Application of Dynamic Programming Method in Optimization of Water Distribution Pipe Network

With a water-supply network by dynamic programming. The minimal as an example, the network was optimized annual discounted costs were taken as an objective function and node pressure etc. as constraint conditions. The alternative pipe diameters were optimized as per enumeration method and the group allowing objective function with the least values would be the optimized one. It is proved the optimized pipe network reduced by 11.49% in terms of cost and the optimized ben- efits proved much significant.

Conjunctive Use of Engineering and Optimization in Water Distribution System Design

Water Distribution Systems (WDSs) design and operation are usually done on a case-by-case basis. Numerous models have been proposed in the literature to solve specific problems in this field. The implementation of these models to any real-world WDS optimization problem is left to the discretion of designers who lack the necessary tools that will guide them in the decision-making process for a given WDS design project. Practitioners are not always very familiar with optimization applied to water network design. This results in a quasi-exclusive use of engineering judgment when dealing with this issue. In order to support a decision process in this field, the present article suggests a step-by-step approach to solve the multi-objective design problem by using both engineering and optimization. A genetic algorithm is proposed as the optimization tool and the targeted objectives are: 1) to minimize the total cost (capital and operation), 2) to minimize the residence time of the water within the system and 3) to maximize a network reliability metric. The results of the case study show that preliminary analysis can significantly reduce decision variables and computational burden. Therefore, the approach will help network design practitioners to reduce optimization problems to a more manageable size.

STUDY ON OPTIMAL CONTROL OF MUNICIPAL WATER DISTRIBUTION NETWORK

A systematic investigation is made on the problems which are related to the optimal control of the municipal water distribution network.A mathematical model of forecasting the water short term demand is proposed using the time series trigonometric function analysis method;the service discharge based macroscopic model of network performance is established using the network structuring method;a relatively satisfactory mathematical model for the optimal control of water distribution network is put forward in view of security and economy,and solved by the constrained mixed discrete variable complex arithmetic.The model is applied in many examples and the results are satisfactory.

Multi-objective Optimisation Design of Water Distribution Systems:Comparison of Two Evolutionary Algorithms

In order to compare two advanced multi-objective evolutionary algorithms,a multi-objective water distribution problem is formulated in this paper.The multi-objective optimization has received more attention in the water distribution system design.On the one hand the cost of water distribution system including capital,operational,and maintenance cost is mostly concerned issue by the utilities all the time;on the other hand improving the performance of water distribution systems is of equivalent importance,which is often conflicting with the previous goal.Many performance metrics of water networks are developed in recent years,including total or maximum pressure deficit,resilience,inequity,probabilistic robustness,and risk measure.In this paper,a new resilience metric based on the energy analysis of water distribution systems is proposed.Two optimization objectives are comprised of capital cost and the new resilience index.A heuristic algorithm,speedconstrained multi-objective particle swarm optimization( SMPSO) extended on the basis of the multi-objective particle swarm algorithm,is introduced to compare with another state-of-the-art heuristic algorithm,NSGA-II.The solutions are evaluated by two metrics,namely spread and hypervolume.To illustrate the capability of SMPSO to efficiently identify good designs,two benchmark problems( two-loop network and Hanoi network) are employed.From several aspects the results demonstrate that SMPSO is a competitive and potential tool to tackle with the optimization problem of complex systems.

Optimal operation of water distribution networks under local pipe failures

The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic model for a network under a local pipe failure was established by the statistical regression. After the operation objectives under a local pipe failure were determined, the optimal operation model was developed and solved by the genetic algorithm. The program was developed and examined by a city distribution network. The optimal operation alternative shows that the electricity cost is saved approximately 11%, the income of the water corporation is increased approximately 5%, and the pressure in the water distribution network is distributed evenly to ensure the network safe operation. Therefore, the proposed method for optimal operation under local pipe failure is feasible and cost-effective.

Distributed versus Lumped Optimization of Cropping Pattern and Water Resources Utilization

Several whole-farm agro-economic optimization models have been developed to deal with lumped planning issues in the agriculture sector. However, these models cannot be used to devise appropriate management strategies at land parcel level, because of the differences between farm characteristics, and the increased complexity of the hydrological processes. Based on Spatial Farm Database (SFD) which is consisted of a number of farm-level spatial data, including location, paddock properties, owner specifications and budgets, it is possible to provide the farm manager with some suggestions regarding the optimal choice of crops and the area to be allocated for each one. To this end, genetic algorithm is used in order to cope with model nonlinearity and a large number of decision variables. In order to test the proposed model, the Mobarakabad district is modeled with 126 agriculture fields, and the optimization model is run for this area. Results showed that the optimization procedure can find more realistic farm-level optimal solutions due to its advantage in adequate modeling of field characteristics, common groundwater resources, and the associated constraints. The results of lumped optimizations could also be used as benchmarks for the purposes of comparison and interpretation.

Hydraulic Reliability Assessment and Optimal Rehabilitation/Upgrading Schedule for Water Distribution Systems

This paper develops an innovative approach to optimize a long-term rehabilitation and upgrading schedule (RUS) for a water distribution system with considering both hydraulic failure and mechanical performance failure circumstances. The proposed approach assesses hydraulic reliability dynamically and then optimizes the long-term RUS in sequence for a water distribution system. The uncertain hydraulic parameters are treated as random numbers in a stochastic hydraulic reliability assessment. The methodologies used for optimization in a stochastic environment are: Monte Carlo Simulation, EPANET Simulation, Genetic Algorithms, Shamir and Howard’s Exponential Model, Threshold Break Rate Model and Two-Stage Optimization Model. The proposed approach is conducted on a simulation model of water distribution network in a computer by two universal codes, namely the hydraulic reliability code and the optimal RUS code. The applicability of this approach is verified in an example of a benchmark water distribution network.

Game Theory Applications in a Water Distribution Problem

A water distribution problem in the Mexican Valley is modeled first as a three-person noncooperative game. Each player has a five-dimensional strategy vector, the strategy sets are defined by 15 linear constraints, and the three payoff functions are also linear. A nonlinear optimization problem is first formulated to obtain the Nash equilibrium based on the Kuhn-Tucker conditions, and then, duality theorem is used to develop a computational procedure. The problem can also be considered as a conflict between the three players. The non-symmetric Nash bargaining solution is suggested to find the solution. Multiobjective programming is an alternative solution concept, when the water supply of the three players are the objectives, and the water authority is considered to be the decision maker. The optimal water distribution strategies are determined by using these solution concepts and methods.

Optimization of the Open Degree of Key Valves Based on Relative Entropy and Pipeline Leakage

Based on information entropy theory, the definition of relative entropy, and the relative entropy minimum principle, this study establishes a multi-objective optimization model for a key valve opening of an urban water distribution network (WDN). Each node pressure is taken as the main research object to reduce pipeline leakage. Moreover, genetic algorithm is applied in the proposed model to solve the key valve opening of the actual WDN in a city in southern China. Using the proposed model, the relevant decision variables of a WDN can be optimized to provide a new manner of network dispatching. © 2017, Tianjin University and Springer-Verlag GmbH Germany.

基于代理指标的供水管网抗震改造优化

基于水力模型计算的管网供水量满足率(SSIQ)指标,是评估供水管网震后性能的常用指标。在供水管网抗震改造优化模型中,若采用SSIQ表示优化目标函数,优化求解需进行大量水力模型计算,计算耗时很长。为减小管网抗震改造优化模型的计算量,对节点流量韧性指标(FR)进行了改进,增加了管道破坏漏水能量损失的影响项,提出了一种管网能量指标(Energy Resilience, ER)表示震后管网性能;以ER指标作为SSIQ的代理指标,用于量化抗震改造优化模型的目标函数。仅通过管道地震失效概率、管网震前正常运行工况的水力参数计算ER指标,不必进行震后管网水力模型计算,以期提升优化模型计算效率。以供水管网震后性能最大化和改造费用最小化为目标,以管道抗震改造措施为优化变量,建立了管网抗震改造多目标优化模型,并比较了ER指标、FR指标以及两个拓扑代理指标的替代效果。案例管网应用结果表明,ER指标与SSIQ指标相关系数呈现强相关性,基于ER指标的优化方案与基于SSIQ指标的优化方案的差异小于3%,ER指标优化模型计算时间不足SSIQ指标优化模型计算时间的1%。

换热站并联水泵分布式优化控制

针对现有换热站并联水泵优化算法在集中式架构下控制适应性不足的问题,本文提出了一种改进的分布式并联水泵优化算法.首先,建立了并联水泵的分布式控制系统,并对该优化问题的数学模型进行描述,在目标函数中引入自适应非线性因子;然后,设计了改进的分布式果蝇优化算法,在该算法中每台水泵的控制器仅通过与邻居控制器交互信息即可完成并联水泵的优化;并且,在嗅觉搜索阶段,使用正弦余弦策略替代赋予个体距离与方向的随机策略;最后,以两个实际换热站中不同并联水泵系统为例对算法进行仿真验证,并基于仿真结果进行性能分析.结果表明,相较于传统算法,改进的分布式果蝇优化算法能得到更优的控制策略,有着收敛速度快、稳定性好和鲁棒性强的特点;并且该算法适用于不同系统的并联水泵优化问题,具有可扩展性.在实际工程验证中相较于集中式算法,该算法在总功率和计算时间上分别平均降低了5.47%和29.90%,因此,能够满足实际换热站中对并联水泵热负荷优化分配的需求.

Algorithms for seismic topology optimization of water distribution network

As an essential lifeline engineering system,water distribution network should provide enough water to maintain people's life after earthquake in addition to working under daily operation.However,the design of water distribution network usually ignores the influence of earthquake,resulting in water stoppage in large area during many recent strong earthquakes.This study introduced a seismic design approach of water distribution network,i.e.,topology optimization design.With network topology as the optimization goal and seismic reliability as the constraint,a topology optimization model for designing water distribution network under earthquake is established.Meanwhile,two element investment importance indexes,a pipeline investment importance index and a diameter investment importance index,are introduced to evaluate the importance of pipelines in water distribution network.Then,four combinational optimization algorithms,a genetic algorithm,a simulated annealing genetic algorithm,an ant colony algorithm and a particle swarm algorithm,are introduced to solve this optimization model.Moreover,these optimization algorithms are used to optimize a network with 19 nodes and 27 pipelines.The optimization results of these algorithms are compared with each other.

泵站-水库原水调水系统经济运行方式优化

为提高泵站-水库原水调水系统中泵站的运行效益,最大限度降低输水系统的运行成本.通过分析该类输水系统特性以及供水方式,基于遗传算法构建泵站机组流量分配模型,优化分配泵站运行流量.在此基础上,考虑泵站时间维度上的运行方式,结合亳州加压泵站的工程状况和区域分时电价,以单位提水费用最小为优化目标,构建经济运行模型.将该方法应用于亳州供水工程,结果表明模型效果显著,并对历史运行区间内周期输水量进行离散计算,拟合得出周期内单位提水费用最低工况,进而对拟合结果进行分析.结果表明:所构建经济运行模型具有较好的适用性,可降低工程运行费用,为工程优化调度提供指导;受到泵站运行效率和分时电价的影响,泵站单位提水费用随调水量增加先降低后升高.

RESEARCH ON MATHEMATICAL SIMULATION OF RESIDUAL CHLORINE DECAY AND OPTIMIZATION OF CHLORINATION ALLOCATION OF URBAN WATER DISTRIBUTION SYSTEM

The concentration of Residual Chlorine (RC) frequently violates the standard in situations of urban water distribution system with large water supply area and long time of distribution. If chlorine dosage increases within water treatment plant, although RC in distribution system could meet water quality standard, Disinfection By-Products (DBPs) such as hydrocarbon halide rises. In the paper, a mathematical model of chlorine allocation optimization was presented based on reaction kinetics mechanism and optimization theory to solve the problem. The model includes the objective function of minimizing annual operation cost and constraints of RC standard and rational chlorination station distribution, and solving by 0-1 Integer Programming (IP). The model had been applied to a real water distribution system. The simulation results of the model showed that adding chlorine in water distribution system remarkably improved water quality and reduced the operation cost by 49.3% per year less than chlorine dosed only in water treatment plant to meet RC standard. The results prove adding chlorine in water distribution system based on the model can bring both technological and economic advancement.

Convexification and Hierarchical Optimization Algorithm for Distribution of Water Supply Systems

This paper deals with the optimal distribution problem of large urban water supply systems in our country.The mathematical model of the problem is developed.It possesses the separable,but nonconvex structure.In order for primal-dual methods to be applicable to this type of largescale and nonconvex optimization problem,a method by means of which a nonconvex problem is convexified is studied based on the principle of the multiplier methods in the paper.The decomposition-coordination optimization algorithm is proposed based on the convexification method and the multiplier methods.The algorithm has been simulated in some real urban water supply systems,and the satisfactory results are obtained.

基于供水量的两级渠系优化配水模型

【目的】基于灌区实际供水量构建两级渠系优化配水模型,提供各用水单元的配水量、配水流量、配水时间。【方法】本文分2种情形构建模型,情形1:非充分灌溉,作物某生育时期内供水无法满足需水,模型首先通过水资源配置确定每个用水户的分配水量,再通过渠系优化配水模型确定每条渠道的配水流量和配水时间;情形2:充分灌溉,供水能够满足需水,根据配置系数确定各渠道配水的优先次序,再确定配水流量和配水时间。【结果】将模型运用到山东省簸箕李灌区,验证模型的适用性,结果表明本模型能够根据灌区的供水量提供水资源配置方案和渠系配水方案。供水充足时,模型根据配置系数确定配水次序;供水不足时,模型根据分配系数确定水资源分配量。情形1和情形2支渠的配水流量分别在流量上限的0.8倍与0.75倍以上,做到了大流量配水;2种情形的配水周期分别为10.90、17.84 d,缩短了灌溉周期。【结论】本文建立的模型能够依据供水量首先提供水资源分配方案或配置次序,再以此为基础,提供配水方案,即配水流量、配水开始时间、配水结束时间,从而指导灌区的配水工作。

新疆五家渠灌区渠系优化配水研究

通过建立多目标渠系优化配水模型,优化渠系配水过程,为新疆农业节水灌溉提供科学依据。以新疆五家渠灌区新东干渠作为研究对象,采用多目标粒子群优化算法以配水渠道的渗漏损失量最小,水流稳定为优化目标,建立多目标渠系优化配水模型,并与回溯搜索算法就配水时间和渗漏损失量进行比较。研究表明,多目标渠系优化配水模型能将配水时间从15 d缩短至约11 d,渠系配水量为71.58万m^(3),与回溯搜索算法相比,配水时间从14 d缩短至11 d,渗漏量减少了8.39万m^(3)。采用多目标粒子群优化算法对新疆五家渠灌区新东干渠进行配水过程优化,不但满足了优化目标,减少了渠系渗漏,缩短了配水时间,且比回溯算法更具有实用性。

基于智能算法的灌区渠系多目标优化配水模型研究及其系统开发

优化灌区渠系输配水技术是推动农业水资源高效利用的重要举措。针对新疆部分灌区渠系管理上沿用人工传递信息方法来决策配水方案,难以达到优化调配。以轮灌分组和配水流量为决策变量,建立了以渠道输水损失最小、轮灌组内配水时间差最小为目标的灌区支、斗渠优化配水模型,采用多目标粒子群算法进行求解;在深入研究渠系优化配水模型及其算法求解的基础上,采用Visual Studio Code、Matlab开发工具,开发灌区渠系水优化配置系统,并通过实例进行检验分析。结果表明:优化后的配水方案较该时段实际灌溉方案,渗漏损失总量由48.49万m^(3)减少至23.78万m^(3),配水时间由30 d缩短为14.6 d。所建立的渠系优化配水模型贴近渠系实际运行情况,可以实现集中高效配水;开发的渠系水优化配置系统界面友好、参数简洁,能方便快速地为灌区的配水优化编组提供决策依据。

水量调度对平原河网能量影响分析

平原河网水动力条件相对较差,水质问题较为突出,为改善平原河网地区水环境状况,选取江苏省无锡市滨湖河网2018年洪季和枯季19个断面水文水质监测数据,基于MIKE21滨湖河网水动力-水质模型及Python能量计算模型,探究能量耗散规律以及能量、水质间的关系,并确定最佳调水流量区间。结果表明:滨湖河网水质浓度与河流能量显著负相关;一定调水流量的增加使得河流总能量随之上升,能量到达阈值后,随调水流量的上升,河流总能量呈降低趋势;在能量目标层面上优选引调水方案,能有效协调引调水过程中存在的异质性因素,确定逐日最佳调水流量区间及河网总能量最佳区间,提供流量优化调控方案,保障平原河网水动力与水环境条件。

基于全过程输水损失的灌区渠系优化配水模型构建——以长岗灌区为例

为发挥灌区用水调度决策潜能,以黑龙江省长岗灌区为研究区,提出一种基于全过程输水损失的灌区渠系优化配水多目标模型,该模型充分考虑灌区骨干渠系内不同渠段、渠道之间的水量平衡和各级渠道的输水能力,兼顾渠系输水损失、配水及时性与公平性多目标的协同,优化决策配水流量与输水历时。此外,利用随机森林模型预测未来气候变化情境下灌区的供需水量,基于此,计算未来气候模式下的渠系输水损失并获得长岗灌区渠系优化配水方案。结果表明:同一生育阶段内上级渠道不同渠段的输配水损失水量占上级渠道输配水损失总量的比例差异性显著,任一生育阶段内上级渠道靠近渠首的第一个渠段的输配水损失水量占比最大(返青期、抽穗开花期和乳熟期均为20.71%、分蘖期为21.21%、拔节孕穗期为25.43%);通过渠系优化配水模型得到长岗灌区作物全生育期渠系输配水总量为230.51万m^(3),总配水历时为494.32 h,输水损失总量为8.66万m^(3),与灌区采用经验系数法计算的输配水损失水量相比,输水损失减少24.89%,显著提高输配水效率。该模型有助于提供科学、合理的渠系配水方案,为综合提升灌区水资源管理能力和精细化管理水平提供决策支持。