The water ring vacuum pump can use the exhaustive method to obtain the optimal operating state parameters of the parallel pump that meet the conditions through numerical simulation. Under the design condition of the pipe network impedance S, the water ring vacuum pump is given a certain pressure difference set value, and all the speed combinations of the two parallel pumps that meet the pressure difference set value are solved, and then the corresponding speed combinations of each group are obtained. The total power of the pump is obtained, and finally the group of speed combinations with the smallest total power is found, that is, the optimal speed combination of the pump that meets the conditions. Further, the optimal speed ratio and the distribution of similar operating points can be obtained. Under a given pipe network impedance S, when different pressure differential set value requirements are met, the optimal speed ratio of the parallel pumps is a certain value, which is the same as the optimal speed ratio calculated by using criterion 3; The operating points remain unchanged, which are the same as the optimally allocated similar operating points calculated using criterion 2; the working efficiency of the water pump remains unchanged. Multiplying by a safety factor greater than 1 will result in a larger selection of the pump.
Therefore, the above-mentioned conditions rarely occur in actual conditions. If such a working condition occurs, the current inverter can realize over-frequency operation, that is, the output frequency of the inverter is greater than the power frequency 50Hz, but the bearing capacity of the pump motor must be considered. In addition, if conditions do not allow, in the face of this unusual working condition, priority should be given to ensuring the system's requirements, and it may not operate according to the optimal speed scheme. Aiming at the optimal control of the rotational speed of the parallel variable frequency water pump in the closed circulating water system, a characteristic model of the parallel variable frequency water pump is established. Through theoretical analysis, the optimal control criterion for the rotational speed of the parallel variable frequency water pump is summarized. The total cooling capacity of the building is recorded in the BMS. The historical operation data of the building air conditioning system is calculated hourly. The historical operation data includes the total water supply temperature of the building air conditioning cold water, the total return water temperature of the building air conditioning cold water, and the total water supply flow of the building air conditioning cold water.