| High-voltage DC(HVDC)aeronautical power supply system has the advantages such as lower weight and easiness to realize uninterruptible power supply,which has been regarded as the future trend of the power supply system in aeroplane.This dissertation is devoted to study on the DC/DC converter of the secondary power supply in 270 V HVDC power supply system.The main research objective of this thesis is the control strategies of shorted-load current-limiting and paralleling current-sharing for two-stage and single-stage aviation DC/DC converter.For the two-stage aviation DC/DC converter,it consists of the front-end LLC DC transformer(LLC-DCX)and the back-end interleaved synchronous Buck converter,whose characteristic is that the shorted-load current-limiting and paralleling current-sharing can be realized easily by controlling the back-end Buck converter.An improved control method based on the output voltage feed-forward(OVFF)is proposed to suppress the current-overshoot under shorted load,which practically does not affect the performance of the original double-loop control system.The paralleling current-sharing control strategy of Buck converter is the three-loop control structure,in which the master-slave method is adopted within the module and the maximum current sharing method is adopted between the modules.For the single-stage aviation DC/DC converter,the structure is interleaved paralleling full-bridge LLC resonant converter(FB-LLC).The operation principle and voltage gain characteristics of the PS-PFM hybrid controlled FB-LLC are analyzed based on time-domain analysis,and the influence of phase-shifting control on the soft-switching performance of the converter is discussed.The current-sharing control strategy based on phase-shifting control is presented.Through the analysis that the influence of duty ratio on gain characteristics and efficiency,the optimal design method of resonant network parameters is elaborated.Finally,two prototypes of 3kW two-stage and 1kW single-stage aviation DC/DC converters are fabricated and tested respectively,and the experimental results are provided to verify the effectiveness of the proposed control strategies. |
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