Study On High Step-up Three-level Zeta Converter

With the development and application of the green energy such as photovoltaic power generation system and fuel cell, more and more scholars at home and abroad focus on the studying of the DC-DC converter with the high voltage gain. The threelevel DC-DC converter has advantages of reducing the voltage stress of the diodes and the switches and also the filter size, compared with the two-level DC-DC converters. However, three-level DC-DC converter has the same voltage conversion ratio with the two-level DC-DC converter. In order to improve their boost abilities which are strictly limited by the interactions caused by the circuit topologies and power switches, this paper proposes a new type of TL Zeta DC-DC converter. The proposed converter is a DC-DC converter with a double self-lift coupled-inductor cell instead of the inductor of the converter. The proposed converter achieves a high-voltage conversion ratio with maintaining advantages of the traditional TL Zeta converter.Firstly, this paper changes the two-level zeta converter into the three-level one with the principle of the three-level DC-DC conversion and analysis the theory of the threelevel zeta converter. Moreover, Matlab simulation and the experimental results proved the validity of the three-level zeta converter.Secondly, in order to improve the voltage gain of converter, this paper introduce the switched-inductor, the self-lift switched-inductor and the double-self-lift switchedinductor instead of the inductor into the three-level zeta converter, then this paper analysis the theory of the proposed converter and simulate it with the Matlab software. At last, experimental results verify the voltage conversion ability of the double-self-lift converter.Finally, this paper introduces the coupled-inductor cell for the purpose of reducing the limiting of the duty ratio to the voltage conversion of the circuit. The inductor of the double-self-lift cell was replaced by the switched-coupled-inductor. Furthermore, the topology of the converter was improved to a new three-level coupled-inductor with double-self-lift. The turn ratio in the new circuit reduces the function of the duty ratio to the voltage gain. Then, the Matlab simulation and the experimental result are provided to demonstrate the validity and feasibility of the new converter.The double-self-lift coupled-inductor cell can be applied into the other traditional DC-DC converter, which has important significance for the studying of DC-DC converter with the high voltage gain.