Aviation is a significant contributor to greenhouse gas (GHG) emissions in the transportation sector. As the adoption of electric cars increases and GHG emissions due to other modes of transport decrease, the impact of air travel on environmental pollution has become even more significant. To reduce pollution and maintenance, and ensure cheaper and more convenient flights, industry and academia have directed their efforts toward aircraft electrification. Considering various types of aircraft, several frameworks have been proposed: more-electric aircraft (MEA), hybrid electric aircraft (HEA), and all-electric aircraft (AEA). In the MEA framework, propulsion is generated by a conventional jet engine; however, all secondary systems (hydraulic, pneumatic, and actuation) are electrified. By further increasing electrification, electric motors can provide propulsion with the electric power supplied by the conventional engine (i.e., HEA) or from electrical energy storage (i.e., AEA). Power electronics and electrical machines play a key role in this scenario in which electric power must be efficiently generated, distributed, and consumed to satisfy extremely high requirements of aviation safety. This article provides an overview of recent advancements in aircraft electrification, and trends and future developments referenced to the global aviation roadmap.

Modular power converters in combination with distributed control architecture has been promising in medium-voltage applications due to its modularity and scalability. The requirement of the synchronization accuracy is elevated dramatically for the communication network with advanced distributed control schemes. This paper presents a phase-locked loop (PLL)-based synchronization method with sub-ns synchronization accuracy based on the White Rabbit protocol. Digital perturbation injection method is proposed to estimate the PLL closed-loop characteristics, and the PLL stability is analyzed. Good agreements of the closed-loop transfer function and stability analysis have been achieved between the theoretical calculation and experimental results. A four-PEBB 6kV SiC-based converter is established to verify the distributed communication and control system.

Impedance-based stability criterion has been proven to be a powerful tool for small-signal stability analysis and design, derived from Nyquist stability criterion and first developed in dc-dc power electronics converter systems. Recently it has been extended to ac systems to address the issues and challenges coming with more and more power electronics based converters connected to the existing ac power grids, either in transmission or distribution level. With that, only terminal information is sufficient to judge small-signal stability, which can be from either impedance model or experimental results. Therefore, internal details of inverters are not necessary, facilitating the system operator to integrate. This paper specifically presents a case study with multiple STATCOMs in IEEE 14-bus system to illustrate the application of the d-q frame impedance-based stability criterion. It shows that the impedance-based stability criterion can predict the small-signal stability with accurate oscillatory frequency for STATCOMs' interactions, and a new instability pattern was found from the impedance point of view.

Small-signal models of impedances for grid-tied converters have recently attracting researchers' attention and shown of great importance in stability analysis. This paper proposes the impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current and voltage loops and reveals the significant features compared to other types of grid-tied converters that the 1) grid impedance should be taken into account because of regulated point of common coupling voltage, 2) full impedance matrix due to nearly zero power factor and 3) flipped polarity of impedances at low frequency as a result of inversed direction of reactive power. All these characteristics render difficulty in applying stability criterion. The model was verified experimentally with a scaled-down STATCOM prototype.

This paper presents a complete design procedure for a motor drive aiming at maximizing nominal power within loss (30 W) and form factor (60 inch3) constraints. Particularly, this motor drive system has EMI requirement on both input and output sides and it should be free convection cooled. Loss-size Pareto fronts of multiple three-phase topologies including two-level voltage source converter (VSC), three-level neutral point clamped (NPC) converter, T-type converter and three-phase capacitor-decoupled triangular conduction mode (TCM) converter are explored in order to find the optimized design. Pareto fronts under different power level shows a maximum of 5 kVA power could be achieved by T-type converter within given limits and requirements. T-type converter is accordingly selected and constructed. A power density of 80 W/inch3is achieved by the prototype. Finally, experimental results obtained with the free convection cooled converter prototype are presented for validating purposes, demonstrating the 99.2% efficiency (42.3 W loss) at nominal load.

Stability margins of the switch-mode DC/DC power conversion systems are very sensitive to variations in load and system parameters. In aerospace applications these systems can be exposed to considerable variations in temperature that can cause large changes in system parameters from their nominal values and can lead to stability problems if this issue is not properly taken into account during the design phase. In this study robust stability margins are calculated for a system that consists of a DC/DC closed loop buck converter and an input LC filter considering extreme variations in temperature. For the prototype system, the paper details a modelling approach to developing an uncertain system model which is used to assess robust stability based on the principle of Structural Singular Value. The approach is verified through simulations in MATLAB and through experimental tests.

This paper presents some of the key advances in power electronics pertaining to shipboard electric power system applications. The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives. Their benefits on power converter efficiency and power density are explained through a case study of a medium-voltage (MV) class motor drive system. SiC and GaN also enable new applications, including solid-state transformers, while posing new design and application challenges such as gate drive, protection, and interaction with loads. In addition to device related topics, this paper also overviews other important advances in power electronics, including topology, control, passive components, thermal management, filters, and packaging. The significance of power electronics building blocks (PEBBs) concept for shipboard power system development is discussed. Recognizing the growing complexity of shipboard power systems, some system-level technologies related to future MV direct current (dc) system architecture are highlighted.

This paper investigates the design procedure of cascaded H-bridge (CHB) and modular multilevel converter (MMC) topologies for medium-voltage and high-power industrial motor drive application. The design is performed using 1.7-kV insulated gate bipolar transistor (IGBT) technology. A model is derived for multi-pulse transformer to take into account its leakage parameters' effect on converter design. Also a comparison is done between MMC and CHB topologies at three different voltage levels: 4.16-, 6.9- and 13.8-kV and three different power levels: 1-, 3- and 5-MVA Comparison is done from several points of view like capacitance requirements, diode front-end and inverter stage losses, semiconductor rating and junction temperature and parts count.

This paper proposes a detailed step-by-step design procedure for the input and output EMI filter of a matrix converter (MC) driving a 30 kW permanent magnet synchronous motor. The procedure involves modeling the EMI source and conduction path in the frequency domain, the design of the passive components, and the estimation of the EMI filter weight and volume. Finally, a weight comparison between the MC and alternative two- and three-level back-to-back converters is presented showing the significant advantage offered by the MC in this regard; namely a 30 % and 50 % lower weight than its three-and two-level counterparts. Time and frequency domain simulations are used for verification purposes.

This paper demonstrates that a droop controller, which is fundamental to the operation of power systems and now the parallel operation of inverters, is intrinsically the same as a phase-locked loop (PLL), which is widely adopted in modern electrical engineering. This bridges the gap between the two communities working on droop control and PLLs. As a result, droop controllers and PLLs can be improved and further developed via adopting the advancements in the other community. This also offers insightful understanding to power systems that have inverters and generators mixed together and leads to significant technological breakthrough for the grid connection of renewable energy. For example, there is no longer a need for grid-connected inverters to have a phase-locked loop and a droop controller at the same time.