基于PLC的变频调速恒压供水系统设计与实现

发布时间：2018-08-09 15:07

【摘要】：社会经济的不断发展，带来的结果就是城市的不断扩展。而随着城市常驻人口的增多和人们生活水平的不断提高，人们对城市供水系统的质量、数量和稳定性要求也越来越高。相比之下，我国的一些中小城市的水厂，特别是一些老旧水厂的自动控制系统的性能落后，相应机组的控制还主要依靠人工操作来完成。这样就使得系统的控制过程比较繁琐，同时，手动控制难以对供水管网的压力和水位变化作出及时的相应。所以，为了保证对城市的供水，这些供水系统通常都是超压状态运行，不仅效率低下，同时也使得城市管网的曝损比较严重。在这种状况下，本文考虑到我国中小城市供水系统的状况，对基于PLC的变频调速恒压自动控制供水系统进行设计。在所有的变频调速恒压供水系统中，对于单台水泵工作状况的调节，主要通过变频器对电源频率的改变来实现对电机转速的控制，进而实现对水泵性能曲线的改变。通过对水平工作状况能耗图的深入分析，可以发现，要利用变频调速来实现供水系统的恒压，在转速降低的情况下，流量跟水泵的转速成正比，而系统功率则以转速的3次方下降，跟传统供水方式中通过阀门来实现节流的方式相比，变频调速恒压系统的能量损耗更少，从而实现能量的节约。在本文的控制系统中，所采用的编程软件主要为德国Simens公司的STEPMicro Win平台，对供水系统中用于压力控制的PID控制进行了详细设计，该PID控制器在设计上内置于PLC中。通过该控制器，能够实现对压力给定值和测量值的偏差进行处理，对变频器的输出电压和频率进行实时控制，通过对水泵电动机的转速的改变来对水泵的出水口流量进行调节，从而实现了对管网压力的自动调节，最终将管网压力稳定在预先设定的量值附近。此外，还根据软件工程理论中的设计规范对PLC平台进行系统分析和设计，制定了软件的具体功能需求，在此基础上，对整个系统的框架和界面进行了设计。通过对整个系统的实际运行和调试，能够实现对供水过程的自动化控制，在此基础上还可以有效降低能耗，从而确保了供水系统在最佳的运行状态运行。系统具有安装维护方便、运行稳定、可靠、功能齐全、人机界面友好和使用方便的特点。
[Abstract]:With the continuous development of social economy, the result is the continuous expansion of the city. With the increase of resident population and the improvement of people's living standard, the quality, quantity and stability of urban water supply system are becoming more and more important. In contrast, the performance of automatic control system in some small and medium-sized cities of our country, especially some old water plants, is backward, and the control of corresponding units is mainly accomplished by manual operation. This makes the control process of the system more cumbersome, at the same time, manual control is difficult to make timely response to the pressure and water level change of the water supply network. Therefore, in order to ensure the water supply to the city, these water supply systems are usually operated under overpressure, which is not only inefficient, but also causes serious exposure of urban pipe network. Under this condition, considering the situation of water supply system in medium and small cities of our country, this paper designs the constant pressure automatic control water supply system based on frequency conversion speed regulation based on PLC. In all the variable frequency speed regulating constant pressure water supply system, the control of motor speed and the change of pump performance curve are mainly realized by changing the frequency of inverter to the frequency of power supply to adjust the working condition of a single pump. Through the deep analysis of the energy consumption diagram of the horizontal working condition, it can be found that the constant pressure of the water supply system should be realized by frequency conversion speed regulation, and the flow rate is proportional to the speed of the pump when the speed of the pump is reduced. The power of the system is reduced to the third power of the rotational speed. Compared with the traditional way of water supply, the energy loss of the constant pressure system is less than that of the traditional way of water supply, so the energy can be saved. In the control system of this paper, the programming software used in this paper is mainly STEPMicro Win platform of Simens Company of Germany. The PID control for pressure control in water supply system is designed in detail. The PID controller is built into PLC in design. Through the controller, the deviation between the given pressure value and the measured value can be processed, the output voltage and frequency of the inverter can be controlled in real time, and the flow rate of the pump outlet can be adjusted by changing the speed of the pump motor. Thus, the automatic adjustment of pipe network pressure is realized, and the network pressure is stabilized near the preset value. In addition, the PLC platform is systematically analyzed and designed according to the design specifications of the software engineering theory, and the specific functional requirements of the software are formulated. On this basis, the framework and interface of the whole system are designed. Through the actual operation and debugging of the whole system, the automatic control of the water supply process can be realized, and on this basis, the energy consumption can be effectively reduced, thus ensuring the operation of the water supply system in the best running state. The system has the characteristics of convenient installation and maintenance, stable operation, reliable, complete function, friendly man-machine interface and convenient use.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU991

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