The Research Of Optimization For Ground-Coupled Heat Pump Control System

In recent decades, energy is the foundation for the development of the national economy. Ground-coupled heat pump (GCHP) is a kind of energy saving, high efficient and environmental protecting air conditioning system, which uses the renewable geothermal energy resources. As the environmental problems and energy crisis increase seriously currently, rational utilization of geothermal resources is one of the approaches which can solve these problems effectively, but how to make the energy-saving more effective has a practical meaning.In this paper, in order to change the phenomenon that nearly whole water pumps in the ground-coupled heat pump system work with fixed frequency and one of villas in Nanjing with this kind of heat pump system spent more than 2000 RMB on electricity per month, we study advanced control algorithms in ground-coupled heat pump system. The main contents are as follows:Firstly, as building a GCHP system costs too much, a laboratory-used small GCHP system is built which is used for research with some reasonable assumptions.Then, as speed control can save more energy than valve control in variable water volume (VWV) system, we try to make the speed of the water pump change due to the changes of the thermal loads. In many process control systems, cascade structure has a better control performance than single-loop structure, so cascade control method is proposed in this paper. After the control structure is determined, the models of flow loop and temperature-difference loop are identified by using the MATLAB system identification toolbox. The flow-loop’s model is mainly studied in this paper.Hereafter, the dynamic performances of the flow loop with different control algorithms are shown. As traditional PID control has three tuning parameters and its control effect cannot meet high demands in process control now, the PID control based on internal model control (IMC-PID) is proposed and it has a better dynamic quality in both matched and mismatched models.Due to GCHP system has strong disturbances, a feasible approach of disturbance rejection should be proposed for saving energy. An extended state observer (ESO) based control scheme is proposed. It can estimate the lumped disturbances and compensate them in the feedforward channel to improve the performance of the system. The simulation results show that the ESO-based control method can not only save the energy but also satisfy the demands for comfort.At last, the dynamic performances of the temperature-difference loop with traditional PID control and IMC-PID control algorithms are shown. The simulations results shows that the IMC-PID control has a better dynamic performance than the traditional PID control algorithm.