Research On Topology And Construction Of High Gain Impedance Source Converters Based On Z-Network And Switched-Boost Network

With the development of renewable energy power generation technology,the highperformance high voltage-gain converter topologies,which are suitable for the new energy grid-connected power generation systems,such as fuel cells and solar energy,has become an important research hotspot in the field of power electronics technology.The impedance source converter,since it was proposed in the early 21 st century,has received extensive attention in the field of power electronic converter topology construction,which mainly benefits from its simple structure,single-stage buck-boost characteristics,can reduce the power conversion stage of the entire converter system and improve system performance.Based on this,the traditional Z-source impedance network and the switched-boost impedance network are taken as the research core main line of this thesis.According to their internal structural features,by changing the way connections between components,and combining with the structural characteristics of traditional boost networks such as switched capacitors and switching inductors.A hybrid impedance source network construction and derivation method is proposed.By applying these new constructed impedance source networks into the DC-DC and DC-AC power conversion fields.A series of high gain and high performance impedance source converter topologies are obtained,which further enriching the application of impedance source networks.The contributions of this thesis are shown in the following aspects:(1)In order to reveal the inherent mechanism that the impedance source network have the voltage boost capability.The detailed operating principles of these four basic impedance source networks(Z-source network,quasi-Z-source network,switched-boost network,quasiswitched-boost network)will be analyzed firstly.And the performance comparison among these four networks have been made.Their features,respective advantages and disadvantages,are also summarized,which aims to provide the construction directions for the new impedance source networks and the new high boost impedance-source converter topologies.(2)Based on the internal structure characteristics of the traditional quasi-Z-source network and the quasi-switched-boost network.By using an additional switched-capacitor branch combined with another switched-capacitor branch,which ishidden in these two basic networks,to form an integral switched-capacitor cell.Then,three high boost DC-DC converters with single switched-capacitor branch will be constructed,which further increases the output voltage gain and reduces the voltage stresses of power switches and capacitors.(3)By changing the connection ways of diodes and capacitors in the traditional non-common-grounded switched-capacitor network,a new common-grounded switchedcapacitor network is presented.Bycombining it with the basic quasi-Z-source network and quasi-switched-boost network,three new common-grounded switched-capacitor impedance source DC-DC converters are obtained.This method not only effectively improves the voltage boost capability of the converter,but also reduces the voltage stress of diodes,switches and capacitors in the impedance network.(4)Based on the internal structure characteristic of the traditional quasi-Z-source network.By embedding a complete quasi-Z-source network in the middle of another quasi-Z-source network,a new high boost quasi-Z-source impedance network is constructed.Similarly,by combining thetraditional quasi-Z-source network with the basic switched-boost network,switched-inductor,and switched-capacitor network.Two enhanced-boost quasi-Z-source inverters with active switched-inductor boost network or with active switched-capacitor boost network are proposed,respectively.Without increasing the number of the components,they can achieve common ground between input and output,reduce the input current ripple,improve the output voltage gain,and reduce the voltage stress of active switching devices.Therefore,they will be very suitable for renewable energy power generation systems.(5)Based on traditional Z-source impedance network,by adding someproper number of active and passive components(inductors,capacitors and diodes)to the impedance network,a new enhanced-boost X-type Z-network is constructed.Although the converter increases the number of devices used in the circuit,it can greatly improve the boosting capability of the converter,and effectively reduces the voltage stress of the capacitor in the impedance network,and has good practicability.