燕京理工学院
YANCHING INSTITUTE OF TECHNOLOGY
外文文献原稿和译文
学院：机电工程学院
专业：机械工程
学号：
姓名： 张磊
指导教师：王续明
2017 年 3 月
外文文献原稿和译文
原 稿
The water supply system is the national production and life indispensable important one annulus. The traditional method of water supply area, water pollution, infrastructure investment, but the main drawback is that water can not be kept constant, causing part of the equipment can not work normally. Variable frequency speed control technology is a
new mature AC motor stepless speed regulating technology, its unique excellent control performance is widely applied to the speed control field, especially in water supply industry. Due to the safety in production and the water quality of special needs, for constant pressure water supply with the stringent requirements, so the frequency control technology has been more in-depth application. Constant pressure water supply ways to advanced technology, constant pressure, convenient operation, reliable operation, energy saving, high degree of automation, in pump station water supply can perform the following functions:
(1) to maintain constant pressure;
(2) the control system can be manual or automatic operation;
(3) a plurality of pump automatic switch operation;
(4) system of sleep and wake, when people stop when water, the system is in a sleep state, until the water demand automatically wake;
(5) adjusts the PID parameters on line;
(6) pump unit and circuit protection detection alarm, signal display.
The actual pressure of the pipe network feedback and a given pressure were compared, when the pressure of a pipe network is low, increase the output of frequency converter, pump speed faster, water supply quantity increases, forcing the pipe network pressure rise. Vice pump speed slow down, reduce the water supply pipe network
pressure drop,, to keep the constant pressure water supply.
System hardware structure
System uses a pressure sensor, PLC and inverter as a central control device, to achieve a desired function. Source: network transmission and distribution equipment installation in pipe line pressure sensor, for detecting the water pressure of the pipe network, converting pressure is 4 ~ 20 mA current or voltage signal is 0 ~ 10V, supplied to the inverter.
Converter pump motor control device, in accordance with the constant water pressure needs to be 0 ~ 50 Hz frequency signal supply pump motor, adjust its speed SAJ converter is powerful, . pre-programmed set parameter set, will use the required in the process of setting the number of parameters is reduced to a minimum, default value according to the application parameter of the macro choice and different. The system adopts the PID control application macro, closed loop control. Inverter based on a constant pressure corresponding to the voltage setting value and from the pressure sensor to obtain the feedback current signal, the use of PID control macro automatically adjust, change the frequency output value to adjust the control the speed of the pump motor, to ensure that the pipe network pressure constant requirements.
The application of inverter in the constant pressure water supply
characteristic and analysis of variable frequency speed regulation
The water users in general is dynamic, so the water supply is insufficient or excess
water supply situation has occurred. The water supply and the imbalance between the concentrated reflection in water supply pressure, namely water and watersupply is less, the low pressure; less water consumption and water supply, the pressure. Keep the water pressure constant, can make the water supply and water balance between water supply and water for a long time, that is, less water when the water is less, so as to improve the quality of water supply.
Constant pressure water supply system for the user is very important. In production and living water, if water supply due to insufficient pressure or short of water, may affect the quality of life, serious when can influence the survival safety, such as when a fire occurs, if the water pressure is insufficient or water supply, can quickly fire, may cause significant economic losses and casualties. Therefore, water area by means of Arts is the constant pressure water supply system, can produce great economic benefit and social benefit.
With the development of electric power technology, frequency conversion technology perfected, with variable frequency speed control as the core of the intelligent water control system replaced the previous high level water tank and a pressure tank and water supply equipment, stable starting, the starting current can be limited within specified current, thereby avoiding the starting time of the impact of power grid; because the average rotational speed of pump is reduced, which can extend the pumps and valves and other things of life; to eliminate the start and stop of the water hammer effect. The stable and safe performance, simple and convenient operation, and complete and thoughtful function, will make the water supply and water conservation, energy saving, labor saving, ultimately achieve efficient operation.
application of variable frequency control constant pressure water supply mode
Usually in the same way in the water supply system, setting multiple common pump, water supply when the quantity of multi pump full open, water supply on one or two hours. In the variable frequency speed control for constant pressure water supply, in two ways, one is all pumps with a frequency converter; and each water pump with a frequency converter. After a method based on pressure feedback signal, operated by PID automatically adjusts the output frequency of the inverter, change the speed of the motor, eventually reaching the purpose of network voltage, a closed loop, is relatively simple, but the cost is high. The previous method of low cost, less than kind of poor performance, but the control program is complex, is the future direction of development, such as the Shanghai arts and science and technology of constant pressure water supply control system can realize a inverter control any number of motor function. The principle mentioned below are multiple motor inverter drive system.
PID control principle
According to the feedback principle: to maintain a physical quantity unchanged or essentially unchanged, it should bring the physical quantity and the constant comparison, to form a closed loop system. We want to keep the pressure constant, so we must introduce the hydraulic feedback value with a given value, thereby forming a closed loop system. But the control system is characterized by nonlinear, inertial system, now the control method combined with PID in the large pressure fluctuation, using fuzzy control, in order to accelerate the response speed in the pressure range; using PID to maintain static accuracy. This through the PLC and intelligent instrument can show the algorithm,
while the PLC programming to show when the pump frequency and inverter switching between. Practice has proved that, using this method is feasible, and the cost is not high.
control
Using frequency control to realize constant pressure water supply, with adjustable valve to realize constant pressure water supply, energy-saving effect is very significant (according to the specific circumstances calculated ). The utility model has the advantages of:
(1)Starting balance, the starting current can be limited within specified current, thereby avoiding the starting time of the impact of power grid;
(2)Because the average rotational speed of pump is reduced, thereby prolonging the service life of pump and valve etc.
(3)Can eliminate the start and stop of the water hammer effect;
Generally speaking, when performed by a frequency converter to control a motor, just make the inverter motor capacity and the actual capacity of the motor can be. When one inverter control two motors, principle of inverter motor capacity should be equal to the capacity of the two motors. But if the peak load of water more than two pumps at full supply a lot of difference, Shanghai arts and science and technology engineers suggested, may be considered appropriate to reduce the capacity of the frequency converter, but attention should be paid to leave enough capacity.
Although the pump at low speed, small working current of the motor. However, when the user with the water volume changes frequently, the motor will be in frequent ascending, descending and ascending, descending speed state, the current speed slightly over the motor rated current, cause the motor overheat. Therefore, the motor thermal protection is required. For this due to frequent ascending, descending speed and accumulated temperature rise, frequency converter in electronic thermal protection function is difficult to play a protective role, so should be used in thermal relay for motor thermal protection.
The main function of preset, the highest frequency should be rated motor frequency converter the highest working frequency. Ascending, descending speed time in using PID regulator case, ascending, descending velocity time should be set to be short, so as not to affect the PID adjuster determines the dynamic response process. Such as the frequency converter with PID regulation function, as long as the preset set PID function effectively, the setting of the acceleration and deceleration time will automatically lapse.
译 文
供水系统是国民生产生活中不可缺少的重要一环。传统供水方式占地面积 大，水质易污染，基建投资多，而最主要的缺点是水压不能保持恒定，导致部分设备不能正常工作。变频调速技术是一种新型成熟的交流电机无极调速技术，它以其独特优良的控制性能被广泛应用于速度控制领域，特别是供水行业中。由于安全生产和供水质量的特殊需要，对恒压供水压力有着严格的要求，因而变频调速技术得到了更加深入的应用。恒压供水方式技术先进、水压恒定、操作方便、运行可靠、节约电能、自动化程度高，在泵站供水中可完成以下功能：
（1）维持水压恒定；
（2）控制系统可手动/自动运行；
（3）多台泵自动切换运行；
（4）系统睡眠与唤醒，当外界停止用水时，系统处于睡眠状态，直至有用水需求时自动唤醒；
（5）在线调整PID参数；
（6）泵组及线路保护检测报警，信号显示等。
将管网的实际压力经反馈后与给定压力进行比较，当管网压力不足时，变频器增大输出频率，水泵转速加快，供水量增加，迫使管网压力上升。反之水泵转速减慢，供水量减小，管网压力下降，保持恒压供水。
工作原理
在供水系统中引进变频器结合小型PLC技术，不仅改变传统用阀门控制水量多少，而且在节能、恒压控制等方面均有非常好的效果，本文介绍了变频器--PLC调控技术在水泵控制中的应用。 控制系统用一台变频器可以带三台水泵，每台水泵既可以工作在常规工频泵模式，也可以工作在变频泵模式。每台泵只能处于变频或工频其中一种工作模式，通过两个继电器互锁保证它的安全与可靠。
生活用水中的压力变送器将水的压力信号传输到调节器，根据与调节器的设定值和报警上下限比较，送信号给PLC与变频器，系统的起停泵分别由调节器的压力下限信号和变频器的频率下
限信号决定，假如压力低，调节器给PLC一个压力下限信号，PLC启动变频器，并使一号泵处于变频工作状态， 输出的频率逐渐增大，经过一段时间的调节，如压力还低，这时，PLC让一号泵处于工频状态工作，使二号泵处于变频工作状态泵，如压力还低，则让二号泵处于工频状态工作，使三号泵处于变频工作状态，如此类推。当压力达到调节器上限报警值时，调节器输出降低，变频器频率降低，低到频率下限设定值，这时变频器给出一个频率下限信号给PLC，PLC根据先启先停的原则控制泵的运行顺序，例如，PLC收到频率下限信号时， 系统中泵的状态是一号工频，二号工频，三号变频，这时一号泵最先启动，所以先停，接着如压力还高，则停二号泵。系统采用了每次都进行低速启动，高速运行以提高运行效率。
系统硬件构成
系统采用压力传感器、PLC和变频器作为中心控制装置，实现所需功能。 来源:输配电设备网安装在管网干线上的压力传感器，用于检测管网的水压，将压力转化为4～20 mA的电流或者是0~10V的电压信号，提供给变频器。 变频器是水泵电机的控制设备，能按照水压恒定需要将0～50 Hz的频率信号供给水泵电机，调整其转速SAJ变频器功能强大，即预先编置好的参数集，将使用过程中所需设定的参数数量减小到最小，参数的缺省值依应用宏的选择而不同。系统采用PID控制的应用宏，进行闭环控制。变频器根据恒压时对应的电压设定值与从压力传感器获得的反馈电流信号，利用PID控制宏自动调节，改变频率输出值来调节所控制的水泵电机转速，以保证管网压力恒定要求。
变频器在恒压供水中的应用
一、 变频调速的特点及分析
用户用水量一般是动态的，因此供水不足或供水过剩的情况时有发生。而用水和供水之间的不平衡集中反映在供水的压力上，即用水多而供水少，则压力低；用水少而供水多，则压力大。
保持供水压力的恒定，可使供水和用水之间保持平衡，即用水多时供水也多，用水少时供水也少，从而提高了供水的质量。 恒压供水系统对于用户是非常重要的。在生产生活供水时，若自来水供水因故压力不足或短时断水，可能影响生活质量，严重时会影响生存安全，如发生火灾时，若供水压力不足或或无水供应，不能迅速灭火，可能引起重大经济损失和人员伤亡。所以，用水区域采用正艺恒压供水系统，能产生较大的经济效益和社会效益。 随着电力技术的发展，变频调速技术的日臻完善，以变频调速为核心的智能供水控制系统取代了以往高位水箱和压力罐等供水设备，起动平稳，起动电流可限制在额定电流以内，从而避免了起动时对电网的冲击；由于泵的平均转速降低了，从而可延长泵和阀门等东西的使用寿命；可以消除起动和停机时的水锤效应。其稳定安全的运行性能、简单方便的操作方式、以及齐全周到的功能，将使供水实现节水、节电、节省人力，最终达到高效率的运行目的。
二、 恒压供水的变频应用方式
通常在同一路供水系统中，设置多台常用泵，供水量大时多台泵全开，供水量小时开一台或两台。在采用变频调速进行恒压供水时，就用两种方式，其一是所有水泵配用一台变频器；其二是每台水泵配用一台变频器。后种方法根据压力反馈信号，通过PID运算自动调整变频器输出频率，改变电动机转速，最终达到管网恒压的目的，就一个闭环回路，较简单，但成本高。前种方法成本低，性能不比后种差，但控制程序较复杂，是未来的发展方向，比如上海正艺科技的恒压供水控制系统就可实现一变频器控制任意数马达的功能。下面讲到的原理都是一变频器拖动多马达的系统。
三、 PID控制原理
根据反馈原理：要想维持一个物理量不变或基本不变，就应该引这个物理量与恒值比较，形成闭环系统。我们要想保持水压的恒定，因此就必须引入水压反馈值与给定值比较，从而形成闭
环系统。但被控制的系统特点是非线性、大惯性的系统，现在控制和PID相结合的方法，在压力波动较大时使用模糊控制，以加快响应速度；在压力范围较小时采用PID来保持静态精度。这通过PLC加智能仪表可时现该算法，同时对PLC的编程来时现泵的工频与变频之间的切换。实践证明，使用这种方法是可行的，而且造价也不高。
四、 变频控制原理
用变频调速来实现恒压供水，与用调节阀门来实现恒压供水相比，节能效果十分显着（可根据具体情况计算出来）。其优点是：
1、 起动平衡，起动电流可限制在额定电流以内，从而避免了起动时对电网的冲击；
2、 由于泵的平均转速降低了，从而可延长泵和阀门等的使用寿命；
3、 可以消除起动和停机时的水锤效应；
一般地说，当由一台变频器控制一台电动机时，只需使变频器的配用电动机容量与实际电动机容量相符即可。当一台变频器同时控制两台电动机时，原则上变频器的配用电动机容量应等于两台电动机的容量之和。但如在高峰负载时的用水量比两台水泵全速供水量相差很多时，上海正艺科技的工程师建议，可考虑适当减小变频器的容量，但应注意留有足够的容量。
虽然水泵在低速运行时，电动机的工作电流较小。但是，当用户的用水量变化频繁时，电动机将处于频繁的升、降速状态，而升、降速的电流可略超过电动机的额定电流，导致电动机过热。因此，电动机的热保护是必需的。对于这种由于频繁地升、降速而积累起来的温升，变频器内的电子热保护功能是难以起到保护作用的，所以应采用热继电器来进行电动机的热保护。
在主要功能预置方面，最高频率应以电动机的额定频率为变频器的最高工作频率。升、降速时间在采用PID调节器的情况下，升、降速时间应尽量设定得短一些，以免影响由PID调节器决定的动态响应过程。如变频器本身具有PID调节功能时，只要在预置时设定PID功能有效，则所设定的升速和降速时间将自动失效。
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