Research On Aircraft Secondary Power Supply Based On Hybrid Controlled LLC Resonant Converter

High-voltage DC(HVDC) aeronautical power 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 system in aeroplane. This dissertation is devoted to theoretical study and engineering practice on DC/DC converter of secondary power supply in HVDC power system. The Full-Bridge LLC resonant converter(FB-LLC) is very suitable for the DC/DC bus converter in HVDC power system, because it has the advantages of simple configuration, zero-voltage-switching(ZVS) for the switches and zero-current switching(ZCS) for the rectifier diodes in a wide load range.In the first section, the operation principle and the features of frequency controlled FB-LLC are discussed in detail. In addition, voltage gain distortion in light load condition caused by parasitic parameter is also analyzed. In order to solve the problems caused by gain distortion, a hybrid control method for FB-LLC is proposed.The operation principle and the features of hybrid controlled FB-LLC is analyzed based on time domain analysis and the relationship amaong voltage gain, frequency and duty ratio is derived. The output voltage is regulated by frequency control over entire load conditions. Moreover, basing on the loss analysis, an optimum duty ratio is predetermined to minimum the power loss at each load point in light load conditions.In order to reduce the loss of the rectifier in the low voltage and big current situation, the synchronous rectification(SR) technology is applied. The experimental resulat between magnetic inductance separation plan and SR drop voltage detection plan is compared. The SR drop voltage detection plan is finally determined to be the SR method in this thesis, and on this basis, an external inductor is used to compensate the duty ratio loss in SR driving signal.Finally, a prototype of 270V/28 V 1kW output is fabricated and tested in the lab, and the experimental results are provided to verify the effectiveness of the proposed converter.