Research On High Gain DC/DC Converter Based On Coupled Inductance

With the development of science and technology,the use of direct current has become more common.In order to adapt to the changes in the global power consumption structure,the research and development of clean energy such as photovoltaics and fuel cells has become a hot topic in countries around the world.In view of the low output voltage levels of photovoltaics and fuel cells,research on high-gain DC converters with high efficiency,high power density and simple structure has become the focus of research in the new energy industry.Based on the analysis and summary of the boost technology of high-gain DC/DC converters,this thesis combines the advantages of various technologies and proposes a new type of coupled-inductance high-gain DC/DC converter(Fibonacci Switch Capacitor-Y Sources DC/DC Converter——FSCYS).The design of the converter is based on preset corresponding performance indicators in advance,and then by incorporating various boost technologies,the corresponding performance of the converter is gradually realized.Compared with similar converter topologies,FSCYS converters have the following advantages: 1.The input current is continuous,and no impact current will be generated to the subsequent stage at the moment of starting.2.The gain adjustment is flexible,the addition of three-coupled windings is equivalent to having three degrees of freedom to adjust the voltage gain.3.High boost factor.The expression of the converter boost factor contains fractions of different coupling winding turns ratios,and high voltage gain can be achieved by adjusting the turns ratio reasonably.4.The passive clamping circuit of the converter can not only absorb the leakage inductance energy,but also suppress the voltage spike on the switch tube.5.The number of components is small.Compared with other high-gain coupled inductor converters,the number of diodes and capacitors is relatively small.The thesis discusses the continuous conduction(CCM)state and discontinuous conduction(DCM)state of the FSCYS converter in detail,and derives the parameter conditions when the converter is operating in the critical conduction state(BCM).The boost factor of the circuit under ideal working conditions and the voltage and current stress of each component are calculated.The efficiency of the FSCYS converter under the influence of parasitic parameters is analyzed,and the parasitic parameters that have the greatest impact on the efficiency of the converter are analyzed through the control variable method.The influence of leakage inductance on the circuit boost factor and efficiency is analyzed,which provides a theoretical basis for the circuit parameter design of FSCYS converter.The thesis compares the PID and sliding mode control methods.In view of the complex modeling of PID control,poor dynamic response and weak robustness,it is difficult to adapt to the characteristics of high-order converters.The thesis decides to use sliding mode variable structure control to improve its shortcomings.Simulations and experiments show that the sliding mode variable structure control is very suitable for closed-loop control of high-order DC/DC converters due to its simple modeling method,ultra-fast dynamic response and strong robustness.The thesis uses Matlab/Simulink software to simulate and compare the dynamic performance of the two control methods under input voltage and load disturbances.Finally,the theoretical analysis of the proposed FSCYS converter was verified through experiments,and a 200 W experimental prototype was designed and built in a laboratory environment.The test results of the open-loop prototype verify the accuracy of the steady-state theoretical analysis,and the test results of the closed-loop prototype verify the feasibility of sliding mode variable structure control in the control of high-order DC/DC converters.