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1、外文资料翻译Water Tower Water Level Control System Research And Design Abstract: The water tower is a water level control system for residential quarters of Chinas extensive use of the water supply system, the existence of the traditional control methods to control the accuracy of the low power consumptio
2、n of the shortcomings of large, research-based PLC controlled multi-pump cycle frequency constant pressure water supply system, using programmable logic controller, inverter, as well as devices such as pressure transmitter, complete logic control, speed control and data sampling frequency and other
3、functions, allowing the system to achieve automatic control, to achieve the purpose of energy conservation, improve the quality of the water supply system. Key words: PLC, inverter,constant pressure water supply 0 Introduction Water tower water level control system is the wider use of residential qu
4、arters of Chinas water supply system, water supply systems in most of the traditional use of water towers, water tanks, or high pressure tank pressurization equipment to pump water higher than the actual height of the head to upgrade of water, the the result of increased water pump shaft power and e
5、nergy consumption. Research and design of the towers is the water level control system uses a 1 constant pressure water supply system, stepless speed pumps. Automatically based on changes in water-conditioning system operating parameters to maintain a constant pressure to meet the water requirements
6、 of todays advanced, energy-saving and reasonable water supply system 1. Pump started, pid controller pressure transmitter to the control point to provide the pressure signal, when the pressure point is not equal to set value, pid controller by adjusting the inverter output frequency to change the p
7、ump speed to regulate the pipeline pressure constitutes a closed-loop feedback control system, water pressure regulator so that users timely, small fluctuations in results. And in the process control system designed to take full account of the principle of load balancing, to take first-in-first out
8、strategy of lining up, the way the implementation of the rotating frequency to ensure that the basic balance of the water usage. 1 Frequency Control Constant Pressure Water Supply Principle Frequency Control Constant Pressure Water Supply System by the programmable logic controller (plc), converter
9、(built-pid), pressure transmitter, low-voltage electrical and pump components, such as Figure 1. Map m1 m3 for water pump motors, p1 p3 for pumps, km1 km6 for motor starting and stopping each of the AC contactor switch. Basic working principle of the system: by the plc a signal to the inverter to co
10、ntrol the water cycle work, when the large volume of water consumed by the plc control of all water line installed in the outlet pipe of the pressure transmitter, pressure standard signals into dc 0 v 10 v into the analog signal converter with pid regulator, pressure settings and pressure feedback v
11、alues after the implementation of pid calculated values of the output of a frequency converter to set the value for the pump by the inverter to provide variable frequency electrical power to realize stepless speed regulation of electric pumps to regulate the exit of the water supply pipe network pre
12、ssure, constant pressure water supply to achieve the purpose. Pressure feedback signal in order to ensure an accurate value, yet the value of feedback signal to set the filter time constant. The scope of the power converter, Figure 1 can increase the number of the motor to achieve a multi-trailers,
13、Optimization of the program. 2 towers of water level control system design Frequency according to the principle of constant pressure water supply system the design water level control system of the water tower block diagram shown in Figure 2, the city water network eq with the water level controller
14、 to control the injection valve yv1, as long as the water level below the high water mark, then to the pool water automatically. Pool of high / low water level signal directly to the plc, as a high / low level alarm. In order to ensure continuity of supply, the water level of the smaller distance be
15、tween the upper and lower limits. Domestic water and fire water pump three shared 3, usually yv2 solenoid valve in a state of loss, the closure of the fire pipe network, when a fire occurs, the solenoid valve was yv2 electricity, water distribution network with the closure of life, three water pumps
16、 for fire use, and maintain high-pressure fire water value. After the lifting of the fire, three use domestic water pump replaced and the cycle of operation, to maintain constant low water value. Each pump motor can run frequency, and frequency can be run. When the small volume of water consumed, a
17、water pump under the control of the converter stable operation of large quantities of water to the pump when running at full speed there is no guarantee that the pressure on network stability, plc pressure given the lower limit of the inverter signal and high-speed signal at the same time plc was de
18、tected, plc automatically work in the original state of the pump frequency into frequency operation, in order to maintain the continuity of pressure at the same time use the next pump put into operation after start-up converter in order to increase the supply pipe network pressure of water to ensure
19、 stability; if running two pumps can not meet the requirements of the pressure, the frequency of work will be followed by a state into the pump-frequency operation, and then pump into a variable frequency operation; when the water consumption reduction, the first performance inverter has been workin
20、g effectively at the lowest speed signals, when the pressure signal, such as the ceiling is still there, plc will be the first first run of the pump frequency to quit in order to reduce the volume of water supplied, when the two signals when there are still, plc and then quit second frequency of the
21、 pump to run until a constant pressure water supply pump with frequency converter. All pump motors start from a stop to and from the start to stop by the inverter to control to achieve soft-start with set, to avoid the start of high-current impact to the pump motor to extend the life of the motor. A
22、t the same time, the use of variable frequency operation of the system pumps water cycle in order to first to open the first gate of the order of related pumps, so that both the water supply system to ensure back-up water pumps, water pumps and the system have the same running time as effective in p
23、reventing back-up pump death occurred not long-term phenomenon of rust and improve the comprehensive utilization rate of equipment, reducing maintenance costs. Electrical control system main circuit see Figure 3. AC contactor km1, km3, km5 were three pump motor control m1, m2, m3 frequency operation
24、; AC contactor km2, km4, km6 respectively control m1, m2, m3 of Frequency operation; fr1, fr2, fr3 thermal relay for protection of the three pump motor overload; qs1, qs2, qs3, qs4 respectively, and three pump motor inverter main circuit isolation switch; fu1 fu3 mainly The fuse circuit. The system
25、works in manual mode, plc alarm detection only by the artificial adoption of panel buttons and switches From water pumps to stop and switch; the system works in automatic mode, all controlled by the plc completed report to the police. 3 towers of water level control system software design The main f
26、unction of the automatic control system is achieved through software in light of the foregoing 1 control constant pressure water supply system requirements, water towers of the main process control system shown in Figure 4. Use of the timer interrupt function of the realization of pid control regula
27、r sampling and output control, three pumps to generate switching signals, the signal contacts of the integrated logic control and alarm handling by the program. In program design to take full account of the principle of load balancing, to take first-in-first out strategy of lining up, the way the im
28、plementation of the rotating frequency to ensure that the basic balance of the water usage. Constant pressure of life and fire of the two pairs of constant digital value is used directly in the proceedings set. Life when the water supply system for the full-scale settings of 70%, when the fire water
29、 supply system for the full-scale settings of 90%. Pid loop gain and time constant is initially set at: gain kc = 0.25, sampling time ts = 0.2 s, integration time ti = 30 min. in accordance with specific conditions need to be further adjusted in order to achieve optimal control. To a constant water
30、supply, landing in the water pressure to increase the inverter output frequency, when the maximum frequency converter and a constant pressure pump can not meet the requirements, while running the pump frequency to switch to the running frequency, At the same time need to start a second frequency or
31、third pump until the water supply to meet the requirements. Need to determine criteria for the launch of a new water pump is the inverter output frequency is set to reach the upper limit. In order to determine the frequency of the inverter limits the accuracy of least squares by chance should be the
32、 frequency of the frequency of fluctuations in the ceiling from the situation. Inverter control motor pumps are activated each time the soft-start, and requires the use of water pumps must turn to serve as a continuous variable frequency pump operation shall not exceed 3 h, each time when the need t
33、o launch a new water pump, the pump will run from the existing removal of the inverter, and replace the power-frequency operation, reset the inverter and run the pump for a new start. Three pumps to control the duty cycle is the use of pump No. 1 way to achieve (to 3 in the plus 1 equal to zero), or
34、 combined with the total number of pump pump pump rotation to achieve its work. 4 Concluding remarks In this paper, the design of the towers the water level control system uses a programmable logic controller, inverter based on changes in water pressure transmitter through the pid to realize steples
35、s speed variable frequency drive pump motor in the water changes to maintain constant water pressure meet the water requirements, so as to achieve the purpose of constant pressure water supply. In the process control system designed to take full account of the principle of load balancing, to take fi
36、rst-in-first out strategy of lining up, the way the implementation of the rotating frequency to ensure that the basic balance of the water usage. Frequency Constant Pressure Water Supply to change the supply of the previous quantitative methods to achieve DAMA principle, constant pressure water supp
37、ly frequency mode thus saving energy, easy to operate, high degree of automation.水塔水位控制系统的研究与设计摘要:水塔水位控制系统是我国住宅小区广泛应用的供水系统,传统的控制方式存在控制精度低、能耗大的缺点,研究设计的基于PLC控制的多泵循环变频恒压供水系统,采用可编程序控制器、变频器以及压力变送器等器件,完成逻辑控制、变频调速和数据采样等功能,使系统实现自动控制,达到节能的目的,提高了供水系统的质量。关键词:可编程控制器;变频器;恒压供水0引言水塔水位控制系统是我国住宅小区广泛应用的供水系统,传统供水系统大多采
38、用水塔、高位水箱或气压罐式增压设备,用水泵以高出实际用水高度的扬程来“提升”水量,其结果增大了水泵的轴功率和能耗。现研究设计的水塔水位控制系统采用变频调速恒压供水系统,实现水泵无级调速。依据用水量的变化自动调节系统的运行参数,保持水压恒定以满足用水要求,是当今先进、合理的节能型供水系统1。水泵启动后,压力变送器向PID控制器提供控制点的压力信号,当该点的压力不等于设定值时,PID控制器通过调节变频器的输出频率以改变水泵的转速来调节管道压力,构成闭环反馈控制系统,因此用户水压调节及时,波动小,效果良好。并在控制系统的程序设计中充分考虑到负载均衡性原则,采取“先入先出”的排队策略,执行变频方式轮值
39、,确保各水泵使用率基本均衡。1变频调速恒压供水系统的原理变频调速恒压供水系统主要由可编程控制器(plc)、变频器(内置pid)、压力变送器、低压电器及水泵等组成见图1.图中m1m3为水泵电机,p1p3为水泵,km1km6为电机起、停及互相切换的交流接触器。系统基本工作原理:由plc向变频器发出信号,控制水泵循环工作,当用水量大时,由plc控制全部水安装在出水管网上的压力变送器,将压力信号转换成标准的dc0v10v的模拟量信号送入变频器内的pid调节器,压力设定值与压力反馈值进行比较后,经pid计算输出一个执行值作为变频器的频率给定值,由变频器为水泵电机提供可变频率的电源,实现水泵电机的无级调速
40、,调节管网出口处供水压力,达到恒压供水目的。为了保证水压反馈信号值的准确、不失值,对反馈信号设置滤波时间常数。在变频器功率范围内,图1中的电机数量可以增加,实现“一拖多机”的优化方案。2水塔水位控制系统的设计按变频调速恒压供水系统原理设计的水塔水位控制系统框图如图2所示,市网自来水用水位控制器eq来控制注水阀yv1,只要水位低于高水位,则自动往水池注水。水池的高/低水位信号也直接送给plc,作为高/低水位报警。为了保证供水的连续性,水位的上下限距离较小。生活用水和消防用水共用三台水泵3,平时电磁阀yv2处于失电状态,关闭消防管网,当火灾发生时,电磁阀yv2得电,关闭生活用水管网,三台水泵供消防
41、用水使用,并维持消防用水的高压值。火灾解除后,三台水泵改为生活用水使用,并循环运行,维持生活用水的低恒压值。每台水泵电机既可以变频运行,又可以工频运行。当用水量较小时,一台水泵在变频器的控制下稳定运行,当用水量大到水泵全速运行也不能保证管网的压力稳定时,plc给定的压力下限信号与变频器的高速信号同时被plc检测到,plc自动将原工作在变频状态下的水泵投入到工频运行,以保持压力的连续性,同时将下一台水泵用变频器起动后投入运行,以加大管网的供水量保证压力稳定;若两台水泵运转仍不能满足压力的要求,则依次将变频工作状态下的水泵投入到工频运行,再将一台水泵投入变频运行;当用水量减少时,首先表现为变频器已
42、工作在最低速信号有效,这时压力上限信号如仍出现,plc首先将最先工频运行的水泵停掉,以减少供水量,当上述两个信号仍存在时,plc再停掉第二台工频运行的水泵,直到最后一台泵用变频器恒压供水。所有水泵电机从停止到启动及从启动到停止都由变频器来控制,实现带载软启动,避免了启动大电流给水泵电机带来冲击,延长了电机的使用寿命。同时系统供水采用变频运行水泵循环方式,以“先开先关”的顺序关水泵,这样,既保证供水系统有备用水泵,又保证系统水泵有相同的运行时间,有效地防止因为备用水泵长期不用发生锈死现象,提高了设备的综合利用率,降低了维护费用。电气控制系统主电路见图3.交流接触器km1、km3、km5分别控制三
43、台水泵电机m1、m2、m3的工频运行;交流接触器km2、km4、km6则分别控制m1、m2、m3的变频运行;fr1、fr2、fr3是热继电器,用于保护三台水泵电机的过载;qs1、qs2、qs3、qs4分别为变频器和三台水泵电机主电路的隔离开关;fu1fu3为主电路的熔断器。该系统工作于手动状态时,plc只进行检测报警,由人工通过面板上的按钮和开关进行水泵的起、停和切换;该系统工作于自动状态时,所有控制、报警均由plc完成。3水塔水位控制系统的软件设计系统的自动控制功能主要是通过软件来实现的,结合前面所述变频调速恒压供水系统的控制要求,水塔水位控制系统的主程序流程见图4.利用定时器中断功能实现p
44、id控制的定时采样及输出控制,三台水泵切换信号的生成、接触器逻辑控制信号的综合及报警处理等都由程序控制。在程序设计时充分考虑到负载均衡性原则,采取“先入先出”的排队策略,执行变频方式轮值,确保各水泵使用率基本均衡。生活及消防双恒压的两个恒定值是采用数字式方式直接在程序中设定的。生活供水时系统设定值为满量程的70%,消防供水时系统设定值为满量程的90%.pid回路增益和时间常数初步设定为:增益kc=0.25、采样时间ts=0.2s、积分时间ti=30min.根据具体情况需进一步调整以达到最优的控制效果。为了恒定供水,在水压降落时要升高变频器的输出频率,当变频器达到上限频率且一台水泵还不能满足恒压
45、要求时,则把变频运行的水泵切换到工频上运行,同时需要变频启动第二台或第三台水泵,直到满足供水要求。判断需不需要启动新水泵的标准就是变频器的输出频率是否达到设定的上限值。为了判断变频器工作频率达上限值的准确性,应滤去偶然的频率波动起的频率达到上限的情况。变频器控制水泵电机的每一次启动均为软启动,并规定各台水泵必须交替使用,任一台泵连续变频运行不得超过3h,因此每次需启动新水泵时,将现行运行的水泵从变频器上切除,并换上工频电源运行,将变频器复位并用于新运行水泵的启动。三台水泵的工作循环控制是使用水泵号加1的方法实现(到3在加1时等于零),即用水泵的总数结合水泵号实现水泵的轮换工作。4结束语本文研究设计的水塔水位控制系统采用可编程控制器、变频器依据用水量的变化通过pid压力变送器来实现变频驱动水泵电机无级调速,在用水量发生变化时保持水压恒定以满足用水要求,从而达到恒压供水的目的。控制系统在程序设计时充分考虑到负载均衡性原则,采取“先入先出”的排队策略,执行变频方式轮值,确保各水泵使用率基本均衡。变频恒压供水改变了以往的定量供给方式,实现“按需分配”原则,因此变频恒压供水方式节省能源、操作方便、自动化程度高。