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Research On Z-source Inverter

Posted on:2009-08-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y TangFull Text:PDF
GTID:1102360302989962Subject:Power electronics and electric drive
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The Z-source inverter can perform buck-boost conversion and the phase legs can be on shoot-through state, therefore it can be widely used in renewable energy power supply system, but the present Z-source inverter has the drawbacks of high Z-source capacitor voltage stress and huge inrush surge.The research of this dissertation focus on the new Z-source converter structure and design method of Z-source converter topologies. The new topologies, operation principle, characteristic and control strategy of the single-phase Z-source inverter, three-phase Z-source inverter and Z-source AC-AC converter are investigated systematically.A new Z-source converter structure is proposed and a series of new Z-source converter topologies are derived based on the topological design method. Compared to existing topologies, the new topologies can achieve less volume, weight and cost. The application of the Z-source network in single-phase inverter is researched. The single-phase Z-source inverter topologies are proposed, including the basic topology, the simplified topology and the buck-boost topology. The basic and simplified topologies only utilize two switches with the input and output sharing the same ground. Analysis is given taking the simplified topology as an example. One-cycle control is adopted and is verified by experimental results. The buck-boost topology utilizes three switches and has two operation modes: buck mode and boost mode. It can perform the single-stage buck-boost conversion with continuous input current and bidirectional power flow.An improved three-phase Z-source inverter topology and its soft-start strategy are proposed to solve the problems in traditional topology. The system volume and cost can be reduced and the reliability can be improved. The characteristic of improved topology under various SPWM and SVPWM control is investigated. The operation principle under discontinuous conduction mode (DCM) is analyzed and the condition in DCM mode is derived. The parameters design rule is given. A prototype is built on and the experimental results are given.The small signal model of the new three-phase Z-source inverter is derived and the transfer function of system is given. The effect on right-hand-plane zero caused by different parameters is analyzed based on loot-locus analyses. The present closed loop control strategy of Z-source inverter is complex and not always stable. A new feed-forward of input plus feedback of peak output control strategy is proposed, and the control of DC-link and inverter stage is decoupling. This control strategy is simple and stable, and there is no steady-state error in ac output. The analysis is verified by experimental results.Finally, the analysis is given on Z-source AC-AC converter. A new family of single phase four switches structure and three phase six switches structure Z-source AC-AC converters are proposed to solve the drawbacks of high conduction loss and commutation problem in present Z-source AC-AC converters. They have the merits such as simple structure, high efficiency, high reliability and safe commutation can be achieved. The operation principle, commutation modes and parameter design method are analyzed. Experimental results on voltage-fed single phase Z-source AC-AC converter are given to verify the analysis.
Keywords/Search Tags:inverters, Z-source, circuit topologies, modulation schemes, control strategy, soft-start, shoot-through, small signal model, one-cycle control, right-hand-plane zero, feed-forward control, AC-AC converters, commutation
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