随着社会经济的迅速发展，人们对供水质量和供水系统可靠性的要求不断提高，

随着社会经济的迅速发展，人们对供水质量和供水系统可靠性的要求不断提高，再加上目前能源紧缺，利用先进的自动化技术、控制技术、以及通讯技术，设计高性能、高节能的变频恒压供水系统已成为必然趋势。
现在使用PLC和变频器来实现变频恒压供水已得到了广泛的应用。本论文根据居民生活用水的要求，而设计了一套基于西门子MM440型变频器的变频调速恒压供水控制系统，主要由可编程控制器、变频器、水泵机组、压力传感器等构成。
该系统通过压力传感器实时监测水流压力，经PID调节器调节后送入变频器进行变频调节，PLC根据变频器的输出信号来控制系统的3台泵运行，具有恒压供水及完善的保护和报警功能。实际应用结果表明，该变频恒压供水系统具有控制稳定可靠，自动化程度高，管理系统科学等特点；能达到降低成本、节约能源、减少设备损耗、提高城市供水质量的目的。

結果 (中文) 3:

With the rapid development of social economy, people's demand for water supply quality and reliability of water supply system is continuously improved, coupled with the current energy shortage, the use of advanced automation technology, control technology, and communication technology, design of high performance, high efficiency and constant pressure water supply system has become an inevitable trend. Now using PLC and inverter to achieve frequency conversion constant pressure water supply has been widely used. According to the requirements of the residents living water, this paper designs a series of constant pressure water supply control system based on SIEMENS MM440 type inverter, which is composed of programmable controller, frequency converter, water pump unit, pressure sensor and so on.
The system through the pressure sensor real-time monitoring of water pressure, the PID regulator to adjust the frequency converter to adjust, PLC according to the inverter output signal to control the system of 3 pump operation, with constant pressure water supply and improve the protection and alarm function. The practical application results show that the constant pressure water supply system has the characteristics of stable and reliable, high degree of automation, scientific management system, can achieve the purpose of reducing cost, saving energy, reducing the loss of equipment and improving the quality of urban water supply.