采用PLC控制的变频恒压供水系统设计

发布时间：2019-02-12 18:40

【摘要】：伴随着中国经济的飞速发展,工矿企业生产规模不断扩大,企业用水量不断增加,供水管网规模逐年扩大,生产流程控制精度要求逐年提升,工业企业供、用水系统管理取得了长足的发展。与此同时,现代大工业生产对于供水系统的软、硬件设施标准及供水系统性能指标、质量都提出了新的、更高的要求。工业企业供水系统的安全性、经济性、可靠性直接影响企业生产的安全、连续,也直接体现企业精细化管理水平。而传统的恒速泵加压供水、高位水箱供水等供水方式普遍存在供水可靠性不高、能量转化效率低下、系统控制自动化程度不高、一线工人劳动强度大、设备控制参数调整不及时等缺点,难以满足当前大工业生产对供水安全及供水质量的要求。论文依据大连某石油化工企业实际用水需求参数,采用低压电控设备、变频器、PLC控制器、压力表及变送器、电动机水泵机组、后台监控计算机等设备组成、具备最低安全供水量保证的自动变频恒压供水系统。该系统既能通过电动机异常停机自动互投备用,保证系统最低安全用水量；又能通过变频电动机自动投切,实现大流量供水时的变频恒水压运行。有效地解决传统供水方式中存在的缺点,具有较高的供水可靠性和明显的节能效益。系统采用通过后台计算机的远程监控功能,提高了系统的自动化程度和故障异常处置效率,加强了生产运行受控管理水平,大幅降低一线工人劳动量。首先,该论文依据电动机输出功率与水泵转速三次方成正比的理论基础,分析了变频恒压供水系统的节能原理,建立了系统控制模型和近似数学模型。通过配置变频器内置PID模块实现调速系统的闭环控制。供水全流量采用工频机泵互投保安供水和变频机泵分级调节供水相结合的模式,达到既能保证最低安全供水流量又能高流量恒压供水且节能的目的。其次,该论文论述了采用两电动机互投备用提供最低保安供水量设计理念的原因及实现手段,论述了四台水泵机组并联供水模式下的各种有效供水状态以及切换条件,研究了电动机由变频切工频运行的转换过程、存在的问题以及应对措施,提出了PLC控制软件程序流程和电气控制方案。对PLC软件编程以及PID参数设置和电动机继电保护定值设定等问题进行了深入的探讨。最后,通过研究计算机和PLC之间的通信及其硬件连接,探讨了计算机通信、监控网络的软硬件设置,并利用设备内置通信模块实现供水系统远程监控和故障报警功能。
[Abstract]:With the rapid development of China's economy, the production scale of industrial and mining enterprises is expanding, the water consumption of enterprises is increasing, the scale of water supply network is expanding year by year, the precision of production process control is being improved year by year, and the supply of industrial enterprises is increasing year by year. Water system management has made great progress. At the same time, modern large-scale industrial production has put forward new and higher requirements for the quality of water supply system, such as the standard of software and hardware facilities and the performance index of water supply system. The safety, economy and reliability of water supply system in industrial enterprises directly affect the production safety of enterprises. But the traditional constant speed pump pressurized water supply, high water tank water supply and other water supply methods generally have low reliability of water supply, low efficiency of energy conversion, low degree of automation of system control, and high labor intensity of workers on the first line. It is difficult to meet the requirements of water supply safety and water supply quality in large industrial production because the adjustment of equipment control parameters is not timely and so on. According to the actual water demand parameters of a petrochemical enterprise in Dalian, the paper adopts low voltage electronic control equipment, frequency converter, PLC controller, pressure gauge and transmitter, motor pump unit, background monitoring computer and other equipment. Automatic variable frequency constant pressure water supply system with minimum safe water supply guarantee. The system can not only automatically switch on each other through abnormal stop of motor to ensure the lowest safe water consumption of the system, but also realize the operation of variable frequency constant water pressure when large flow water supply is realized by automatic switching of variable frequency motor. It can effectively solve the shortcomings of traditional water supply, and has higher reliability of water supply and obvious benefit of energy saving. By using the remote monitoring function of backstage computer, the system improves the automation degree of the system and the efficiency of abnormal handling of faults, strengthens the level of controlled management in production and operation, and greatly reduces the labor load of the front-line workers. Firstly, based on the theory that the output power of the motor is proportional to the third power of the pump speed, the energy saving principle of the variable frequency constant pressure water supply system is analyzed, and the control model and approximate mathematical model of the system are established. The closed loop control of the speed regulation system is realized by configuring the PID module of the inverter. The total flow of water supply is based on the combination of power frequency machine and pump mutual input and security water supply and variable frequency machine pump grading regulation and water supply, which can not only guarantee the minimum safe water supply flow, but also ensure the high flow constant pressure water supply and save energy. Secondly, the paper discusses the reasons and means of using two motors to supply the lowest security water supply, and discusses the effective water supply state and switching conditions under the parallel water supply mode of four water pump units. This paper studies the conversion process, existing problems and countermeasures of the motor running from frequency conversion to power frequency, and puts forward the program flow of PLC control software and the electric control scheme. The programming of PLC software, the setting of PID parameters and the setting of relay protection of motor are discussed. Finally, by studying the communication between computer and PLC and its hardware connection, this paper discusses the hardware and software settings of computer communication and monitoring network, and realizes the remote monitoring and fault alarm function of water supply system by using the built-in communication module of the equipment.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP273;TU991.4

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