| The industry of refrigeration consumes great amount of energy in China today. The energy is mainly consumed by compressor, whose control effect is not good enough in the manner of energy optimization. So, there is much work to do in compressor control, for the purpose of economization.This thesis is to design a controller for large scale refrigeration compressors. A series ofstudy work is done around this point.Firstly, a new and more complete model based on an existing mode for small scale vapor compression cycle is set up, in which two water cycles for heat exchange are added, and the model is used to describe the large scale vapor compression cycles. Because of the difficulties in applying the model in reality, a simplified model is set up by reducing the numbers of over many parameters in the bound of a limited error. The two models are contrasted at some work points to test the validity of the simplified model.Secondly, a unisonous control strategy used to combine compressor speed and valve opening is explored. By this means, the system is always tracking the steady work point, which is benefit for the system control. A PID controller and a fuzzy controller are used to control the two cycles of evaporation pressure and superheat temperature respectively, aiming to satisfy the demands of both refrigerating capacity and efficiency. To validate the controller, some simulations are implemented on evaporating pressure and valve opening cycles, and the results show that the both controllers with tracking control strategy can make the system response more quickly and smoothly, with an inhibiting ability of disturbance brought by freeze water pump and condensation water pump.Finally, the both controllers are implemented on an embedded system. ARM7-TDMI series MPU S3C44B0X is used, as well as the real-time operating systemμc/os-Ⅱ, the applications are scheduled to accomplish the control functions.
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