Study Of Energy-Saving Control System In Ground-Source Heat Pump Central Air-Conditioner

As humanity is now faced with energy and environmental problems, the exploit of new energy sources is imperative. Geothermal energy resource is winning people's high favor for its clean, non-polluting and renewable characteristics. Ground-source heat pump central air-conditioning system is a kind of air-conditioner which exploits shallow geothermal for both heating and cooling. There is a low degree of automation in the current ground-source heat pump air-conditioning system, and the control system has large energy consumption, resulting in low system efficiency. Thus, it is particularly essential to study a highly efficient and stable automatic control system to reduce the energy consumption of ground-source heat pump air-conditioner and improve the efficiency.The currently used ground-source heat pump control system has a low control precision. It can't well track the system load and especially does not have the adaptive capacity in the temperature control yet, which makes it difficult to meet the comfort and efficient energy-saving requirements. To solve the problem, in this paper the fuzzy control technology is introduced into the control of ground-source heat pump and combined with the traditional PID control algorithm, to design a set of frequency conversion fuzzy PID control system, so that it can get accurate temperature and flow control in the heating and cooling processes of ground-source heat pump, and improve the heat pump system operating efficiency and reduce maintenance costs.As the ground-source heat pump central air-conditioner is a nonlinear system which has a big lag and disturbance factors, the traditional PID control can not well meet the control requirements, while the fuzzy control does not require a precise mathematical model of the controlled object, making it an extensively applicable system. So the application of fuzzy control is reasonable in central air conditioning system. However, due to its relatively high precision, PID control is still a commonly used control technology. The combination of fuzzy control and PID control can take the advantages of both and avoid the inadequate.In the flow control of traditional central air-conditioner electric valve is a commonly used method, controlling water flow by increasing or decreasing the opening degree of the electric valves. Although this control method also allows the air-conditioning water system to adapt to the load changes, it wastes a lot of energy in the baffle of the valve and can not meet the energy conservation requirements. With the development of frequency conversion technology and the gradually deep application of inverter, in this article we take a controlling manner of frequency conversion on the pump to achieve stepless speed regulation in order to save power by using inverter to control the speed of pump.PLC (Programmable Logic Controller) is used as an on-site control device in the control system. With the temperature and pressure information of circulating water and indoor ends of ground-source heat pump system collected by multiple sensors, the fuzzy PID controller can make directive real-time control on the inverter. PLC is connected to the upper IPC through the fieldbus, to achieve centralized remote control of air-conditioning system and reduce operator's labor intensity.The ground source heat pump air conditioning variable flow temperature control system designed in this article is simulated in Matlab/Simulink, and the result shows that the adaptive fuzzy PID controller can obtain good control effect.The energy-saving temperature control system designed in this article incorporates modern advanced control technologies and concepts. It has practical value, and can promote further extensive using of ground-source heat pump central air-conditioner, thus has important guiding significance.