Dong Qiaoxue

Frequency reformation of ground source heat pump system based on proportional control with grey prediction

Ground Source Heat Pump (GSHP) air conditioning system has been maturely applied in greenhouse temperature adjustment, which is mainly used for heating in greenhouse during the winter. Although GSHP system is a high-efficiency and energy-saving system, it still has the potential to save energy in the practical application by changing operation mode. The method of changing circulating pumps working frequency of GSHP system was proposed in the article. The greenhouse environment characteristics are a combination of great inertia, pure time-delay, nonlinear and model uncertainty which make it difficult for us to obtain an accurate mathematical model. Therefore, it is not advisable applying some traditional algorithms like PID control algorithm in the system. To solve the problem, this article introduces grey prediction method into temperature modeling process which uses previous temperature data sequence to forecast future temperature and the predicted future data as feedback value into the controller. The controller choose proportional control algorithm that uses the difference between the predicted temperature and the setting temperature to adjust the frequency of the circulating pump. In that way, the energy consumption can be reduced. To find the most proper proportional parameter, optimal control method is selected. Experimental results show that this control method not only improves the control quality of the circulating pump, but also achieves the purpose of saving energy.