Research On Multi-output Converter Applied To Power System Of Spacecraft

Multi-output converters are widely used in spacecraft power supplies and other multi-electric systems that require multiple voltage levels due to their small size and low cost.When the load equipment have high requirements on their power supply quality,the traditional multi-output regulation methods based on the semicontrol methods are difficult to ensure that each output has good steady-state and dynamic performance.However,there are also shortcomings such as the limited application and complicated control for the multi-output regulation methods based on the full control methods.So the multiple output converter used in the spacecraft power system is studied in this dissertation.An accurate model of the half-bridge multi-output converter based on the cross-regulation of the transformer is established,which considers the parasitic parameters of the secondary side.The accurate expression of each output voltage,and the changing rules of cross-adjustment rate are summarized in the time domain analysis.The influence of cross-adjustment method on the cross-impedance and anti-input power disturbance of the multi-output system are analyzed in the frequency domain analysis.A new multi-output converter topology based on transformer secondary side control is proposed by summarizing and analyzing the causes of the output voltage coupling of the cross-regulated multi-output half-bridge converter.The primary side switches of the converter operate in a fixed duty cycle mode,and the output of each secondary side is controlled independently,which greatly reduces the degree of mutual coupling of each output.The energy of the primary side leakage inductance is used to achieve the soft-switching of the primary side switches,and the efficiency of the converter is improved under the premise of ensuring accurate voltage regulation of each output at the same time.The expression of the output voltage gain is derived by analyzing the working state of the new multi-output converter at different stages,which proves the feasibility of the scheme of accurate voltage regulation of each output.The statespace averaging method is used to complete the small signal analysis of the system,and the type III compensation network is used to complete the closed loop design of the system,which improves the steady-state and dynamic performance of the system.The frequency domain analysis of the system is completed by using SIMPLIS software at the same time,and the simulation results prove the correctness of the theoretical analysis.A simulation model and an experimental prototype of a two-output converter are built based on the results of theoretical analysis and parameter calculation.The steady-state results show that each output voltage can be controlled independently,and the output voltage and inductor current can meet the design specifications.The primary switches can achieve zero-voltage-switch.The dynamic results verify that the system can respond to the changes of input power and load quickly,and has good anti-disturbance performance.