In its latest report, the Intergovernmental Panel on Climate Change (IPCC) concludes that any further increase of global temperatures aggravates climate-related risks like species losses, extreme heat and humidity with significant consequences for human health, or negative impacts on food production and water availability; the projected negative outcomes escalate with higher temperature increases [1] . Therefore, worldwide efforts and international policymaking (i.e., The Paris Agreement from 2015) aim at limiting global warming by the end of the 21st century to well below +2°C above pre-industrial levels, preferably to not more than +1.5°C.

The trend towards urbanization intensifies road congestion and thus increases interest in research on urban air mobility. Electric motors enable lightweight distributed propulsion in all-electric vertical take-off and landing (eVTOL) aircraft which combine the advantages of helicopters (low operating space requirement for take-off and landing) and fixed-wing planes (efficient cruising). When aiming at ranges beyond 300 km, a hybrid power supply architecture leveraging the advantages of Fuel-Cells (FCs; with high gravimetric energy density) and batteries (with high gravimetric power density) is required, as weight is a key performance metric in airborne applications. To regulate the power flow between the two energy sources with their respective dc terminal voltages varying in a wide range, a Buck-Boost (BB) dc-dc converter is required. Such BB dc-dc converters are, however, understudied in literature and gravimetric power densities today are limited to 20 kW/kg whereas a goal of 80 kW/kg is stated for 2040. This paper systematically identifies the optimal BB dc-dc converter realization among a set of topologies with respect to weight and mission profile efficiency, considering cutting edge component technology, e.g., SiC power semiconductors and 3D printed complex geometry liquid cooled aluminum heatsinks. Two 15kW demonstrator systems with wide-bandgap power semiconductors are built and extensively tested, i.e., an all-SiC 2-level 4-switch BB dc-dc converter with 44 kW/kg and an all-GaN 3-level 8-switch BB dc-dc converter with 86 kW/kg, thus complying with the 2040 power density target and exceeding state-of-the-art BB dc-dc converter systems by a factor of four with respect to gravimetric power density.

The standard converter concept employed in variable speed motor drives is the two-level three-phase Si insulated-gate bipolar transistor voltage source inverter with its switch nodes connected to the motor terminals via shielded cables to avoid excessive high-frequency noise emissions. However, high dv/dt pulses of the inverter pose substantial stresses on the motor, which are further intensified by the ever-faster switching speeds of wide band-gap semiconductors, hence promoting interest in inverters with full-sinewave output filters, which potentially enable the use of inexpensive unshielded motor cables. However, the IEC 61800-3 standard dictates stringent conducted and radiated emission limits on unscreened power interfaces. In this article, a dc input and ac output filter structure allowing operation with unshielded cables is derived for a phase-modular 11-kW buck-boost Y-inverter motor drive system employing 1.2-kV SiC MOSFETs with a switching frequency of 100 kHz. First, regulations and measurement techniques for conducted and radiated emissions of motor drives are analyzed. Next, the operating principle of the Y-inverter is described and an electromagnetic interference equivalent circuit is derived, followed by a systematic filter design. Finally, measurements are conducted on an ultracompact hardware prototype of the converter system with 12 kW/dm ³ (197 W/in ³ ) power density, where the results indicate full compliance with the IEC 61800-3 conducted and radiated emission limits for operation with unshielded dc supply and motor cables in a residential area.

A new universal front-end PFC rectifier topology of a battery charger for Electric Vehicles (EVs) is proposed, which allows fast charging at rated and/or full power level in case of 3-phase (Europe) as well as 1-phase (USA) mains supply. In this regard, a conventional 3-phase PFC rectifier would facilitate only one-third of the rated power in case of 1-phase operation. The new topology is based on a two-level six-switch (2LB6) 3-phase boost-type PFC rectifier, which is extended with a diode bridge-leg and additional windings of the Common-Mode (CM) chokes of the EMI filter. Besides this extension of the power circuit, the general design of the new converter is explained, and the generated Differential Mode (DM) and Common Mode (CM) EMI disturbances are investigated for 3-phase and 1-phase operation, resulting in guidelines for the EMI filter design. The EMI performance (CISPR 11 class-B QP) is experimentally verified for 1-phase and 3-phase operation at an output power of 4.5 kW, using a full-scale hardware prototype that implements the proposed extensions for a 2LB6 3-phase boost-type PFC rectifier and that is designed for output power levels of 22 kW and 19 kW in case of 3-phase and 1-phase operation, respectively. Compared to a conventional 2LB6 PFC rectifier, the volume of the extended system increases from 2.7 dm${}^3$ to 3.4 dm${}^3$, of which 0.5 dm${}^3$ is due to the additional dc-link capacitance for buffering the power pulsation with twice the mains frequency occurring for 1-phase operation.

Due to the large relative permittivity of Class II dielectrics, ceramic capacitors from these materials promise significant volume and weight reductions in inverter and rectifier sine-wave filters, and are especially attractive in mobile applications that demand ultra-high power density. While previous literature found large low-frequency losses in these components, no extensible loss model was proposed to accurately characterize these ferroelectric losses. In this work, we take advantage of prior art on ferromagnetic components in power electronics to propose a Steinmetz parameter-based loss modelling approach for X7R ceramic capacitors, named the Improved Generalized Steinmetz Equation for ceramic Capacitors, or iGSE-C. This model is verified using the Sawyer-Tower circuit to measure losses in a commercially-available X7R capacitor across excitation magnitude, DC bias, temperature, excitation frequency, and harmonic injection. Losses are shown to scale according to a power law with charge, with the resulting Steinmetz coefficients valid across DC bias and slightly varying with increasing temperature. The iGSE-C accurately predicts losses for typical non-sinusoidal phase voltage waveforms with an error under 8%. Finally, the loss modeling technique is demonstrated for the sine-wave output filter of a bridge-leg arrangement with both low- and high-frequency excitations, with total capacitor losses predicted within 12% accuracy.

Latest research results on three-phase wide-bandgap (WBG) inverter systems with full-sinewave output voltage filtering are reported. A new soft-switching modulation scheme for two-level 1200 V SiC inverters is described. Furthermore, a new Figure-of-Merit for determining maximum multi-level (ML) bridge-leg efficiency is defined and low-voltage GaN devices are evaluated considering ML flying capacitor (FC) and multi-cell inverter structures. Finally, new integrated-filter buck-boost current DC-link inverter topologies are discussed.