Our smart variable-frequency constant-pressure water supply equipment adopts programmable logic controller (PLC) to collect the data of real-time pressure at the outlet of pipe network. The variable-frequency speed controller will regulate the rotation speed of water pump through PID calculation. Its main characteristics are adoption of advanced technologies, high degree of atomization, safe and reliable operation and easy management and maintenance which guarantee the intellectualization of the entire control system. Before the equipment is put into operation, the operation parameters i.e. working pressure of equipment shall be set first. During operation, the pressure sensor constantly collects the signals of water pressure of water supply network and change rate of water pressure, coverts them to electrical signals and sends them to the variable-frequency control system. The control system will perform comparison and calculation between the feedback signal and the set pressure. If the actual pressure is lower than set pressure, a command is issued to accelerate the speed of water pump. Otherwise, the speed of water pump will be lowered. When the actual pressure reaches the set pressure, the water pump will be maintained at current operation frequency. Where the water pump reaches the rated rotation speed (frequency), if the pipe network pressure is still lower than the set pressure after a certain period of judgment, the control system will maintain the normal operation of the water pump and change the frequency in order to start the next water pump until the pipe network reaches the set pressure. Otherwise, if water consumption of the system is reduced, the system will issue a command to reduce the operation speed of water pump. After it’s reduced to the valid rotation speed of water pump, the water pump which is first started among all water pumps in operation will stop running. In this way, the number of water pumps in operation is reduced until the pipe network pressure is constantly maintained within the set pressure. This system will perform real-time monitoring of the flow and pressure to achieve efficient and energy-saving operation.