| The high gain DC converter with low input voltage and high output voltage is always needed in power generation system used new energy like solar energy or fuel cell,uninterrupted power supply system and electric vehicles.The efficiency of conventional boost converter will reduce sharply when duty cycle exceeds the fixed value due to the equivalent series resistances of power devices and the stray parameter of the switch,so the conventional boost converter is just suit for the occasion where the needed voltage gain is less than four.Therefore,the research of DC/DC converters with high voltage gain and high efficiency has important significance.On the basis of previous study results,one non-isolated dual switches high step-up converter based on dual coupled-inductors is proposed firstly.The voltage-lift units of the proposed converter is built by taking advantage of coupled-inductor and switched-capacitor techniques,and the voltage gain is further extended by connecting two modules input parallel and output series.The first proposed converter has many other advantages in addition to high boost ability,such as low input current ripple,low voltage stress of power device,ZCS soft switching,the recycle of leakage inductance energy,and the restraint of the diode reverse-recovery problem.After that,two primary windings of the first proposed converter are merged together by introducing one three windings coupled-inductor,and the single switch is shared by two modules.So the other non-isolated single switch high voltage gain converter based on three-winding coupled-inductor is proposed.The volume and the number of the second proposed converter is reduced substantially although the ability to step up is decreased slightly,and it possesses other characteristics of the proposed converter based on dual coupled-inductors.The operating principle and steady-state performance of two proposed converters are analysed detailedly and verified preliminarily by Matlab/simulink simulation.The small-signal model is built by using the state-space average method,and the controller is designed taking the second proposed converter for instance.Finally,a 400 W prototype is constructed using TMS320F2812 DSP as the digital control core,and the validity of theoretical analysis is confirmed by experimental results. |
