Research On Quasi-Z-Source DC-DC Converter With Voltage-lift Cell

With the traditional energy shortage and environmental pollution becoming more and more serious in recent years,the renewable energy has got rapid development.The renewable energy grid-connected power system is usually required to converter the lower DC output voltage to higher DC voltage,so high step-up ratio DC-DC converters become one of the key technologies for renewable energy grid-connected access.Traditional Boost circuit is difficult to adapt to the new situation because of single structure,narrow output range,weak anti-interference ability and limited boost ability.In order to overcome the shortcomings of the traditional Boost converter and meet the requirement of the renewable energy power system,Professor Peng presented the Z-source converter,which has the characteristics of stable output voltage,high reliability and good economy.It becomes a hotspot in the field of renewable energy conversion in a short time.However,the Z-source converter has some disadvantages,such as discontinuous input current,high capacitor voltage stress and limited step-up ability.In order to improve the performance of the Z-source converter,the quasi-Z-source converters made some improvements,which can achieve continuous input current,reduced capacitor voltage stress and common ground between the input and output ports.However,the voltage gain is the same as Z-source converter.Therefore,various high-performance quasi-Z-source topologies have been proposed on the basis of the traditional Z-source and quasi-Z-source topology.But they are still insufficient in voltage gain,capacitor voltage stress and components number.The Z-source and quasi-Z-source topology have a wide range of application,and their application to DC-DC converter has unique advantages,such as simple topology,simple control strategy,strong anti-interference ability,high efficiency and so on.So they have good application prospects in the field of renewable energy power systems which need high step-up ratio DC-DC converters.This paper proposed new quasi-Z-source DC-DC converters with voltage-lift cell,which include two types of input current continuous and input current discontinuous,and the proposed quasi-Z-source DC-DC converters with voltage-lift cell are analyzed in detail.Compared with the conventional quasi-Z-source topology and its improved topologies,the proposed quasi-Z-source topologies with voltage-lift cell retain all the features of the conventional quasi-Z-source networks and have higher boost abilities,the lower capacitor voltage stress.Then the parameters of capacitors and inductors and the selection of diodes and the switch of the main circuit have been optimally designed.Finally,this paper makes the open-loop and closed-loop simulation by using Matlab/simulink simulation software,and then build a prototype for experimental verification in Lab.The experimental results agree well with the simulation results,and they both verify the accuracy of theoretical analysis and the effectiveness of the proposed converter.