| In the new energy power generation system,the output voltage level of photovoltaic battery pack and fuel cell pack is low,the voltage fluctuation range is wide,and the stability is poor,which is not conducive to direct grid-connected transmission.In order to meet the requirements of bus voltage level on DC side of inverter,DC-DC converter is needed for DC boost conversion.Traditional Boost converter is limited by topology and parasitic parameters of circuit components,which makes the boost capacity limited,and it is obviously not suitable for use in photovoltaic and fuel cell boost field.The input current ripple of the converter will also affect the practical application effect of the converter.Excessive input current ripple will shorten the life of photovoltaic and fuel cell stack and affect the stability of the output voltage of the converter.Therefore,in this paper,four new converter topologies are proposed from the aspects of gain,efficiency and input current ripple,and related theoretical and experimental studies are carried out.The main contents are as follows:Firstly,this paper analyzes the current research status of DC-DC converters,and summarizes the characteristics,relations and limitations of different converters.To solve the problems of limited boost capacity and high voltage stress in the switch tube of the traditional quadratic DC-DC converter,a switch-coupled inductor quadratic high gain DC-DC converter is proposed.The simulation results show that the voltage gain of the converter is increased while the voltage stress of the switch tube is reduced after the introduction of the switch inductor and coupled inductor boost unit,and the larger voltage gain output is achieved with a smaller duty cycle.Passive leakage inductance absorption loop is introduced,which can effectively suppress the voltage spikes at both ends of the switching device and recover the leakage inductance energy to improve the working efficiency of the converter.On the basis of soft-switching topology,combining flyback boost unit and switched capacitor unit,a high-gain DC-DC converter with soft-switching coupling inductance is proposed.The experimental results show that the converter realizes ZVS turn-on of the switch tube and ZCS turn-off of the diode,which avoids the problem of excessive current spike at the moment when the switch tube is turned on and reduces the switching loss.The flyback unit and switched capacitor unit further improve the gain of the converter.Due to the influence of the primary side of the converter coupled inductor unit,the input current ripple is large.In order to reduce the input current ripple and reconstruct the converter topology,a low input current ripple soft-switching coupled inductor high-gain DC-DC converter is proposed.In this converter,the coupling inductor unit is placed at the back stage of the converter,which can not only retain the boosting ability of the coupling inductor,but also make the input inductor independent.The experimental results show that the input current ripple of the independent input inductor is much smaller than the primary leakage current ripple of the coupled inductor.The converter structure is beneficial to reduce the input current ripple,and realizes that the switch tube ZVS is turned on and the diode ZCS is turned off.Independent input inductor structure is beneficial to reduce input current ripple,but its effect is limited.Therefore,a passive current ripple injection unit is introduced,and a zero input current ripple soft-switching coupled inductor high-gain DC-DC converter is proposed.The experimental results show that the converter achieves approximately zero input current ripple while retaining the advantages of the original topology.Figure[72]table[5]reference[116]... |
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