Energy efficient control strategy for parallel variable-frequency pumps in the refrigeration system of an automobile factory

Abstract The operating power of parallel water pumps is influenced by their output head, flow and efficiency. Therefore, improving the operation efficiency of the water pumps is crucial for energy conservation while meeting output head and flow demands. This study aims to enhance the operating efficiency of pump units without changing their output. The parallel variable-frequency pumps in the refrigeration system of an automobile factory in Shanghai were selected as the research object. Firstly, the historical operating data was exported from the energy management system. The operating data was fitted by the least square method, and the actual performance model under different pump numbers and frequency combinations was established. Secondly, MATLAB was used to develop a mathematical model to traverse the working conditions, and the operating efficiency of all working conditions under different pump combinations was obtained. Then, the optimal number of pump combinations at each operating condition point was selected and the optimal number of pump partitions was obtained. The results showed that under the original operating mode, the number of pump combinations at many operating condition points was not optimal. Consequently, an optimized operating strategy was equationted based on the actual on-site situation. After deployment, this strategy resulted in an energy-saving rate of 7% for the water pumps. This study provides significant insights into improving the efficiency of pump units and demonstrates that operating costs can be reduced without hardware modifications.