In this paper, a decentralized energy management strategy (EMS), which is derived from the conventional droop control, is proposed for the auxiliary power unit composed of multiple fuel cells (FCs) and supercapacitors (SCs) of a more electric aircraft. By utilizing a virtual inductor droop scheme to the FC converter and a virtual resistor droop scheme to the SC converter, the proposed EMS is able to split the load power automatically into low and high frequency components and allocate them to the FC and SC units, respectively. In addition, by optimally designing the droop parameters, accurate power sharing among different source units is achieved. The proposed strategy is not only suitable for extending the service life of the system by adding SoC protection mechanism in the energy management, but also can improve the system reliability as it is compatible for the disconnection of some source units when fault occurs. The operational principle of the proposed EMS and the detailed system design methodology are elaborated, followed by which hardware-in-the-loop simulation study based on Typhoon HIL 602 is done to verify its validity.

Multipulse ac/dc rectifiers (MPRs) are widely used in aviation applications due to their rugged structure, cost effective, and high-reliability features. In this article, an overview of the recent advances and trends on the MPR technology, mainly the autoconfigured transformer-based MPRs, and its application in more electric aircrafts is performed. This article covers system topologies, transformer configurations, passive and active harmonic reduction schemes, case study, practical selection and design guidelines, and applications. To fairly evaluate the performances of MPRs with different pulse numbers, necessary simulation studies are carried out under comparable conditions, including power rating, input and output specifications, and transformer configuration. Then, an 18-pulse asymmetric delta-polygon configured prototype is established based on the simulation evaluation and experimental verification is performed. It is expected that this article can provide a broad perspective on MPR technology, and, in particular, highlight the latest emerged technology that significantly promotes the performances of MPRs. More importantly, it is desired that the results obtained in this article can provide an effective selection guideline and design suggestion for researchers and engineers engaged in designing MPRs, especially for aviation applications.

Multi-pulse autotransformer rectifier unit (ATRU) has been widely used in aviation applications due to its rugged structure, cost effective, and high reliability features. In this paper, up to six types of autotransformers for 18-pulse ATRU are investigated, aiming to provide an optimal selection guideline for a proper structure. By conducting a thorough comparative study on the kVA rating of the autotransformers and current harmonic characteristics over a wide voltage step-up or step-down range, the asymmetric delta-polygon (DP) structure is considered as the most promising choice. Subsequently, an example 18-pulse ATRU with such structure is adopted as the front-end of an AC/AC converter powering an onboard hydraulic pump. After analyzing the operational principle, accurate mathematical expressions among the overall voltage gain K, the total harmonic distortion (THD) of the line current, and the kVA rating of the autotransformer were carefully deduced. Before conclusions, the theoretical analyses were verified by simulations and experiments. It is shown that the THD of the input line current of the designed 10-kW ATRU is 6.74the rated efficiency reaches 98.5%, and the autotransformer’s weight is merely 3.3 kg.

For the fuel cell-battery-ultracapacitor hybrid energy storage system applied to the transportation electrification system, its energy management system (EMS) has to achieve the expected energy management objectives, including dynamic load power-sharing, state-of-charge regulation of battery and ultracapacitor, regenerative braking capability, etc. Conventionally, such an EMS is achieved in a centralized or hierarchical way, resulting in poor flexibility, scalability, and reliability. In this article, a completely decentralized EMS, which is achieved based on a modified mixed droop control, is proposed to achieve the above objectives. As the implementation of the proposed EMS does not rely on any communication links or common signals, the system cost is reduced. Besides, the system with the proposed EMS is of high reliability as it can still operate well during the outage of one power source due to malfunction. The operational principle of the decentralized EMS is analyzed in detail, followed by which the system design is elaborated. In the end, the feasibility and effectiveness of the proposed EMS are verified by experimental results.

To satisfy the ever-growing stringent requirement on the power quality of on-board electric power system, a novel parallel configured 48-pulse rectifier, which is formed by two 24-pulse rectifiers connected in parallel through a tapped and coupled interphase reactors respectively, is proposed. Through the comprehensive harmonic analysis on the proposed rectifier, it is revealed that the 23rd and 25th harmonics generated by the two 24-pulse rectifiers are equal in magnitude while opposite in direction, which evidently enables the 48-pulse operation. To better understand the performances of the proposed rectifier, its input current, output voltage, kVA rating, and power losses of magnetic devices are analyzed in detail. Afterward, the validity of the theoretical analysis is verified by simulation and experiment. The results confirm that the proposed 48-pulse rectifier has superior harmonic reduction ability, high reliability, and high power density. More importantly, due to the parallel structure, it also features high fault-tolerant ability, which makes it very suitable for aviation or aerospace applications.

Zero voltage switching (ZVS) of power semiconductor devices is an effective way to improve the efficiency and power density of the power electronic converters with extremely high switching frequency. This article aims to analyze and realize the true full-range ZVS operation of a totem-pole power factor correction circuit. The available ZVS control strategies are investigated, and the conditions for the realization of full-range ZVS operation are analyzed. It is revealed that the existed control strategies did not consider the influence of the dead-time, resulting in the failure of ZVS operation in some input voltage ranges. To address this issue, two feasible retrofitted control strategies, namely the turn- off current optimization control and the adaptive dead-time control, are proposed. The merits and drawbacks of the two control strategies are carefully analyzed and compared. It is found that the adaptive dead-time control can not only achieve the true full range ZVS but also significantly reduce the loss of the freewheeling diodes. The design consideration of key parameters is discussed. Finally, the feasibility of the proposed control and the correctness of the theoretical analyses are verified by simulation and experiment.