Abstract : This paper introduces the design of a control system for a water supply pump set based on PLC and variable frequency speed regulation technology . The system composition, working principle, and fuzzy control strategy design are explained. This system effectively solves the problems of poor stability and difficult parameter adjustment in traditional PID control, improving water supply quality and achieving significant energy savings. It has practical and widespread application value. Keywords: PLC; frequency converter; fuzzy control; constant pressure water supply Keywords : PLC, Inverter, Fuzzy control, Water supplying Introduction With the development of variable frequency speed control technology and the increasing demands for drinking water quality, variable frequency constant pressure water supply systems have gradually replaced traditional constant speed pump switching pressurization systems, regulating valve water supply systems, and elevated water tower water supply systems. These systems are widely used in multi-story residential communities and high-rise buildings for domestic and fire-fighting water supply. However, water supply control systems that combine microcontrollers or PLCs with frequency converters often continue to use some old equipment from the original system (such as water pumps). In the practice of retrofitting existing water supply systems with frequency converters, some theoretically unexpected problems often arise. For example, microcontrollers are difficult to design in terms of hardware and software, and program debugging is challenging, resulting in poor system anti-interference performance. Using PLCs with diaphragm outputs, on the other hand, results in high equipment costs, difficult PID algorithm programming, and requires highly skilled debugging personnel. Therefore, for systems where the mathematical model is difficult to determine and the control precision requirements are not high, these systems may be less suitable. Combining PLC with AC variable frequency speed regulation technology and employing a practical and effective fuzzy control algorithm, the development of a constant pressure water supply fuzzy control system that is easier to adjust water supply parameters, has high reliability, and good control performance has high practical value. [b]1 Design of Variable Frequency Constant Pressure Water Supply Control System 1.1 System Design Scheme Analysis[/b] Currently, most water supply enterprises in China still use squirrel-cage asynchronous motors for the typical electrical drive of water pumps, because they have advantages such as simple structure, reliable operation, convenient maintenance, and low price. However, their speed regulation is difficult, so they often operate at a constant speed; when flow regulation is required, valve regulation is used, which wastes at least 20% of energy. Statistics show that water pumps consume more than 20% of the total electricity consumption in my country each year, and electricity consumption accounts for more than 60% of water costs. [b][align=center]For more details, please click: Application of PLC in Constant Pressure Water Supply Fuzzy Control System[/align][/b]