to construct a hybrid multi-objective ABC algorithm, called HMOABC, for resolving optimal power flow（OPF） problem by simultaneously optimizing three conflicting objectives of OPF, instead of transforming multi-objective functions into a single objective function. The main idea of HMOABC is to extend original ABC algorithm to multi-objective and cooperative mode by combining the Pareto dominance and divide-and-conquer approach. HMOABC is then used in the 30-bus IEEE test system for solving the OPF problem considering the cost, loss, and emission impacts. The simulation results show that the HMOABC is superior to other algorithms in terms of optimization accuracy and computation robustness.     

Influence of lateral initial pressure on axisymmetric wave propagation in hollow cylinder based on first powerhypo-elastic model简

Influence of identical applied initial pressures on the radial surfaces of a hollow cylinder which is compose of materials with first power hypo-elastic constitutive model was investigated.The basic equations of the problem were built up based on the framework of piecewise homogeneous body model with the use of three-dimensional linearized theory of elastic waves in initially stressed bodies（TLTEWISB）.With the method proposed previously,this problem was then solved numerically.Moreover,the dispersion group velocity of the lowest order mode with different initial pressures was also studied.It can be concluded that the initial pressure and the geometry parameters will induce considerable changes of different degrees in dispersive relation between phase velocity and wave number in opposite trend（positive in initial pressure and negative in thickness）.     

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine（S-VAWT） appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.     

Two new methods for power flow tracing using bus power balance equations

Two new methods were presented for power flow tracing（PFT）.These two methods were compared and the results were discussed in detail.Both methods use the active and reactive power balance equations at each bus in order to solve the tracing problem.The first method considers the proportional sharing assumption while the second one uses the circuit laws to find the relationship between power inflows and outflows through each line,generator and load connected to each bus of the network.Both methods are able to handle loop flow and loss issues in tracing problem.A formulation is also proposed to find the share of each unit in provision of each load.These methods are applied to find the producer and consumer＇s shares on the cost of transmission for each line in different case studies.As the results of these studies show,both methods can effectively solve the PFT problem.     

Preparation and characterization of Andalusite ceramic used for solar thermal power generation

High-temperature thermal storage material is one of the critical materials of solar thermal power generation system. Andalusite, kaolin, talc, γ-Al 2 O 3 and partially stabilized zirconia were used as the raw materials, and in-situ synthesis of cordierite was adopted to fabricate thermal storage material for solar thermal power generation via pressureless sintering. The phase compositions, microstructures and thermal shock resistances of the sintered samples were analyzed by XRD, SEM and EDS, and the corresponding mechanical properties were measured. The results show that the major phases of the samples are mullite and zirconium silicate, and the pores distribute uniformly. After being sintered at 1 460 ℃, A4 sample exhibits a better mechanical performance and thermal shock resistance, its loss rate of bending strength after 30 cycles thermal shock is 3.04%, the bulk density and bending strength are 2.86 g·cm-3 and 139.66 MPa, respectively. The better thermal shock resistance of the sample is closely related to the effect of zirconium silicate, such as its uniform distribution, nested growth with mullite, low thermal expansion coeffi cient, high thermal conductivity, etc. This ceramic can be widely used as one of potential thermal storage materials of solar thermal power generation system.