Abstract
Due to the energy crisis, global climate change and ruining of environment, a lot of countries around the world are committed to promoting renewable energy and clean energy developing. However, owning to the low output voltage characteristic of fuel cells and solar cells under low sun light, a high step-up converter is often required. In existing literature, capacitor voltage doublers are used to achieve high voltage gain. However, this kind of topology often leads to high cost and low reliability. Hence, the major motivation of this thesis is to propose a novel high step-up voltage ratio DC converter to overcome the above drawbacks. It is seen that fewer components can be used to achieve the same or even higher voltage gain. Basically, the major contributions of this thesis may be summarized as follows. First, a novel interleaved high step-up converter which integrates the advantages of the voltage doublers and coupled-inductor sophisticatedly is proposed to achieve much higher voltage gain and less voltage stress of switches. In addition, the two sets of coupling inductors are further integrated magnetically to reduce the volume and weight. Secondly, an integrated magnetic equivalent circuit is derived. Furthermore, modeling and characteristic analysis of the novel converter are made in this thesis with details. Thirdly, a 150W rating prototype with 16V input and 400V output is constructed for verifying the feasibility of the prototype converter. The resulting efficiency can be maintained above 92% as the load is varied from 35W to 150W, and the highest efficiency of 94.8% is achieved at 60W. The voltage stress of active switches is 40V which is much lower than conventional topology.