In this system, a D71 110KW frequency converter is used to drive a 110KW heat network circulating pump. By collecting the temperature difference between the total output and return water temperature of the system, and comparing the temperature difference of the user system return water temperature in each area with the system design temperature difference, the speed of the circulating pump is automatically adjusted by the built-in PID function of the inverter to realize the adjustment of the total flow and temperature of the system.