Simulation And Optimization On Automatic Control In VAV Air Conditioning System

With the improvement of quality of life, the requirement of people for the comfort of central air conditioning system is higher and higher, so that the VAV air conditioning system is widely used. In VAV air conditioning system, whether the comfort requirement can be met and the energy can be saved or not depends on the automatic control system. In order to achieve the comfort and energy saving, the simulation and optimization have been done for total air volume control and pressure-independent VAV terminal control in this paper.Firstly, one air conditioning zone of an office building is chosen as an example,for the air conditioning zone, a VAV air conditioning system is designed, and the equipment selection for the total fan and the VAV terminal is done. The Flowmaster software is used to model and simulate the air conditioning system, through the simulation of the air conditioning system under PID total air volume control, simple total air volume control and correctional total air volume control, it is found that the PID total air volume control is not suitable for the control of total fan, and the control effect of the simple total air volume control and the correctional total air volume control are basically same, but the algorithm of the simple total air volume control is easy to realize, therefore, the simple total air volume control is an optimal scheme for the control of the total fan.Secondly, In order to achieve the temperature control requirement of the air conditioning zones, the mathematical models of the air conditioning temperature and the components of the VAV terminal are established in this paper, and a model closer to the actual condition is put forward. In addition, the VAV terminal control system is modeled and simulated by using the Matlab/Simulink software, and the PID parameters are optimized by the method of genetic algorithms. Furthermore,through the simulations of the VAV air conditioning system under the condition of the variable load, it's concluded that using the optimized PID parameters to control the indoor temperature can reach better control results.Finally, based on the premise that the total fan is controlled under the method of the simple total volume control, the methods of the VAV terminal control are studied. The study results show that only the VAV terminal fan is controlled, the primary flow rate will deviate from the set value, so the control strategy goes against the temperature control in time. When just the VAV terminal valve is controlled, under this condition, the terminal fan operates in constant frequency, and the indoor air temperaturecan achieve the control requirement, but this control method cannot save the energy.While under the simultaneous control of the VAV terminal valve and the VAV terminal fan, not only can the indoor air temperature meet the control requirement, but also the control strategy can save the energy.