The Design Of Intelligent Frequency Conversion Control System On The Central Air Conditioning

With the rapid development of our country, all kinds of large buildings have mushroomed in every street. These buildings are becoming the main places for people to live, work and leisure, and the proportion of these buildings energy consumption in total energy consumption of the whole society is obviously rising. According to a survey, it showed that the central air conditioning system energy consumption proportion can amount to50%or60%in the commercial building energy consumption. Now more and more residential areas are using central air conditioning technology. So, in the circumstance of the current strained electricity supply, the rising price of power, energy conservation and emission reduction, protecting the environment, how to improve the efficiency of the central air conditioning system, reduce energy consumption and reduce running cost become a problem that we need to face.According to statistics, in the most cases the central air conditioning system has fluctuation operation with70%load and the air conditioning loads are changing at the actual operation. So the energy saving technology with frequency conversion will be widely applied in the control system of the central air conditioning. According to this way of thinking, This paper first analyzes the workings of the central air conditioning circulating water system and its inertia, hysteresis and non-linear. So it is difficult to establish the accurate mathematical model. For this reason, this paper proposed a method using fuzzy control theory to turn PID controller parameters, to control the central air conditioning circulating water system. And it also gave the design method for fuzzy PID controller. Finally we simulated it with MATLAB, the results show that this fuzzy PID controller is better than the traditional PID controller to control the temperature of the central air conditioning cooling water. This paper also gave a detailed introduction about the hardware and the software of the central air conditioning temperature control system. This control system took the S7-200PLC as core controller. Using fuzzy PID control algorithm, the motor speed of air conditioning pumps were controlled by Siemens MM440transducer, and we can achieve the purpose of frequency conversion and energy saving.