Study On Magnetically Intergrated DC/DC Converter With High-gain And Low Current Ripple

Fuel cells can convert chemical energy into electrical energy directly.Because of the clean emissions,fuel cells and the associated converter technologies are receiving more and more attention.However,the characteristics of fuel cells impose stringent requirements on the design of converters.This dissertation focuses on the related technologies of non-isolated high-gain DC/DC converters for automotive fuel cell applications.The converters for this project have four characteristics:the capability of high gain capability,wide range,low input current ripple,and non-isolated topology.The first chapter of this dissertation conducts literature research from two aspects for the aforementioned.charaterristics.The advantages and disadvantages of several existing topologies for this topic were analyzed.In the second chapter of this dissertation,a magnetically integrated high-gain,low-ripple DC/DC boost topology is proposed,which resolves the conflict between high gain capability and low input current ripple.The time-domain analysis of the proposed topology was conducted.The voltage gain formula with parasitic parameters was derived.The operation of each mode was analyzed.The parameters of the magnetic element that could achieve zero ripple were proposed.The effect of parameters deviation on input current ripple was analyzed.In the third chapter of this dissertation,two prototypes was designed and built for control experiment purpose.The parameters of the process and device selection results were given.The efficiency calculation was conduted combined with the selection results of the converter.A method of changing the coupling coefficient by adjusting the relative position of the winding and the number of turns of the coil is proposed.The measured values of the six parameters of the magnetic elements meet the design requirements.The small-signal model derivation and correction were performed for the two prototypes designed.To prove the validity of the derived model,the results of simiulation and sweeps of the prototype are compared.A method of double-pole double-pole compensation using a single-zero-point double-pole compensation device in series RC filter is proposed,which realizes closed-loop control of the input current.Input current sampling and protection circuits have been designed.The input current signal is obtained using a Hall current sensor,which achieves signal and power isolation.The output signal of the Hall element is removed by a differential amplifier circuit and the signal swing is amplified.The protection function is realized by the way of comparator output low-level lock switch,which can reduce the loss caused by fault conditions.In the fifth chapter of this dissertation,the simulation and experimental tests of two prototypes are conducted.The operation data of the two prototypes are recorded under more than ten kinds of input conditions.The experimental results show that the proposed magnetically integrated high-gain low-ripple DC/DC converter is superior to the control scheme in terms of ripple content,and is slightly better than the control scheme in terms of efficiency.The test result meet the technical requirements.