并网光伏系统性能检测初探

光伏发电系统的性能以及输出的电能质量是决定太阳能光伏发电系统能否规模化应用的关键因素。然而,国内目前还没有一套统一、有效、合理的对光伏发电系统进行评估和检测的标准及与之对应的技术方案。这已成为摆在每个光伏认证和检测工作者面前急需解决的问     

Multi-objective system reliability-based optimization method for design of a fully parametric concept car body

This article investigates multi-objective optimization under reliability constraints with applications in vehicle structural design. To improve computational efficiency, an improved multi-objective system reliability-based design optimization (MOSRBDO) method is developed, and used to explore the lightweight and high-performance design of a concept car body under uncertainty. A parametric model knowledge base is established, followed by the construction of a fully parametric concept car body of a multi-purpose vehicle (FPCCB-MPV) based on the knowledge base. The structural shape, gauge and topology optimization are then designed on the basis of FPCCB-MPV. The numerical implementation of MOSRBDO employs the double-loop method with design optimization in the outer loop and system reliability analysis in the inner loop. Multi-objective particle swarm optimization is used as the outer loop optimization solver. An improved multi-modal radial-based importance sampling (MRBIS) method is utilized as the system reliability solver for multi-constraint analysis in the inner loop. The accuracy and efficiency of the MRBIS method are demonstrated on three widely used test problems. In conclusion, MOSRBDO has been successfully applied for the design of a full parametric concept car body. The results show that the improved MOSRBDO method is more effective and efficient than the traditional MOSRBDO while achieving the same accuracy, and that the optimized body-in-white structure signifies a noticeable improvement from the baseline model.     

Models for the schedule optimization problem at a public transit terminal

This work deals with the proposal of some models for the schedule optimization problem for public transit networks. In particular, we consider the case of a transit terminal where passengers are supposed to split among different lines of a service, or even change mode of transportation in case of intermodal systems. Starting from a given schedule for the transit lines arriving at the terminal, the aim is to decide the optimal schedule for the output lines, in such a way to balance the operative costs of the service and the passenger waiting time at the transit terminal. We propose two different models for this problem, which present strong similarities with some well known combinatorial optimization models. Computational results are also presented, showing the suitability of the models to solve real case studies.     

Multi-objective optimization of stiffness and workspace for a parallel kinematic machine

This paper presents optimizations of a parallel kinematic manipulator used for a machine tool in terms of its workspace and stiffness. The system stiffness and workspace of the parallel manipulator are conducted in the paper. In order to locate the maximum system stiffness and workspace, single and multi-objective optimizations are performed in terms of rotation angles in x and y axes and translation displacement in z axis with genetic algorithms. By optimizing the design variables including geometric dimensions of the manipulator, the system stiffness and workspace of the proposed parallel kinematic manipulator has been greatly improved.     

Multi-objective optimization of water consumption for a methanol synthesis process

Clean Technologies and Environmental Policy - Methanol is an important product in chemical industries, having many applications: solvent, fuel and mainly being a feedstock for a large number of...     

Multi-objective robust optimization design of a front-end underframe structure for a high-speed train

A multi-objective robust design optimization of a front-end underframe structure for application in high-speed trains is proposed and the structural parameter uncertainty is considered. A finite element model of the structure is developed and verified by dynamic impact experiments. The sensitivity analysis demonstrates that the thicknesses of the centre sill have significant influences on structural crushing behaviours. The specific energy absorption and the initial peak crushing force (F_p) are taken as optimization objectives. Compared with the baseline structure, the 6-sigma robust design shows that the F_p and the structural mass are reduced by 54.86% and 13.06%, respectively, and the robust optimum is more reliable. The 6-sigma robust optimal solution has an efficient energy-absorbing capacity while satisfying the design constraint. Thus, 6-sigma robust optimization can be applied for high-speed trains.     

Multi-objective robust design optimization of fatigue life for a welded box girder

To reduce the scatter of fatigue life for welded structures, a robust optimization method is presented in this study based on a dual surrogate modelling and multi-objective particle swam optimization algorithm. Considering the perturbations of material parameters and environment variables, the mean and standard deviation of fatigue life are fitted using dual surrogate modelling and selected as the objective function to be minimized. As an example, a welded box girder is presented to reduce the standard deviation of fatigue life. A set of non-dominated solutions is produced through a multi-objective particle swam optimization algorithm. A cognitive approach is used to select the optimum solution from the Pareto sets. As a comparative study, traditional single objective optimizations are also presented in this study. The results reduced the standard deviation of the fatigue life by about 16.5%, which indicated that the procedure improved the robustness of the fatigue life.     

公共建筑空调系统节能设计的若干思考

本文结合工程实践经验,详细探讨了影响公共建筑空调系统节能设计主要几个问题,包括空调冷热负荷设计计算重要参数选取,空调冷热源选取模式,以及空调输配水系统等,以供专业人员在工程设计中参考.     

Development of a flickermeter for grid-connected wind turbines using a DSP-based prototyping system

The measurement of one of the power-quality problems (flicker), which may arise due to the presence of wind-turbine generators, is presented. This paper focuses on the design of a complete fully digital flickermeter relying on an in-house-developed measurement system, which features a data-acquisition system, using a C6711 DSP-based starter kit (DSK) and a field programmable gate array (FPGA). To study flicker produced during the wind turbine's continuous operation, special attention is given to the simulation of the voltage fluctuations on a fictitious grid.     

Multi-objective design optimization of reconfigurable machine tools: a modified fuzzy-Chebyshev programming approach

A reconfigurable manufacturing system (RMS) is designed for rapid adjustment of functionalities in response to market changes. A RMS consists of a number of reconfigurable machine tools (RMTs) for processing different jobs using different processing modules. The potential benefits of a RMS may not be materialized if not properly designed. This paper focuses on RMT design optimization considering three important yet conflicting factors: configurability, cost and process accuracy. The problem is formulated as a multi-objective model. A mechanism is developed to generate and evaluate alternative designs. A modified fuzzy-Chebyshev programming (MFCP) method is proposed to achieve a preferred compromise of the design objectives. Unlike the original fuzzy-Chebyshev programming (FCP) method which imposes an identical satisfaction level for all objectives regardless of their relative importance, the MFCP respects their priority order. This method also features an adaptive satisfaction-level-dependent process to dynamically adjust objective weights in the search process. A particle swarm optimization algorithm (PSOA) is developed to provide quick solutions. The application of the proposed approach is demonstrated using a reconfigurable boring machine. Our computational results have shown that the combined MFCP and PSOA algorithm is efficient and robust. The advantages of the MFCP over the original FCP are also illustrated based on the results.     

Multi-objective optimization of suspension parameters for rail vehicles based on a virtual prototype surrogate model

This research is intended to develop a suspension parameter optimization approach based on a virtual prototype surrogate model of rail vehicles considering the coupling effects of suspension parameters. In order to analyze the effects on the dynamic indexes, which were affected by the suspension parameters, a virtual prototype model of a rail vehicle was established. The indexes of lateral ride quality and motion stability were obtained under different combinations of suspension parameters by design of experiment and simulation of virtual prototype. For constructing objective function of multi-objective optimization model for suspension parameters, the suspension parameters that have significant effects on ride quality and motion stability simultaneously were taken as the design variables, and thereafter Kriging models of lateral ride quality index, derailment coefficient, and reduction ratio of wheel load were obtained. On this basis, the multi-objective optimization model of suspension parameters was established, in which the objective function was combined with the three Kriging models. Then, the Pareto optimal solution set and concrete value of suspension parameters were sought using the NSGA-II algorithm. The dynamic simulation results indicated that both ride quality and motion stability of the rail vehicle had been improved after the multi-objective optimization of suspension parameters.     

Magnetic charged system search: a new meta-heuristic algorithm for optimization

An improved version of the charged system search (CSS) algorithm is introduced which is called magnetic charged system search (MCSS). In the new algorithm, magnetic forces are considered in addition to electrical forces, using the Biot–Savart law. Each charged particle (CP), as a search agent, exerts magnetic forces on other CPs based on the variation of its objective function value during its last movement and its distance between other CPs. This additional force provides useful information for the optimization process and enhances the performance of the CSS algorithm. The efficiency of the MCSS is examined by application of this algorithm to well-known mathematical benchmarks and three well-studied engineering design problems. The results are compared to those of the CSS, and the improvements are highlighted.     

Joint optimization of maintenance and inventory policies for a simple system

We examine age replacement and ordering decisions for a system with only one component subject to random failure and with room for only one spare in stock. The system incurs costs for replacement, shortage, holding, and breakage; the lead time for receipt of an ordered spare is constant. We consider the solvability and desirability of jointly optimizing these two traditionally separate decisions. We show that the problem has some convexity properties that make it amenable to minimization. For our data set, we find that using separate optimization gives an average loss of 3% relative to the joint minimum; about a tenth of die time the difference was more than 10%, but in general this loss can vary from zero to arbitrarily large.     

Ant system for reliability optimization of a series system with multiple-choice and budget constraints

Many researchers have shown that insect colonies behavior can be seen as a natural model of collective problem solving. The analogy between the way ants look for food and combinatorial optimization problems has given rise to a new computational paradigm, which is called ant system. This paper presents an application of ant system in a reliability optimization problem for a series system with multiple-choice constraints incorporated at each subsystem, to maximize the system reliability subject to the system budget. The problem is formulated as a nonlinear binary integer programming problem and characterized as an NP-hard problem. This problem is solved by developing and demonstrating a problem-specific ant system algorithm. In this algorithm, solutions of the reliability optimization problem are repeatedly constructed by considering the trace factor and the desirability factor. A local search is used to improve the quality of the solutions obtained by each ant. A penalty factor is introduced to deal with the budget constraint. Simulations have shown that the proposed ant system is efficient with respect to the quality of solutions and the computing time.     

舰载武器系统研制方案多目标生成与评价方法

舰载武器系统研制方案的生成、评价与优选问题是武器装备研制论证中的重要内容．在分析目前舰载武器系统研制方案论证方法的基础上，构建了舰载武器系统多目标优化模型，提出了舰载武器系统研制方案的多目标生成方法，并建立了不完全偏好信息的舰载武器系统研制方案的多目标评价与优选模型．实例分析说明，该模型与方法是有效的，可为武器装备研制论证问题提供辅助决策方法和智力支持．     

Thermoeconomic optimization of a two stage combined refrigeration system: a finite-time approach

A finite-time thermoeconomic performance analysis based on a new kind of optimization criterion has been carried out for a two-stage endoreversible combined refrigeration cycle model. The optimal performances and design parameters that maximize the objective function (cooling load per total cost) are investigated. In this context, the optimal temperatures of the working fluids, the optimum performance coefficient, the optimum specific cooling load and the optimal distribution of the heat exchanger areas are determined in terms of technical and economical parameters. The effects of the economical parameter that characterizes the investment and energy consumption costs on the general and the optimal performances have been discussed.     

An expert system for finding fragility curves of building structural systems at the preliminary design stage

This research developed an expert system for determining seismic fragility curves of structural systems in a nuclear power plant or conventional building at the preliminary design stage. The resulting system simulates the performance of human experts in identifying the potential failure modes and their likelihood for a structure of interest. Induction technique is used for knowledge acquisition. The characteristics of structural systems are described by their attributes and their values.     

Experimental and dynamic system simulation and optimization of a centrifugal pump-coupling-engine system. Part 2: System design

A comprehensive theoretical non-linear torsional dynamic model of a pump-coupling-engine assembly has been constructed, with some of the system characteristics evaluated through the finite element method. Coupling elements have non-constant stiffness, which makes the dynamic system non-linear. The resulting model provided information on the torsional vibration response of the system and therefore allowed analysis of the effect of different designs on the torsional system dynamics. Model outputs have been compared to experimental test rig results where system rotational inertia and four different couplings have been studied. The main aim of the work was to improve system design in order to guarantee reliable operation. The model facilitated a dynamic characterization of the system and has been used as predictive tool for subsequent design.     

Development of a MINLP model for the optimization of a large industrial water system

This paper presents the design of a large water system within the production and packaging areas of a brewery. In order to accomplish the task, mathematical models were developed based on a Mixed Integer Nonlinear Programming (MINLP) formulation from the open literature. These models enable the investigation of several integration options: a) direct water re-use between batch and semi-continuous consumers operating within the same time interval and b) regeneration re-use options, by designing and scheduling an on-site wastewater treatment system. A multilevel strategy was applied for this large-scale industrial problem, which firstly decomposes design problem into several smaller integration problems concerning water consumers within each section of the brewery. At the following level, water re-use and regeneration re-use opportunities between the brewhouse and the packaging areas were explored for each working day. Finally, the design of an integrated water system was performed over the entire working week by fixing identified intra-daily matches between sections. An optimum water integration scheme is proposed based on the results obtained.