Research And Application Of High Frequency Conversion Constant Pressure Water-Supply System

In the ear of gradually short of water and electricity resource,“save water and energy”has become an important theme to build a sustainable society. For a long time, the technologyof water supply in municipal high-rise buildings and factories etc. has been relativelybackward. The degree of automation stays a low level. Due to inadequate water supply,people cannot obtain a normal life and production, and even the fire disaster can cause aneconomic loss of230billion RMB per year. Therefore, to develop a stable and reliable,energy efficient and comfortable system of water supply has its significance. This thesis goeson a theoretical and experimental research of the speedgoverning mechanism and controlmechanism for high efficient frequency conversion constant pressure water supply system,enhances the frequency conversion control technology. The main work and the results are asfollows:First of all, according to the pipe network and pump operating characteristics curve, thisthesis clarify the frequency control energy-saving principle of the water supply system basedon the theory of variable speed control and AC induction motor principle. It has a comparativeanalysis of the characteristics of speed control mode for a variety of AC induction motor, andverify the rationality and reliability of the frequency control with the combination of the testdata in the related literature. Based on these results, it calculates and checks the inverter’smost important load parameters. Furthermore, it sets up the theoretical and mathematicalmodel of frequency conversion constant pressure water supply based on PID control theory. Itinvestigates the control strategy of frequency conversion constant pressure water supplysystem，and summarizes the practical control scheme. The results show that, general-purposeinverters+PLC+man-machine interface+pressure sensor is a reasonable controlscheme. Then describes the various components of the system and its roles. According to theprogram chosen, this paper designs for the constant pressure control program graph, theconstant pressure program in figure and motor of change control procedure diagram, and programs of the PLC with the application of the S7-200software. There are main program,subroutines and interrupt routines. Moreover, based on the theory of Fuzzy-PID, it designs theself-adaptive PID fuzzy control, and establishes the fuzzy rule table and membership functionwith MATLAB software，and obtains the step response curve and self-tuning curves. Theconcludes of the simulation: system adjustment time is short, and rapidly to reach stable. Thetone is smaller than the general PID control. Although exists dynamic overshoot, it is verysmall. Finally, it runs the system under the completion of the prototype water supply system,and records the test data. The results show that: pump power consumption and its speedproportional to the three power. The constant pressure water supply pressure can be stabilizedat around the setting range, which achieves the desired goals. It verifies through practice thefeasibility and advanced of frequency control and PID Control together to form a closed loopcontrol system during the real production practices.The achievement of this paper provides the basis for the domestic manufacturingvariable frequency constant pressure water supply system, and can be used to guide frequencyconstant pressure water supply system product. The work has important theoreticalsignificance and application value.