Modeling And Control Of DC-DC Converter For Fuel Cell Vehicle

A great increase in the number of fuel cars will not only consume oil resources,but also cause serious environmental pollution problems.The development of new energy automobile industry provides new ideas for solving these problems.Fuel cell vehicle has become a promising development direction due to its advantages of zero emission,no pollution and high efficiency.However,the low output voltage of the fuel cell makes it difficult to drive the electrical load directly.Moreover,the fuel cell has a "soft" output voltage characteristic.As the output current increases,the output voltage drops too fast and the output voltage range is wide.Therefore,it is of great significance to develop a fuel cell vehicle DC-DC converter with high-gain,wide input voltage range and small size.In this dissertation,some problems of DC-DC converter are firstly analyzed and a non-isolated DC-DC converter named SC-SL-Boost is proposed.The converter has some advantages such as high-gain,wide input voltage range and low voltage stress.There is a common ground structure between the input and output ports.All the power switches only need one drive signal.Besides,the topology can be extended according to the gain requirements.Secondly,the operation principles of the proposed converter are analyzed and the calculation equations for the voltage gain and the device stresses are derived.The extension structure of the converter is given and the converter is compared with some existing DC-DC converters for fuel cell vehicles.Then,the design processes of the device parameters are given.The state-space averaging method and small signal method are adopted to model the converter in order to complete the design of compensation network.Finally,a Psim simulation model is built to verify the effectiveness of the converter and an experimental prototype with rated power of 100 W is designed for experimental verification.The hardware and software of the experimental prototype are designed.The hardware circuits and program design flow are given.The main controller adopts DSP28335 and the control strategy adopts PI control.The rated input voltage of the prototype is from 25 V to 80 V,the rated output voltage is 200 V and the maximum efficiency can reach 93.1% in the rated state.The simulation and experimental results are consistent with the theoretical calculation results,which verifies the rationality of the proposed converter.The proposed SC-SL-Boost converter is suitable for fuel cell vehicles.