Online Fault Detection Configuration on Equipment Side of a Variable-Air-Volume Air Handling Unit

With the development of the technology of the Internet of Things,more and more operational data can be collected from air conditioning systems.Unfortunately,the most of existing air conditioning controllers mainly provide controlling functions more than storing,processing or computing the measured data.This study develops an online fault detection configuration on the equipment side of air conditioning systems to realize these functions.Modbus communication is served to collect real-time operational data.The calculating programs are embedded to identify whether the measured signals exceed their limits or not,and to detect if sensor reading is frozen and other faults in relation to the operational performance are generated or not.The online fault detection configuration is tested on an actual variable-air-volume(VAV)air handling unit(AHU).The results show that the time ratio of fault detection exceeds 95.00%,which means that the configuration exhibits an acceptable fault detection effect.

Simulation of Variable Air Volume System with Different Duct Layout

The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.

Impact of air pollution on urbanization:evidence at China’s city level

This paper investigates the effect and transmission mechanism of air pollution on urbanization based on data from China’s 107 cities during 2005–2018.In order to identify the impact of air pollution on China’s urbanization,we utilized night light data to represent the level of urbanization and used temperature inversion as an instrumental variable to mitigate endogeneity within the two-stage least squares framework.The results suggest that air pollution significantly slowed China’s urbanization process with economic growth acting as the transmission mechanism.The heterogeneity analyses revealed that air pollution had a greater negative impact on urbanization in northern regions than that in southern regions,and a greater negative impact in resource-oriented cities than that in non-resource-based cities.We also find that air pollution was to the detriment of urbanization in larger cities,which have more than 3 million residents,while it did not have a significant impact on Type II large cities,which have fewer than 3 million residents.

基于改进BSO算法的VAV空调系统GPC参数整定

针对变风量(variable air volume,VAV)空调系统具有大滞后、强耦合等控制难点,提出了一种基于改进天牛群优化(beetle swarm optimization,BSO)算法的VAV空调系统广义预测控制(generalized predictive control,GPC)参数整定方法。针对标准GPC整定算法只调节控制加权系数λ导致控制性能不佳的问题,首先,提出一种改进BSO算法,通过动态化选取权重参数与学习因子获得较佳的寻优性能。其次,提出一种基于改进BSO算法的新型GPC参数整定方法,可同时整定控制器的控制加权系数λ、控制时域Nu、预测时域Np及柔化系数α。最后,结合实际VAV空调系统,开展仿真与半实物实验。结果表明,采用改进BSO算法调优后GPC的控制效果得到显著提升,调节时间仅为7 s,超调量仅为0.28%。

Design of Control Scheme for Variable Air Volume Air- conditioning System

The air quantity of variable air volume system for the rooms and the total air quantity of the system changes with the change of room load. Combined with the system composition in the laboratory, the paper determines the control scheme of the variable air volume system, that is, indoor temperature-control, indoor positive pressure control, air distribution static pressure control, air-supply temperature control and new air volume control. The dotted lines with arrows mean the output signals from the control unit to actuator, and the solid lines with arrows represent the input signals from the actuator to the control unit.

VAV变风量空调系统施工技术

以某工程为例,对VAV变风量空调系统施工技术进行研究,通过采用BIM技术对风管的形状、构造及布置进行深化设计,优化了系统布置,降低了能耗;采用DDC数字控制的变风量空调系统,实现与计算机联网一体化智能控制,通过VAV末端,实施对空调房间的智能控制,消除了送风温度的变化对室内温度的影响,达到节能的目的。

智能VAV通风柜PID控制系统的设计

针对传统的通风柜不能对面风速进行精准控制、无法保证实验的安全性等问题,提出了一种智能通风柜控制系统的设计方案,采用变风量控制(VAV)的方法保持通风管道静压恒定,通过PID控制算法自动调节风阀角度,实现通风柜的面风速保持恒定的要求。讨论了通风控制系统的滤波算法,并对PID控制算法进行了数值仿真,最后将仿真数据应用于通风系统的调试中,取得平稳的运行效果。

DISPLACEMENT CONTROL AND KINETIC ANALYSIS OF A NOVEL VARIABLE DISPLACEMENT COMPRESSOR FOR AUTOMOTIVE AIR CONDITIONER

A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and instead of pneumatic valve the displacement is controlled by electronic control valve. In order to know the control mechanism well and get a good control effect, a mathematical model for the variable displacement mechanism is developed according to the geometrical and kinematical information of the compressor. Using the model, the effect of relevant parameters on variable displace control is estimated. It is helpful to make the optimum decision in the flow control of AAC. As the novel displacement control device, the structure and control rule of electronic control valve is introduced. It can get better effect than the conventional pneumatic valves. And by using this new electronic control device, the optimum systemic control of AAC is available.

Genetic Optimization Algorithm of PID Decoupling Control for VAV Air-Conditioning System

Variable-air-volume (VAV) air-conditioning system is a multi-variable system and has multi coupling control loops. While all of the control loops are working together, they interfere and influence each other. A multivariable decoupling PID controller is designed for VAV air-conditioning system. Diagonal matrix decoupling method is employed to eliminate the coupling between the loop of supply air temperature and that of thermal-space air temperature. The PID controller parameters are optimized by means of an improved genetic algorithm in floating point representations to obtain better performance. The population in the improved genetic algorithm mutates before crossover, which is helpful for the convergence. Additionally the micro mutation algorithm is proposed and applied to improve the convergence during the later evolution. To search the best parameters, the optimized parameters ranges should be amplified 10 times the initial ideal parameters. The simulation and experiment results show that the decoupling control system is effective and feasible. The method can overcome the strong coupling feature of the system and has shorter governing time and less over-shoot than non-optimization PID control.

VARIABLE STRUCTURE CONTROL OF AIRCRAFTFOR ATMOSPHERIC DISTURBANCE

Variable structure control (VSC) applied to atmospheric disturbance sup-pression is presented. The conditions are stipulated: the sliding mode existenee condi-tion, and invanance condition of atmospheric disturbanee in the variable structuresystem (VSS). A method of eigenstructure assignment technique for switching surfaeedesign is proposed. Based on different atmospheric disturbanee characteristics, such asrandom turbulence, discrete gust and wind shear, two kinds of control laws are derived that possess strong robustness. An example shows that this control approach isfeasible and effective.

Temperature Inversions,Meteorological Variables and Air Pollutants and Their Influence on Acute Respiratory Disease in the Guadalajara Metropolitan Zone,Jalisco,Mexico

The presence of temperature inversions (TI), concentration of air pollutants (AP) and meteorological variables (MV) affect the welfare of the population, creating public health problems (acute respiratory diseases ARDs, among others). The Guadalajara Metropolitan Zone (GMZ) experiences high levels of air pollution, which associated with the presence of temperature inversions and meteorological variations is conducive to the incidence of ARDs in children. The aim of this work is to evaluate the TI, MV, AP and their influence on the ARDs in children under five years in the GMZ from 2003 to 2007. In this period, the moderate and strong TI are the most frequent presenting from November to May. The AP shows a variable behavior during the year and between years, with the highest concentration of particles less than 10 microns (PM10), followed by ozone (O3), nitrogen dioxide (NO2), nitrogen oxides (NOX), carbon monoxide (CO) and sulfur dioxide (SO2), the most affected areas are the southeast of the GMZ. Annual arithmetic mean is 213,510 ± 41,209 ARDs consultations. The most important diseases are acute respiratory infections (98.0%), followed by pneumonia and bronchopneumonia (1.1%), asthma and status asthmaticus (0.5%) and streptococcal pharyngitis and tonsillitis (0.4%). Months with most inquiries were from October to March, mainly in the southeast, south and center of the city, coinciding with high levels of AP. Statistical analysis shows that the TI have significant correlation with ARDs in three years, temperature (Temp) in two, relative humidity (RH) in two, wind speed (WS) in three, wind direction (WD) in two, while that air pollutants NOX and NO2 showed significant correlation with ARDs throughout the period. CO and SO2 showed significance in two years, while the PM10 and O3 in one.

水冷式集中空调冷源系统多变量耦合物理模型

水冷式集中空调系统是一个多变量耦合的非线性系统,运行数据稀疏程度大,导致基于数据驱动的机器学习模型泛化能力差,全面反映水力与传热机理的物理模型成为当前研究的关键。然而,系统变量耦合复杂,迭代嵌套导致整体计算量消耗巨大,设备启停又导致管路水力结构变化而不得不频繁重构模型等技术难点亟待解决。利用离散变量连续化及模式搜索法,以阻力系数关联支路开度与设备启停,以水泵运行频率关联水泵启停与运行状态,实现将离散变量整合至连续变量,减少迭代嵌套,可实现流量动态分配、水力热力全局耦合计算。该研究构建了冷负荷、冷冻水流量、冷冻水供水温度、冷冻水供回水压差及环境温湿度为外部约束的水冷式集中空调冷源系统多变量耦合物理模型,实现对冷水机组台数、冷冻水泵台数与频率、冷却水泵台数与频率、冷却塔台数与频率等多个独立变量的异步调节。通过综合实验平台验证模型的可靠性,探究了不同工况下的机塔泵运行特性与群控策略。研究表明,冷源系统物理模型仿真结果平均相对误差小于10%,少部分在15%内,单次迭代计算耗时约0.32 s,多变量组合调节可综合权衡各子系统的能效,系统全局优化可最大限度挖掘节能空间,解决传统主观经验控制难以维持稳定节能效果的缺陷,为智能诊断提供理论基础。

考虑变掺氧富氧燃烧与利用LNG冷能的LAES的综合能源系统低碳经济调度

为促进风电消纳,减少火电机组的碳排放,解决综合能源系统(Integrated Energy System,IES)低碳经济运行问题,文中引入变掺氧富氧燃烧技术对燃气机组进行改造,并结合利用液化天然气(Liquefied Natural Gas,LNG)冷能的液化空气储能(Liquid Air Energy Storage,LAES),提出了一种电热气冷IES低碳经济优化策略。首先,构建含变掺氧富氧燃烧燃气机组、利用LNG冷能的LAES、电转气(Power To Gas,P2G)设备、中央空调和溴化锂制冷机的IES架构,并建立各设备的数学模型;其次,引入阶梯式碳交易机制,建立了以系统运行成本最小为目标的电热气冷IES低碳经济调度模型;最后,采用MATLAB调用GUROBI求解器对多个场景进行求解,验证了文中提出的低碳经济优化调度策略可以提高系统的风电消纳、有效降低系统运行成本,实现碳减排。

某有机化学实验室项目通风空调系统设计

有机化学实验往往会产生对人体有害的气体,有效的通风空调系统可以避免有害物泄漏,以保证实验人员在工作环境里的安全和健康。不同的有机化学实验室要求不同,其通风空调系统设计也有相应的不同要求。合成实验室通风量大,但对房间温湿度要求不高;分析仪器实验室中仪器设备较多,发热量较大,且对环境温湿度有一定的要求。本文结合某实际工程,对不同功能化学实验室通风量的确定、新风送风温度及空调设置情况和通风系统控制进行了介绍。

基于迭代学习的楼宇空调湿度控制研究

传统楼宇变风量空调控制方法,存在对被控系统数学模型的精度要求较高以及抗干扰能力弱的不足,因此限制了变风量空调系统的应用。针对变风量楼宇空调系统运行时存在的重复干扰与系统模型精度问题,采用迭代学习控制方法对变风量空调空气湿度进行控制。将变风量空调空气调节过程看成间歇过程,并且将室内空间湿度控制过程当作间歇过程对目标轨迹的跟踪问题,设计迭代学习控制器,使被控系统能够获得更好的精度和鲁棒性,实现变风量空调的高精度湿度轨迹跟踪。

基于变权物元可拓的中小机场空管运行安全态势评估

在建立了由人员因素、设备因素、环境因素、管理因素4个一级指标和16个二级指标的评估指标体系的基础上,根据层次分析法确定各指标的初始常权权重,引入变权向量后计算得到变权权重;结合物元可拓评估模型,得到量化的安全态势值。以某空管运行单位为例,得到的结果为“一般”,与专家评估结果和常权法模型评估结果相比较,证明了该评估模型的可行性,并且评估准确度优于传统模型。

过渡季节VAV空调系统送风温度的优化控制策略

变风量空调系统中,如何在良好室内空气品质与节能之间进行权衡一直是研究的难点.通过对多区域变风量空调及其控制系统进行分析研究,按照ASHRAE通风标准对新风量的要求,针对混和送风系统提出并在Trnsys仿真平台上分析了送风温度优化控制方案在不同负荷条件下的控制效果.研究结果表明,室外新风温度低于室内温度设定值时,送风温度的设定值受到设计风量和运行时刻各个空调区域风阀开度大小的限制.当过渡季节早晚的新风温度低于室内设定温度的工况时,若将送风温度由13,℃升高到16,℃,不但可以减少2.8%的空调系统能耗,而且有助于改善空气品质.

船用变风量空调系统解耦技术研究

分析变风量空调系统在船舶领域的发展现状和技术瓶颈,针对变风量空调系统中的多回路耦合问题,开展系统解耦及调控技术研究。解耦设计技术上,建立变风量空调系统多控制回路数学模型,在此基础上采用前馈补偿解耦方法进行解耦设计,经验证明显降低了控制回路间的耦合作用;调控技术上,创新提出多回路串联延时调控方法,经验证在未进行解耦设计的情况下仍能实现稳定调控,有利于工程实际应用。研究成果能够降低变风量空调系统调控难度,对促进变风量空调系统在船舶领域的应用具有积极意义。

MFAC和前馈补偿组合的VAV系统解耦控制仿真

在空调机风量优化控制的研究中,变风量(Variable Air Volume,VAV)系统存在多变量、耦合强烈、非线性及带有时延等特点。针对子系统耦合严重的现象,提出了无模型自适应控制(Model Free Adaptive Control,MFAC)和前馈补偿相结合方法,建立了两个空气处理机组成的耦合系统的数学模型,设计了MFAC控制器和前馈补偿解耦网络,对所建立的耦合系统进行了解耦控制。仿真结果表明:相对PID与前馈补偿组合解耦而言,无模型自适应控制配合前馈补偿的方法可以大幅减少调节时间,且超调量为0,具有很好的解耦效果,可以解决变风量系统的耦合问题。

VAV空调系统的动态建模及其送风机控制研究

介绍了VAV空调系统的动态建模过程,建立了压力无关型VAV末端的动态子模型,该模型能真实反映末端由于风阀联接机械迟滞、电动机动作过程、执行器不灵敏区等所引发的动态特性。以具有两个独立控制区域的小型家用VAV空调系统为对象,利用所建立的系统仿真模型,对两种不同的送风机控制方法进行比较研究。认为在小型家用VAV空调系统中,应当采用具有较弱比例控制作用的PI控制方法对送风机进行控制,以保证系统整体控制的稳定性,实现室温控制效果。