Variable-Frequency Constant-Pressure Water Supply System Using Synchronous Switch With PLL

The paper proposes a design of constant pressure water supply using synchronous switch with phase-locked loop and Fuzzy-PID control.Two main problems exist in middle and large volume water supply system. First, because pipelines are so complex that controlled object is high order, delay, coupling, nolinear and time-varing, it is difficult to realize closed loop control for it using valid mathematic model. To resolve this problem, the paper presents a Fuzzy-PID control algorithm with self-adjusting regulation factor. Second, if a moving motor supplied by inverter power is switched to be supplied by power supply, the impact of overload-voltage and overload-current appears. PLL technique can be applied to avoid this impact and complete the smooth switch on condition that frequency and phase of inverter power and power supply are same.The paper primarily introduces the design of Fuzzy-PID controller for water pressure and phase-locked loop, and the design of software and hardware of 8031-based single-chip microcomputer control system. Moreover, it put forwards simulation results of the control algorithm and debugging results of the system over simulating water supply equipment At the end, it analyzes the control performance and existing problems of the system, as well as has some ideas on improvement.