| Nowadays Primary-secondary variable water volume system is the most popular air conditioning water system in large high-rise buildings or Multi-functional building groups. It can adapt to the changes of air-conditioner's consumer load under the real running situation and reduces the power consumption efficiently in cold water transport. However, because of universal labor control, the energy consumption and cost are high. This paper mainly deals with using pressure of supply and return main pipe in air-conditioning water system to better control rate of primary-secondary pump on line. The main contents are as follows:First, by analyzing the control methods of water system of VWV, we know that using constant pressure to control rate of primary-secondary pump has great energy-saving potential. Used laboratory of Intelligent building and Environment technical of Xi'an university of Architecture and technology as the research object, identifying pressure of supply and return main pipe and rate of transducer on line . This set up a foundation for the further research of water system's auto control and optimization.Second, I build a control system of central air conditioning based on LabVIEW. This system is composed of one main computer and three local computer. Main computer will monitor the whole system ,while local computer will undertake the optimizing control of local loop and transmit the real-time collected data to main computer through network. This system supply a good platform for the research of VAV central air conditioning energy-saving technique based on Large Scale System Optimization TheoryLast, I designed a Self-Tuning PID controller by using constant pressure control rate of transducer and use modified Ziegler-Nichols method to carry out PID setting. Running on-line PID control through identifying model on line and using MATLAB simulation, the result showed that the system ran stably and energy consumption was enormously reduced.
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