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Medium-frequency power transformers are used in DC-DC converters topologies such as photovoltaic, wind turbines, fuel cells, electric vehicles and uninterruptible power supply systems. In the design of magnetic circuit components such as transformer and inductor, the choice of the core material is of great importance in terms of losses and magnetic induction. For determining the size of the medium-frequency transformer, frequency and magnetic flux density are also two key parameters. In this study, the core volume change with the frequency is mathematically analyzed and modeled by using finite element analysis method. Parametric analysis provides very useful information in order to determine the excitation voltage level, which does not cause the saturation in the core, for the switching frequency. Thus, parameters of the designed transformer equivalent circuit can be optimized. Then, medium-frequency transformer is operated in power electronic circuits and saturation effect and core losses according to the preferred magnetic materials are investigated by performing co-simulation.

As a result of advances in power electronics, in medium to high frequency high power conversion has become widespread. The performance and the sizing of the medium-frequency power transformer vary depending on material properties and operating frequency. While the core size determined by the power requirements, the specific core loss which varies depending on the frequency and the flux values becomes important. On the other hand, power handling capability of transformer varies according to the core material type and operation frequency. In this study, %3 SiFe 0.1mm material was compared with the nanocrystalline material for the medium-frequency transformer cores. SiFe and nanocrystalline core materials are modeled, tested and analyzed for the different frequency values. Thus, the relationship between the frequency increase with the power handling capability and core losses were uncovered.

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Grid connected inverters with LCL output filters are widely used in exporting energy generated from renewable energy sources. The LCL filter and inductors used in this filter has important effect on inverter performance. Although it is different in high power levels nowadays, powder cores are commonly used in inductor design in low and medium power levels. In this study, inductors for LCL filter of the gridconnected inverter are designed. The co-simulation studies are performed and performance and losses of the designed filter is analyzed for two-level and three-level inverter topologies. It is seen that, total losses of the LCL filter of three-phase three-level inverter is 35.9% lower than two-level inverter.