Design On Drive And Control System Of Stirling Refrigerator With High Power Factor

As an important branch of the cryogenic technology,the Stirling refrigeration technology is widely used in fields of the aerospace,military,superconducting and cryogenic electronics,etc.Compared with the traditional vapor compression refrigeration system,the Stirling refrigeration system proves more promising in energy saving and environmental protection due to its advantages of the pollution-free refrigerant,the wider refrigeration temperature range and the higher efficiency.The linear Free-Piston Stirling Cooler(FPSC)has attracted more and more attention on account of the compact structure,light weight,low noise,small abrasion,high reliability and long life.However,the research on controllers of FPSC with the large refrigerating capacity is still in the initial stage because of the high technology and production cost.In addition,with the gradual increase requirements for the power grid quality,the active power factor correction(APFC)technology,as an effective measure of harmonic suppression,has been increasingly researched and applied in motor control.In this thesis,firstly,the research status of the Stirling refrigerator and its control system is introduced as well as the related techniques of the PFC and the temperature process control.According to the actual control demands,a single-phase linear FPSC control system is established based on the dsPIC30F4011 core control chip.The hardware and software design process are specifically elaborated.The hardware system includes the main inverter circuit,the signal sampling and modulating circuit,the serial communication circuit and the auxiliary switching mode power supply,etc.The software design comprises the main program structure,the software realization of the SPWM,the optimization method of the AD sampling,the soft start and the slow shut-down of the motor and the host computer programs,etc.Secondly,the control equation of the One-Cycle Control stratagy is deduced in detail based on the APFC principle.An APFC converter with the 400 V DC voltage output and the 1kW maximum power is designed based on IR1155.The design process of the power circuit and control circuit are concretely explained,among which the design of the high-frequency power inductor is emphasized.Thirdly,after the analysis of the fundamentals of the conventional PID control,the Stirling refrigerating process model is approximated by the first-order inertial time-delay transfer function,based upon which the MATLAB simulations are performed.The defects of the conventional PID method are detailedly summarized when it is applied in complex processes with the large inertia and long delay.Furtherly,the fuzzy control is introduced and combined with the common PID in order to improve the control effects.The parameter self-tuning fuzzy PID temperature control is developed.The design process is described at length.The software implementation is illustrated.The effectiveness is also verified by simulation.Finally,a single-phase linear FPSC experimental platform is built up to conduct the experimental study.Experiments include tests of the steady-state and dynamic performance of the power factor corrector,the performance of the inverters and the auxiliary power supplies and the temperature control effects.The results demonstrate that the optimized temperature control method possesses good static and dynamic property.The validity and reliability of the designed control system are proved to be qualified.