Optimal control of outdoor transmission and distribution pipe networks for district heating and cooling systems

Abstract

The optimization of the differential pressure setting value mostly uses the valve position signal as the monitoring parameter, but in the district heating and cooling systems (DHCSs), the end valve position signal has hysteresis and cannot be completely collected. Therefore, a variable differential pressure control strategy based on end-load monitoring is proposed in this paper, which can satisfy differential pressure requirements at the most unfavorable thermodynamic end. Then combined with the optimal control of parallel pumps, pay attention to the situation that the rated head of the variable frequency pump is much greater than the differential pressure of the pipe network, and consider operating at the lower frequency limit of the variable frequency range to minimize the total energy consumption of the pump. A district energy station in Chongqing is used as the research object to verify and evaluate the proposed optimization strategies. The test results reveal that the proposed optimal control strategies demonstrate a positive control effect and the performance of the pipe network and pump operation are significantly improved. Compared with the traditional constant differential pressure control strategy, the energy consumption of the pump under heating conditions can be reduced by up to 34.27%.