基于拥挤距离的多目标粒子群优化算法在漳河水库优化调度中的应用

针对传统多目标优化算法的不足,提出了基于拥挤距离的多目标粒子群优化算法(MOPSO CD),该算法用拥挤距离来维持精英策略和选取全局极值,同时引入动态非均匀变异算子,用以维持粒子多样性、减缓算法收敛速度、避免早熟收敛。以漳河水库为例,建立了以灌溉缺水量最小和发电量最大为目标函数的两目标优化调度模型,将MOPSO CD应用于模型的求解中,得到了足够多且较均匀的非劣（Pareto）解前端。     

基于寿命的电缆群载流能力优化研究

采用周期性条件计算得到的载流量能提高电缆的载流能力,在周期性载流量的基础上提出一种周期性寿命最大允许电流模型。鉴于电缆周期性寿命最大允许电流与电缆寿命之间互相影响,采用多目标粒子群算法,考虑电缆的互为热源效应,以电缆群的平均寿命和平均周期性寿命最大允许电流为目标函数,在改进周期性载流量设置方法的基础上提出周期性寿命最大允许电流设置方法,然后对电缆群中每条回路的周期性寿命最大允许电流和寿命进行优化,从而找到电缆群的优化运行方式,并深入研究了电热联合老化对两个目标函数的影响。     

基于效益模型的锅炉燃烧综合性能多目标优化

建立了锅炉燃烧综合性能多目标优化问题的数学模型,给出了基于改进的多目标粒子群优化算法的解决方案,提出了兼顾经济、环保和节能的锅炉燃烧优化综合评价目标,并对由锅炉效率、NOx排放质量浓度和辅机电耗构成的三目标寻优问题进行优化,提出了一种基于效益模型的多目标优化结果判别方法.结果表明:多目标粒子群优化算法可有效处理多目标之间的寻优比较工作,利用其多点并行搜索特性能够同时得到含有多组非劣解的Pareto最优解集,通过判别方法可以快速确定最优燃烧调整方式.     

罚函数改进粒子群算法的风光储系统优化配置

考虑风光储系统中风光资源、储能和负载之间复杂的匹配关系,建立以年度平均发电成本(AAGC)为优化目标,以全年负载缺电率(LPSP)为约束条件的优化模型。采用改进的粒子群算法(IPSO),并加入罚函数将非线性约束条件转化为一系列无约束问题。在考虑各组件数量作为决策变量的基础上,增加风力机塔架高度以及光伏板倾角用以提高优化过程的全面性。通过对算例的计算,对比分析各组件最优配置结果和多目标遗传算法结果,证明算法的有效性和优越性。     

基于改进粒子群算法的多目标无功优化

提出了一种基于粒子群算法的多目标优化方法,该算法采用Pareto支配关系来更新粒子的个体最优和全局最优值,用存储池保存搜索过程中发现的非支配解;采用聚类算法裁剪非支配解,以保持解的分散性;采用动态惯性权重来平衡粒子的局部和全局搜索能力,并将该算法应用于IEEE14节点系统的多目标无功优化。     

多目标粒子群优化算法在光伏MPPT中的应用

为提高光伏电池的利用率,需要进行光伏阵列的最大功率点跟踪(MPPT),针对传统粒子群优化算法在多目标优化中的不足,提出了基于最小粒子角度的多目标粒子群优化算法,利用目标空间中不同粒子之间的角度进行粒子全局极值更新,通过比较粒子的浓度值给出粒子群及粒子个体极值更新方法,并在Matlab/Simulink下进行了建模与仿真。仿真结果显示,该算法在外界环境变化时能快速准确地跟踪太阳能电池的最大功率点,并能保证系统的稳定性。     

考虑机组组合问题的机组检修计划优化新模型

以经济费用最小为目标函数,建立了发电机组检修计划优化问题（UMS）新模型。由于生产费用在经济费用中占有的比例最大,因此在计算新模型的生产费用时考虑了发电机组组合优化问题（UC）。鉴于考虑UC问题的UMS问题为双层优化问题,其中UMS问题为上层优化问题,UC问题为下层优化问题,提出了一种改进离散粒子群算法（MDPSO）,并将其用于搜索UMS问题的最优解向量,即解决上层优化问题;而由于拉格朗日松弛法在解决UC问题上具有计算速度快、结果精度高等优点,将其用于解决下层优化问题。利用该新模型和MDPSO算法对IEEE-RTS系统的机组的年检修计划进行优化,并与离散粒子群算法（DPSO）比较,结果表明DPSO算法在解决UMS问题上具有精度高、收敛速度快等优点。     

基于粒子群优化BP神经网络的风电机组齿轮箱故障诊断方法

提出了一种基于粒子群优化BP神经网络风电机组齿轮箱故障诊断方法。粒子群算法不需要计算梯度,可以兼顾全局寻优和局部寻优。利用粒子群算法对BP网络权值和偏置进行优化,减少了BP神经网络算法陷入局部最优解的风险,提高了神经网络的训练效率,加快了网络的收敛速度。考虑风电齿轮箱振动信号的不确定性、非平稳性和复杂性,提取功率谱熵、小波熵、峭度、偏度、关联维数和盒维数作为故障特征。经测试,算法诊断结果正确,表明了PSO优化BP神经网络用于风电机组齿轮箱故障诊断的有效性和实用性。     

考虑灵活性供需匹配的孤岛微网优化调度策略

为使孤岛微网能更大程度地实现源侧发电功率与荷侧用电需求之间的匹配程度,以灵活性理论为依据,提出考虑灵活性供需匹配的优化调度模型。以最大化经济效益和最大化灵活性供需匹配程度为目标,利用多目标粒子群优化算法得到该优化问题的Pareto解集,并从中选取更符合实际需求的解。算例仿真结果表明,所提优化调度策略能有效提升系统应对可再生能源发电机组出力的波动性与随机性的能力,提高经济效益。     

基于相似搜索与多开端重组的配电网两时间尺度无功协调控制

规模化的分布式电源接入配电网后造成了电压高间歇性波动,影响了无功补偿设备的调节效果。提出基于相似搜索与多开端重组的多目标无功优化算法,考虑了非平滑补偿设备的日投切次数限制,加入变化的次数成本约束,调节尺度为1 h;DG和SVG的实时平滑调节设备,调节尺度为5 min,进行超短期预测反馈调节,优化目标为电压偏差、网损和调控成本综合最优。求解算法采用改进的多目标粒子群算法,运用相似搜索技术,调用适用性最高的历史无功方案作为方案粒子加快算法的初期收敛速度;引用Pareto熵协调多目标间的适应度,同时依托Pareto解集存优能力,在算法收敛后期设计了多开端重组方法,进一步提高优化效果。经实际算例验证了该方法的有效性。     

Constructal Optimization of Louver Fin Channels Subjected to Heat Transfer Rate Maximization and Pressure Loss Minimization

To obtain better fluid mixing and higher heat transfer rate in the low Reynolds number regime, various types of fins have been employed for electronic cooling applications. However, previous works showed that there are no remarkable differences in the thermal performance of a straight-plate and a channel with louvered-fins when the Reynolds number is low or moderate. In this paper, the Constructal law is applied to optimize the geometry of a channel with louvered-fins, where the objective is to maximize the total heat transfer rate and minimize the pressure loss. The selected domain has three degrees of freedom; the louver angle ratio, the louver pitch ratio, and the inlet louver length to outlet louver length ratio. The results showed that the effect of louver on the louver pitch ratio and the inlet louver length to outlet louver length ratio. There is a minimum value for the louver pitch ratio and below this value the vortices upstream of the turnaround louver block the distance between louvers and so decreases the flow efficiency. A comparison between results and previous experimental studies indicated that the channel optimized by constructal law is considerably superior compared to the standard channel in low Reynolds number regime.     

Multi-objective optimization of a hybrid distributed energy system using NSGA-II algorithm

In this paper, a multi-objective optimization model is established for the investment plan and operation management of a hybrid distributed energy system. Considering both economic and environmental benefits, the overall annual cost and emissions of CO₂ equivalents are selected as the objective functions to be minimized. In addition, relevant constraints are included to guarantee that the optimized system is reliable to satisfy the energy demands. To solve the optimization model, the nondominated sorting generic algorithm II (NSGA-II) is employed to derive a set of non-dominated Pareto solutions. The diversity of Pareto solutions is conserved by a crowding distance operator, and the best compromised Pareto solution is determined based on the fuzzy set theory. As an illustrative example, a hotel building is selected for study to verify the effectiveness of the optimization model and the solving algorithm. The results obtained from the numerical study indicate that the NSGA-II results in more diversified Pareto solutions and the fuzzy set theory picks out a better combination of device capacities with reasonable operating strategies.     

Free Convective Flow of Electrically Conducting and Viscous Immiscible Fluid Flow in a Vertical Channel in the Presence of First‐Order Chemical Reaction

In this paper, the effects of chemical reaction on free convective flow of electrically conducting and viscous incompressible immiscible fluids are analyzed. The coupled nonlinear equations governing the heat and mass transfer are solved analytically and numerically with appropriate boundary conditions for each fluid and the solutions have been matched at the interface. The analytical solutions are solved by using regular perturbation method valid for small values of perturbation parameter and numerically by using finite difference method. The numerical results for various values of thermal Grashof number, mass Grashof number, Hartman number, viscosity ratio, width ratio, conductivity ratio, and chemical reaction parameter have been presented graphically in the presence and in the absence of electric field load parameter. In addition, the closed form expression for volumetric flow rate, Nusselt number, species concentration, and total heat rate added to the flow is also analyzed. The solutions obtained by finite difference method and perturbation method agree very well to the order of 10^?4 for small values of perturbation parameter.     

Experimental and theoretical studies of recyclic flat-plate solar water heaters equipped with rectangle conduits

A recycle operation design using a flat-plate solar water heater with rectangle flow conduits was theoretically and experimentally investigated. Devices with differing flow-conduit geometries (i.e. aspect ratio) and external recycle were designed to create a solar heater with low heat-transfer resistance between the absorber and working fluid to increase the convective heat-transfer coefficient. Considerable solar water heater collector efficiency improvement has been obtained employing rectangle flow conduits and a recycle operation, instead of recycle solar collector constructed with circular pipes operated at the same total mass flow rate. Under a fixed absorber area and distance between the flow conduits, the collector efficiency increases with increasing flow conduit aspect ratio, total mass flow rate and recycle ratio but with decreasing inlet water temperature. The incident solar radiation, mass flow rate, recycle ratio and flow conduit aspect ratio influences on the collector efficiency and energy consumption are also discussed.     

Optimal hybrid PV/WT/FC sizing and distribution system reconfiguration using multi-objective artificial bee colony (MOABC) algorithm

In this paper, a novel multi-objective artificial bee colony algorithm is presented to solve the distribution system reconfiguration and hybrid (photo voltaic/wind turbine/fuel cell) energy system sizing. The purposes of the multi-objective optimization problem include the total power loss, the total electrical energy cost, and the total emission produced by hybrid energy system and the grid minimization, and the voltage stability index (VSI) of distribution system maximization. In the proposed algorithm, an external archive of non-dominated solutions is kept which is updated in each iteration. In addition, for preserving the diversity in the archive of Pareto solutions, the crowding distance operator is used. This algorithm is tested on 33 bus distribution systems and obtained non-dominated solutions are compared with the well-known NSGA-II and MOPSO methods. The solutions obtained by the MOABC algorithm have a good quality and a better diversity of the Pareto front compared with those of NSGA-II and MOPSO methods.     

The flow of a combustible gas in a horizontal pipe

The flow of high temperature combustible gas in a horizontal pipe is studied as a model for a biomass moving bed gasifier. The general problem is a fully developed flow in a pipe in the presence of free convection heat transfer. When the flow Reynolds number is low, asymptotic solutions are developed. Several limiting solutions are developed for the basic nonlinear approximation. The higher approximations are linear and are tackled analytically and by a finite difference scheme employing central differences. The results are discussed quantitatively.     

Experimental and numerical research on high pumping performance mechanism of lobed exhauster-ejector mixer

The lobed nozzle exhauster-ejector mixer has a lot of potential applications in industry. The experimental setup is established to explore its high pumping performance mechanism. Experimental results show that the pumping performance is dominantly dependent on the primary flowing fluid “attachment” on the inner wall of the mixer. If the primary flowing fluid attaches the inner wall of the mixer in the exit section, the pumping ratio of the entrained secondary mass flow rate to the primary mass flow rate is definitely high. In order to find the high pumping performance mechanism from flow field, the N–S equations are solved. The numerical results show that the flow field to give high or the highest pumping ratio is that there is a distinct thin layer (tear layer) of the secondary flowing fluid with less velocity on the inner wall of the mixer. The distinct thin layer much decreases the friction loss between the primary high-speed flow and the solid wall. The necessary conditions for establishing the distinct thin layer are that the cross-area ratio is not too high or too low and the expand angle of the conical mixer is slightly less than the initial diffusion angle of the primary eject flow. According to the experimental and numerical results, the conical mixer with the cross-area ratio of 2.5 and the expand angle of 14.4° gives the highest pumping ratio of 0.528. The highest pumping ratio 0.598 for cylindrical mixers is experimentally in the case of the cross-area ratio of 3.8. The reason for the highest pumping ratio difference between the conical mixer and the cylindrical mixer is that in the cylindrical mixer the primary flowing fluid properly attaches the inner wall of the mixer in the outlet section and there is a larger space with negative pressure downstream of the lobed nozzle for entraining the secondary flowing fluid.     

Constructal entransy dissipation rate minimization of a disc

Disc cooling problem is optimized by taking entransy dissipation rate minimization as optimization objective. The non-dimensional mean temperature difference of the disc cooling model with radial high conducting fins inserted is deduced. The effects of the fin geometry, the fin aspect ratio, the ratio between the high conductivity and low conductivity, the relative amount of high conductivity material and the number of high conducting fins on the entransy dissipation rate of disc cooling are analyzed. The optimization results show that the high conducting fin should be extended to the centre of circle as the heat transfer effect of the high conducting fins is improved, and there exists an optimal fin aspect ratio corresponding to minimum entransy dissipation rate for different high conducting effects of the fin, and the number of high conducting fins has a slight effect on the entransy dissipation rate. Comparison with those for maximum temperature difference minimization shows that the constructs based on entransy dissipation rate minimization are different from those based on maximum temperature difference minimization, but the optimal constructal shape changing potentials of the number of fins and the relative amount of high conductivity material are similar.     

The recycle effect on the collector efficiency improvement of double-pass sheet-and-tube solar water heaters with external recycle

The paper presents a theoretical prediction of the performance of a double-pass sheet-and-tube solar water heater with external recycle and comparison with that of a conventional type collector. Analytical results show that the recycle effect can effectively enhance the collector efficiency compared with that in a single-pass device with the same flow rate. The desirable effect of increasing convective transfer rate and the undesirable effect of reducing heat-transfer driving force are the two conflict effects produced by the recycle operation. It was found that the increment of convective transfer rate by increasing the recycle ratio could generally compensate for the decrement of the temperature difference, leading to improved performance, especially for low flow rate. Also, the collector efficiency increases with increasing collector aspect ratio (i.e. either increasing the tube length or decreasing the number of tube pairs) for a specified collector area and the distance between tubes.