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This paper presents a management strategy of an isolated phase-shifted DC-DC buck converter (270V/28V, 5kW, 100kHz) used as a Li-ion battery charger for more electric aircraft. Three PI control loops are involved: An inner loop for the converter's output current, an outer loop for the battery charge current in case it is connected, and another outer loop for converter output voltage control when the battery is disconnected and only auxiliary LVDC loads need to be fed. The main contribution herein, is the control mode transition supervisor (CMTS) that communicates with the battery management system (BMS) through CAN and SCI interfaces, in order to safely switch between the control modes, depending on its presence on the network and its state of charge. Stability of the PI loops is guaranteed using Bode's stability criterion in frequency domain. Effectiveness of the proposed management strategy is verified through simulation and experimental validation.
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... To fulfil all the emission and fuel consumption requirements while also meeting those for aircraft safety, new architectures are needed. Currently, the most popular alternative that researchers are working on from a range of perspectives is the More Electric Aircraft (MEA) initiative [9,10,11,12]. Table 2 presents the main differences between traditional and the expected future aircraft. Table 2 demonstrates that electric systems will replace non-electrical ones in near future. ...
In the last few years, the More Electric Aircraft concept has been proposed as a solution not only for increasing the efficiency of the entire aircraft, but also for reducing CO2 and NOx emissions. However, to purse the increased electrification of aircraft, certain challenges, such as safety, security and reliability, need to be overcome. In the literature, component redundancy is usually proposed as the only way to improve aircraft safety. However, this paper presents a method that allows the concept of redundancy to be replaced by the combination of a new algorithm and a recently developed device, which makes it possible to decentralize the traditional aircraft power system architecture, thereby increasing fault tolerance on aircraft. This algorithm detects where the fault takes place, calculates new hardware configuration options based on minimizing power losses, decides which choice is the optimal one and reconfigures the system to avoid the detected fault. To analyse whether the proposed methodology works properly, a series of tests were run in a MATLAB ® simulator. The results show that the decentralized algorithm is able to find alternative paths and continue operating powered loads when a fault occurs in aircraft DC power systems.
In this paper a More Electric Aircraft (MEA) electric power system is modeled and simulated with a fuel cell/battery hybrid Auxiliary Power Unit (APU). Fuel cell/battery hybrid power source is connected at the AC-load bus bar of 200-VAC and 400-Hz. Due to the DC output of the hybrid power source, a 12-pulse inverter is used at the output of the APU. The two output voltages of the generator-channel inverter and the hybrid-source inverter must be synchronized. The output of the fuel cell is controlled using a DC/DC boost converter to provide the aircraft DC bus voltage of 270-V. The battery is controlled by using a bidirectional DC/DC converter to provide the excess load when necessary and be charged from the fuel cell during normal
operating conditions. To make the aircraft electric power system compatible with the aircraft standards, an active power filter (APF) is connected at the synchronous generator terminals. The APF reduced the total harmonic distortion (THD) of the generator voltage and current to be within the standard values. The studied aircraft electric power system with the proposed fuel cell/battery hybrid system is simulated without and with the presence of the APF and it is found that the APF reduced the voltage and frequency transients of the system and improves the aircraft electric system performance.
Energy storage systems provide viable solutions for improving efficiency and power quality as well as reliability issues in dc/ac power systems including power grid with considerable penetrations of renewable energy. The storage systems are also essential for aircraft powertrains, shipboard power systems, electric vehicles, and hybrid electric vehicles to meet the peak load economically and improve the system's reliability and efficiency. Significant development and research efforts have recently been made in high-power storage technologies such as supercapacitors, superconducting magnetic energy storage (SMES), and flywheels. These devices have a very high-power density and fast response time and are suitable for applications with rapid charge and discharge requirements. In this paper, the latest technological developments of these devices as well as advancements in the lithium-ion battery, the most power dense commercially available battery, are presented. Also, a comparative analysis of these high-power storage technologies in terms of power, energy, cost, life, and performance is carried out. This paper also presents the applications, advantages, and limitations of these technologies in a power grid and transportation system as well as critical and pulse loads.
Similar to the efforts to move toward electric vehicles, much research has focused on the idea of a more electric aircraft (MEA). The motivations for this research are similar to that for vehicles and include goals to reduce emissions and decrease fuel consumption. In traditional aircraft, multiple systems may use one type or a combination of types of energy, including electrical, hydraulic, mechanical, and pneumatic energy. However, all energy types have different drawbacks, including the sacrifice of total engine efficiency in the process of harvesting a particular energy, as with hydraulic and pneumatic systems. The goal for future aircraft is to replace most of the major systems currently utilizing nonelectric power, such as environmental controls and engine start, with new electrical systems to improve a variety of aircraft characteristics, such as efficiency, emissions, reliability, and maintenance costs. This paper provides an in-depth look into how the systems have-or will be-changed. Future aircraft capabilities such as electric taxi and gas-electric propulsion for aircraft are also included for discussion. Most recent commercial transport aircrafts are described as the current state-of-the-art electric aircraft system. Future goals, including those of NASA, are presented for future advances in MEA.
High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc–dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.
This paper presents a comparative analysis of different energy management schemes for a fuel-cell-based emergency power system of a more-electric aircraft. The fuel-cell hybrid system considered in this paper consists of fuel cells, lithium-ion batteries, and supercapacitors, along with associated dc/dc and dc/ac converters. The energy management schemes addressed are state of the art and are most commonly used energy management techniques in fuel-cell vehicle applications, and they include the following: the state machine control strategy, the rule-based fuzzy logic strategy, the classical proportional-integral control strategy, the frequency decoupling/fuzzy logic control strategy, and the equivalent consumption minimization strategy. The main criteria for performance comparison are the hydrogen consumption, the state of charges of the batteries/supercapacitors, and the overall system efficiency. Moreover, the stresses on each energy source, which impact their life cycle, are measured using a new approach based on the wavelet transform of their instantaneous power. A simulation model and an experimental test bench are developed to validate all analysis and performances.
In phase-shifted full-bridge (PSFB) converter, using discontinuous conduction mode (DCM) is one of the most effective ways to improve efficiency in the light load condition. DCM of the PSFB converter allows getting reduced the duty ratio and zero voltage switching (ZVS) in the light load condition. Because of its simplicity, commercial IC adapted DCM by turning-off synchronous rectifiers (SRs). However, turning-off SRs causes large conduction losses in body diodes of SRs, and ZVS condition or optimized dead time are not defined yet. This letter proposes to use “AND-gated” control signals for SRs to reduce conduction losses in body diodes. Also, the ZVS condition is presented to design dead time easily. The feasibility of the proposed technique has been verified with 90-265 Vac input, 400 V link voltage, and 12V/750 W output server computer power supply system.
The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO2 emissions on global climate constitute a major challenge for the 21st century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today's lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40–80 mile all-electric range, and all-electric vehicles (EVs) with a 300–400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithium-ion systems; factors of five or more may be possible for lithium–oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.
This paper describes the main trends and future challenges of electrical networks embedded in "more electrical aircraft" especially in the fields of industrial electronics and energy conversion. In the first part, the current context and new standards are put forward, emphasizing the main evolutions on aircraft architectures, from AC fixed frequency networks, variable frequency to "Bleedless" architectures. The main characteristics of more electrical aircraft are discussed, especially in terms of power management rationalization, maintenance, health monitoring capacity, etc. The second part deals with the new trends and challenges of "more and more" electrical aircraft linked with power integration and new architecture with HVDC standard. Recent methodological orientations towards "Integrated Optimal Design" are discussed with representative examples. Finally, new trends towards reversible and hybrid HVDC networks including new storage devices are also emphasized.