The issues of global warming and environmental pollution caused by the fossil fuels led to applying renewable energies as an alternative energy solution. One of the best renewable energy sources are photovoltaic (PV) sources. Since the output voltage of PV sources are very low, they are not suitable to supply grid tied inverters. Furthermore, the output power of the solar systems is not continuous and in cloudy weather or at night PV panels can’t provide the output demanded power. Thus, in these conditions, a secondary energy source such as wind source or an energy storage device such as battery is needed. Due to the problems mentioned above, a hybrid energy system which apply more than one power source is needed to provide output power. In hybrid energy systems each energy source needs an independent DC/DC converter as the interface circuit to absorb its power and transfer it to the DC bus. However, using multi-input converter instead of several independent DC/DC converters for each input energy source includes several advantages, such as decreasing the count of components, the converter size, final manufacturing cost and system power losses. Due to the listed advantages, multi-input converters have founded more attention by researchers and several topologies of them are proposed in recent years. The goal of this thesis is proposing a new high step up multi input converter and also a new zero voltage switching (ZVS) high step up multi-input converter by using of high step up techniques, current fed input stages and an auxiliary circuit to provide soft switching. The proposed converter can boost the voltage of input sources to a regulated output DC voltage. The input currents of the proposed converter are continuous which leads to the reduction of input filter volume in solar systems. In the proposed converter, all input sources can transfer power to the load simultaneously or individually. An auxiliary circuit is used to provide the soft switching conditions for main switches and reduce switching losses. Unlike the conventional high step up multi-input converters, the proposed converter has a simple structure. In this thesis, the proposed topologies and the different operating modes of them are presented in details. Also, the experimental results obtained from the converter prototype are presented to verify the theoretical analysis. Keywords Multi Input Converters, High Step up, Soft Switching Techniques, Zero Voltage Switching
