Study And Simulation On Self-adaptive Static Pressure Variable Frequency Control In Variable Air Volume System

Driven by the energy-saving, variable air volume air is proposed at the historic moment. According to external load change, it can change the supply air in real-time to eliminate residual heat and humidity of the air-conditioning room. Compared with constant air volume system, it is of significant energy-saving effect. Variable air volume system control air volume by the adjustment of the fan system according to the change of static pressure, making the total air flow can match the demand air flow of terminal device adjusting, and keep the static pressure in the pipeline in a certain range.Before the development of frequency conversion technology, fan r egulation is realized through the method of changing the guide vane angle, damper and bypass air volume adjustment etc. With the development of frequency converter technology and the decreasing of price, fan speed control by the inverter has been widely applied in the Variable air volume system, with a significant energy saving effect.The control strategy of the total supply air volume of the variable air volume system includes constant pressure control and variable static pressure control. Constant static pressure control is commonly applied in the traditional variable air volume system. When the system load is reduced, the open degree of the valves of terminal device will be reduced to reduce the supply air volume, in order to meet the requirements of the indoor air volume. At this time, the static pressure will rise. Although the system static pressure can remain unchanged by reducing the fan speed, the decreasing of valve open degree will increase the system resistance, with the part energy of fan wasted in increase of resistance. Therefore static pressure control can’t reduce the energy consumption at the maximum degree. The variable static pressure control method can reset the static pressure value, so that the valve opening position as far as possible remain the largest, to reduce system resistance and the energy consumption of the fan.Given the problem caused by the control method of variable static pressure widely used now, which tends to cause overcooling or overheating in certain areas, self-adaptive static variable frequency control method is proposed. Unlike the conventional method, the self-adaptive control method tends to take into account the difference between the sum flow rates measured and required as well as the number of fully-open dampers to reset static pressure in order to maximally save energy and improve the indoor thermal comfort.In order to analyze the energy-saving situation of self-adaptive static variable frequency control method, simulation software Simulink is carried out to build the system model in this article. Self-adaptive static variable frequency control method is compared with the constant pressure control method. The simulation results show that the overall speed of the fan of self-adaptive static variable frequency con trol method is much lower than that of the static pressure control, that is to say, it h as obvious energy saving effect,and the energy-saving ratio is 9.91%.Self-adaptive static variable frequency control method is applied in to the VAV system of actual buildings, which can save the energy consumption of AHU fan efficiently compared with the static pressure control.