Research On The Input Series Output Series Quasi Z Source Full Bridge DC-DC Converter

In recent years, with the shortage of energy resources, and the development of power electronics integration technology, the analysis and research of the topology and control methods of the modular converter have been received more and more attention by people. The input-series output-series(ISOS) converter, which consists of multiple DC-DC modules connected in series at the input and the output, is very suitable for the high input and the high output voltage applications. In this paper,Quasi Z-source full bridge DC-DC converter(QZS-FB-DC-DC-C) is chosen as the standard module of the ISOS converter. Compared with the conventional full bridge DC-DC converter, the advantage of the QZS-FB-DC-DC-C is not only to improve the voltage conversion factor but also the utilization of DC voltage. Consequently, the Input Series Output Series Quasi Z Source Full Bridge DC-DC Converter(ISOS-QZS FB-DC-DC-C) is quite applicable to the new energy power generation. In order to ensure the stable operation of the proposed converter, the input and the output voltage sharing among modules should be employed.In this thesis, the working principle and detailed topological structure of the proposed converter are analyzed. Firstly, we reveal the relationship between the input and output voltage sharing of the modules of the ISOS-QZS FB-DC-DC-C, and then indicate that both the input and the output voltage sharing among the standard modules can be realized in the steady-state. Secondly, the terms of the voltage boost ability, the utilization of DC voltage, the modulation mode and the output powerquality for the QZS-FB-DC-DC-C are compared with conventional full bridge DC-DC converters. Furthermore, the mathematical model of the ISOS-QZS FB-DC-DC-C is also studied in this thesis. In addition, the mathematical model of quasi Z-source impedance network and the full bridge converter are established based on the average state-space and the small signal methods. The impact of parameters on quasi Z-source network dynamic performance is discussed in details. In our study, we focus on the independent output voltage control strategy and the duty cycle exchange control strategy, and analyze the stability for these two kinds of control strategy in a theoretical way. Finally, the thesis establish the performance of the proposed converter using the prototype simulation platform. The validity and effectiveness of the mathematical model and control strategies are verified by MATLAB/SIMULINK simulation. The simulation results show that the ISOS-QZS FB-DC-DC-C can keep stable in a certain range of parameters and has a good dynamic performance under the duty cycle exchanging control strategy.