Today heavy dependence of the industry on electrical energy and increasingly fast depletion of fossil fuel sources has created the need for a proper substitute energy source. One of the best choices for this matter is the renewable energy sources like solar energy. The most common way of converting the solar energy to electrical energy is by the means of solar panels or solar cells. The electrical energy required by the consumers is of high voltage AC type. However, the amount of electrical voltage produced by these solar panels is of low voltage DC type, which means there should be a voltage boosting phase in the power generation procedure. This phase is usually done with different methods such as series connection of the solar panels, low frequency AC transformers at the DC/AC converter’s output, using of high gain DC/DC converters and series connection of DC/DC converters. In this thesis, high power high step up DC/DC converters are the main focus. Due to the reasons such as low power demand, parasite capacitance of the panels and local shadow effect the number of series connected solar panels can be small, therefore Such converters are a suitable choice for converting the low output voltage of a single or multiple solar panels to a high DC voltage required by the DC/AC converters. From the wide range of DC/DC converters, the ones with high gain and low input current ripple are a suitable for this application. To achieve the mentioned goals, the advantages of the coupled inductors and autotransformer application in converters are used on a basic SEPIC converter to increase the output voltage gain without increasing the voltage stress of the switch. In this thesis, first an overview of methods and converters proposed for high power and high voltage gain applications in various papers is given. Then, the proposed isolated SEPIC converter with coupled inductor is introduced and the operational modes and the equations required for converter design is explained along with soft switching conditions applied on it. In the following, the proposed non isolated SEPIC converter with coupled inductors is described. For the hard switching conditions of the converter, experimental results obtained by a 200W converter are proposed along with the ones obtained in simulations. Also experimental and simulation results are given for the first proposed converter on 360W. Keywords: High step-up DC/DC converter, SEPIC converte, Coupled inductors, Active clamp, Photovoltaic system,.
