| With the rapid development of high-power ionic-electric propulsion technology in China,the power level of power processing unit(PPU)of ion propulsion has been continuously improved.High efficiency and high power density beam supply has become the development goal of PPU.As the core component of PPU,the beam supply has the best efficiency and stable output in the full power range,which is the key to achieve high efficiency and high power density of PPU.Therefore,in order to satisfy the requirements of multi-working condition,multi-mode and high-efficiency operation of the beam supply,a dual-mode mixed output switching strategy combining the phase-shifting/pulse-width dual-mode modulation technology with the series-parallel operation of the secondary side is proposed to optimize the efficiency of the system within the full power range.Aiming at the problems of low precision and poor anti-interference performance of traditional PID double closed-loop control,a double closed-loop control strategy with PID controller in the current inner loop and model predictive control(MPC)in the voltage outer loop is proposed to improve the anti-interference performance of the system.This thesis focuses on the technical requirements of wide range output voltage regulation under the condition of wide range input voltage of the beam supply of spacecraft propulsion system,and carries out the analysis and research of a new dual full bridge converter.A dual-mode mixed output switching strategy and a model-predicted dual closed-loop control strategy are designed from the aspects of the topology selection of the converter,working principle analysis,parameter calculation,etc.The main contents of the thesis are as follows:(1)Firstly,the application background of the beam supply for the spacecraft propulsion system is analyzed,and a topology is designed by comparing the development of the beam supply at home and abroad,which satisfies the condition that there is the wide range of output voltage regulation when the large-capacity beam supply under the wide-range input voltage condition.Secondly,the working status of the topology from series mode to parallel mode is analyzed,and the device parameters of circuit is calculated according to the technical indicators of the beam supply.(2)For the problem of further improve the working efficiency of the beam supply,a dual-mode hybrid output switching control strategy is proposed.By comparing the differences between the phase-shifting control and duty cycle control and the new dual full bridge topology,the power losses of the two control modes are calculated respectively,and then the output efficiency comparison curves of the two control modes are obtained.It can be seen from the comparison that the duty cycle control has the high efficiency under light load condition,and the phase-shifting control has the high efficiency under heavy load condition.Combined with the advantages of the two control modes and the two operation modes,four operation modes of phase-shifting series operation mode,phase-shifting parallel operation mode,duty cycle series operation mode and duty cycle parallel operation mode are obtained.And the two-mode hybrid output switching of the beam supply is realized and the efficiency of the system within the full power range is optimized.(3)For the problem of low precision and weak robustness of traditional PID control,a double closed-loop control method in which the current inner loop adopts the PID controller and the voltage outer loop adopts the MPC controller is proposed.This method takes the transfer function of output current and duty cycle as the controlled object to design the inner loop controller,and uses the inner loop as the controlled object of the outer loop to derive the outer loop model predictive controller.In order to verify the responsiveness of MPC double closed-loop control,the power circuit,traditional PID double closed-loop control circuit and MPC double closed-loop control circuit are built in MATLAB/SIMULINK,respectively.The performance of the two control methods is compared under four working conditions of sudden load reduction,sudden load addition,sudden decrease and sudden addition.Besides,the beam supply test prototype platform is built to further verify the response capability of dual-mode mixed output switching and model prediction dual closed-loop control through operating conditions such as sudden load reduction,sudden load addition,sudden decrease,sudden addition and dual-mode switching. |
