Filter design of high power density converter with weight, size and thermal considerations

Adopting more efficient electric technologies in the aircraft industry has been gaining attention with the objectives to decrease fuel consumption and reduce environmental impact. The backbones of more electric technologies are power converters to interface between loads and power grids. For aerospace applications, these power converters must be both compact and light, and hence, realization of high power density converter (HPDC) is necessary. Pulse width modulation (PWM) technique with high switching frequency is commonly employed in HPDC design but it results in large harmonic contents. To achieve high power density, increasing the switching frequency of the power converter has also become a necessity. Hence, practically all HPDCs require passive filters to meet the stringent power quality requirements. For all the filter configurations, LCL filter is the most popular choice in grid-connected power converter systems for its excellent performance. However, it is also a major contributor of the overall weight of an HPDC, especially the inverter-side inductor, which requires to suppress higher frequency harmonic contents at the inverter side. The main focuses of this thesis are to explore various design techniques in size and weight reduction of passive filters. Then, the benefits of interleaving three phase voltage source converters (VSCs) are presented to improve the power density. To further improve power density of HPDC, different levels with power converter includes two-level, three-level, and five-level configurations will be investigated, with two types of three-phase power grids, the three-phase three-wire and three-phase four-wire power grids. Lastly, the common mode inductor, includes the extraction of common mode (CM) and differential mode (DM) inductances are analysed by using 3D finite element method (FEM). The effects of CM and DM currents on the magnetic core saturation, the parasitic capacitance of a CMC, and different core structures on the performance are evaluated. In addition, the high density and liquid-cooled CMC are also analyzed with computational fluid dynamics (CFD) and ANSYS Fluent.Doctor of Philosophy (EEE