建筑能耗在社会总能耗中占有很大比重。而空调系统的能耗比例超过了建筑总能耗的40%，在集中空调系统能耗中，水系统的能耗约占到整个空调系统能耗的60%~80%。水泵作为水系统输送设备中的重要组成部分，运行时的效率和能耗直接影响到整个系统的运行能耗。变流量空调系统可以依据负荷变化调整输配流量，降低机组和水泵能耗。本文对集中空调系统变频变流量控制时的节能性进行了分析和研究。 分析了集中空调变流量系统的原理、冷冻水系统变流量的类型及变频控制方式，得出在变流量系统的水泵变频控制方式中，根据负荷不断调整设定压差的变压差控制反应快，节能效果好。 分析得出了变流量集中空调系统变频水泵功耗的计算方法。对于变频水泵，若系统管网特性曲线为广义管网特性曲线时，变频前后工况点之间不满足泵或风机的相似律，变频后的效率应该由过新工作点的相似工况曲线与额定状况下水泵性能曲线的交点来确定；若系统管网特性曲线为狭义管网特性曲线，且当其管网特性（阻抗S）不变时，变频前后的工况点符合相似律，水泵能耗可用相似律进行计算，当变频的同时，管网特性也发生变化，则变频前后的工况点不满足相似律。 通过简化水系统分析比较了集中空调冷冻水系统变流量控制中阀门调节与定压差变频控制调节、定压差控制与定末端压差变频控制调节，以及定末端压差控制与变压差变频控制调节各自两者之间的节能效果。得出定压差控制水泵变频调节的节能效果优于阀门调节，定末端压差控制的节能效果优于定压差控制，变压差控制的节能效果优于定末端压差。从而得出：如果想要充分发挥水泵变频调节的优势，在控制调节过程中，一方面应尽量减少甚至避免调节阀上的能量损失，以保证管路特性相对稳定；另一方面在保证各个末端有足够的压差来保证其流量的前提下，控制系统压差设定值可变。对于集中空调采用变压差变频控制变流量系统节能效果最好。 最后结合西安市西北电力设计院集中空调系统的实测数据对其变频变流量一次泵水系统的节能性进行了分析。通过对该冷冻水系统分别采用定压差控制和变压差控制进行能耗计算并分析比较得出，采用变压差控制水泵变频的节能效果优于采用定压差控制。 变压差控制相对于定压差控制平均每小时可节电 12.35KW，全年可节电44645KW•h。按每度电0.65元计算，每年可节约29019元。折合成一次能源标准煤为16157kg。

Building energy consumption has been accounting for a large proportion of the total social energy consumption. The energy consumption of air conditioning systems has more than 40% of the total building energy consumption,and in the energy consumption of central air conditioning systems, the energy consumption of the water systems accounts for about 60% ~ 80%.The operation efficiency and energy consumption of the important part of the water system conveying equipments water pumps directly affect the whole system operation consumption. The VFV air conditioning system can adjust flow distribution in accordance with the load change,which can reduce the energy consumption of chillers and water pump.In this paper ,the energy saving performance of VFV air conditioning system using frequency conversion control was analysed and reseached. The principle of VFV air conditioning system, basic types of Variable chilled water flow system and the frequency conversion control methods were analysed. It is come to that, In the frequency conversion control methods of VFV systems,the variable pressure difference control method which can continuously adjust the set pressure difference according to the load has fast control response and energy-saving effect. The power consumption calculation method of the variable frequency pump was obtained through analysis.For the calculation of variable frequency pump power consumption, if the system pipeline characteristic curve is the generalized network characteristic curve, the similar condition curve of the new operating point should be first obtained,then the intersection of the water pump H-Q curve of the rated condition and the similar condition curve is just similar to the new operating point,thus the pump efficiency after frequency conversion can be determined,and the pump power consumption after the frequency conversion can be calculated based on the pump shaft power formula; If the system pipeline characteristic curve is the special pipeline characteristic curve, when the tube characteristics (impedance S) is constant,and the operating points of the pump operating in different speeds are similar operating points,the water pump power consumption can be calculated according to the similar law,and when the pump rotation speed is changed,and at the same time, the S value also changes,the operating conditions in different speeds are not similar condition,and the above relationships are not applied to it. Furthermore,the energy-saving effect of the valve regulation and the constant pressure difference control variable frequency regulation,the constant pressure difference regulation and the end constant pressure difference regulation,and the end constant pressure difference regulation and the variable pressure difference control frequency conversion when the central air-conditioning chilled water system operates in variable flow control were deep analysed and compared.It is come to that the energy-saving effect of the constant pressure difference control variable frequency regulation is superior to that of valve adjustment, the energy-saving effect of the end constant pressure difference regulation is better than that of the constant pressure difference regulation,and the energy-saving effect of the variable pressure difference regulation is better than that of the end constant pressure difference regulation.Thus it is drawn that,in the process of control regulation, on the one hand, the energy loss of regulating valve should be tried to be reduced or avoided and the pipeline characteristic should not be changed,on the other hand, under the premise of that each end has enough pressure difference to ensure the flow operation,the pressure difference setting value can be changed,so that the greatest advantages of variable frequency pump adjustment can pe played. Therefor,it is determined that when the air conditioning system uses the variable pressure difference regulation to control variable frequency pump to change the flow,the energy-saving effect of variable frequency pump can get the maximum embodiment. Finally,combined with the measured data, the energy-saving performance of a pump frequency conversion variable flow water system of Northwest Electric Power Design Institute in Xi’an was analysed. The energy consumption of the air conditioning chilled water system using the constant pressure difference regulation and variable pressure difference regulation to control the variable frequency pump was respectively calculated and compared.It is concluded that the energy-saving effect of this chilled water system using the variable pressure difference regulation to control the variable frequency pump is better than that of the constant pressure difference regulation.It is caculated that if this system use the variable pressure difference regulation, the average electricity-saving quantity is 12.35KW/h,and the annual electricity-saving quantity is 44645KW•h relative to the system operating in the control of the constant pressure difference regulation.If the price of electricity is 0.65 yuan/ KW•h,it can save 29019 yuan every year,which is equivalent to 16090 kg/y standard coal.