"节能型中央空调温度控制系统的PLC设计与应用--毕业设计"。

Central air conditioning systems are commonly used in both commercial and residential buildings to maintain a constant temperature throughout the entire structure. Traditional designs often result in significant energy wastage as motors run at full speed regardless of seasonal changes, day-night fluctuations, and varying user loads. This design project focuses on the integration of frequency converters, PLCs, temperature sensors, and other devices to create a closed-loop temperature control system that automatically adjusts the output flow of water pumps to achieve energy efficiency. The system utilizes Siemens S7-200 PLC as the main control unit and employs traditional PID control algorithms to regulate the speed of water pumps using Siemens MM440 frequency converters. This ensures that the system adjusts flow rates based on actual load conditions to achieve temperature control and minimize energy wastage. By incorporating a network based on the USS protocol and RS-485 bus communication, along with Siemens TD200 text display for human-machine interface design and MCGS industrial control software for system configuration, the design allows for theoretical analysis and verification of its reliability in addressing energy wastage in central air conditioning systems. Through the implementation of this design, the reliability and effectiveness of the system in mitigating energy wastage in central air conditioning systems have been validated. This project not only demonstrates the potential to solve energy wastage issues but also sets a precedent for future implementations of energy-efficient control systems in HVAC applications. Keywords: central air conditioning, PLC, PID, frequency converter.