The Design And Analysis Of Variable-Frequency Constant-Pressure Water-Supply System

The thesis proposes the unique properties of water-supply inverter which is special to the ordinary in constant-lever water-supply system. Based on Analysis of energy consumption, draw a conclusion that Energy-saving applied only in specific situations when using water-supply frequency inverter.Two main problems exit in the large volume water supply system .First, because pip- -elines are so complex that controlled object is high order, delay, coupling, nonlinear and time-varying, it is difficult to realize closed loop control for it using valid mathematic mo- -del. To resolve this problem, the thesis present the derivation of approximate model based on treating inverter and pumps as a whole part. For the particularities of controlled model, to chose the appropriate control method is very necessary. This thesis presents the simulat- -or in Matlab of fuzzy control and Ziegler-Nichols PID control. The simulator waveform indicates that Fuzzy control is better than PID control when the controlled object is uncer- -tainty.Second, if a moving motor supplied by inverter power is switched to be supplied by power supply, the impact of overload-current will appears because the voltage phase of inverter and power supply is asynchronous. The thesis presents a method of phase sync- -hronization by differing from frequency of inverter and power supply. With advanced el- -ectrical simulator software which is Saberdesigner, I complete analysis and design of the switch circuit. The result shows the proposed switch method is fast, simple, safe, reliable and practical.