Abstract
As every profession and trade of our country is being developed constantly, the energy
question is outstanding day by day in our country, and unable to solve at all in the near future,
the energy conservation is quite arduous. In such environments as the enterprise, office block,
commercial building, hotel of modern factory, etc, the central air conditioner system is
dispensable, though it can provide a comfortable environment for people, but the power
consumption is quite large. So paying attention to environmental protection and energy-
conserving today day by day people, energy-conserving problem of the central air conditioner is
a key technology problem to solve.
Besides dissipation energy of the host computer, central air conditioner system also has the
second largest consume energy equipment, such as air blower, freeze and cool water pump.
Based on the large flow of summer, the disposition of air blower, freeze and cool water pump
are determined (sets the margin on this basis). Because of the climate situation while using
actually, such changes of different factors as objective flow activity content, etc. Constant
change of necessary load (load seldom reaches the maximum). In order to make the systematic
temperature of central air conditioner steady, the air blower, freeze and cool water pump are
changed by working condition, this needs better automatically controlled module.
This paper explained some basic ideas and methods that the systematic automation on the
automation control and energy-conservation of central air conditioner and recommended the
characteristic and energy-conserving principle of VVVF on alternator. It also recommended
Siemens S7-200 main functional module and application and the application of PID algorithm
in VVVF. The paper made a detailed instruction to the main circuit and the hardware of control
circuit. This subject detected the export temperature of air conditioner, adopt the frequency
converter to regulate the rotational speed, and make it run high-efficiently and achieve the goal
of energy-conserving.
The whole system uses the modular design, the CPU module uses CPU226, the simulation
quantity expansion module uses EM231, may according to need to dispose various modules
quantity nimbly. Completes the parameter establishment and the control request through the
software design which the central air conditioning needs. The system software consists of the
master routine, the initialization routine and the analog quantity examination procedure.
Through calling the subroutine, the system completes the data acquisition, the examine of
analog quantity and the functions of audible and visual alarm.
Key Words：Central Air-condition；Variable Frequency Regulating Speed；PLC；PID
