Design And Realize Of The Variable-pressure Variable-flow Water Supply System Based On Fuzzy Control

The goal of this project is to design a control system for the implementation of urban water supply program. The water level in cistern and the pressure of the lowest utilization ratio water point for the urban people's water supply as the final control object, the overall coordinated control on the diversion water of long-range water supply wells and water supply for variable frequency pump to make it run on the most reasonable, the most energy-efficient and the most efficient circumstances, to ensure the cistern water level is the most reasonable and meet demand of the lowest utilization ratio water point. The realization of the system will greatly enhance the automation of the remote water conveyance and ensure water quality.This system used the German Siemens PLC (Programmable Logic Controller) s7200 as a field measurement and control equipment, PLCs7-300 with MPI interface was selected as based station, which dynamic allocate a address for each site, the information were exchange between scattered site in the scheduled period , using Simatic WinCC as upper supervision software. S7200 booster pumping station collected inverter's state, pressure, flow, water level information, etc. in each information cycle, the information sent to the host computer and PC optimization of the signal sent back to control the start-stop and speed of each pumps. PLC of master station communicated with four single well slave stations by radio station, a multilevel remote distributed control system was formed. Master station control the start-stop of the pump through the control of cistern water level.In the variable-pressure variable-flow water supply system, according to the difficulty in establish mathematical model of the object accurately, the system has characteristics of non-linear and time-leg, we designed the fuzzy controller, through the adjustment of fuzzy rules on-line controled inverter's output frequency . Water supply systems collected outlet pressure every half hour through pressure transmitter installed in the water supply pipes, and then real-time collected the outlet flow through the flow transmitter, as the outlet flow and pressure have a linear relationship, so every flow value can calculate it's pressure ,take this pressure as PLC's setting pressure, compared with the actual pressure, calculated pressure difference and the shift rate of the pressure difference, then put them into the fuzzy controller to regulate the inverter's output frequency , and then control the speed of water pumps. When the PLC received the overflow frequency signals , it can carry through Variable Frequency Pump's logic switching timely. Compare with the traditional methods of water supply, the system has obvious energy saving effect and stability characteristics and broad application prospects. The system integrating with communication, networks, fuzzy control, computer, automation, remote control and many other advanced technologies, fully embodies the modern information technology and automation technology in the urban water supply systems.