Multiple-output DC–DC converters: applications and solutions

Multiple-output DC–DC converters are essential in a multitude of applications where different DC output voltages are required. The interest and importance of this type of multiport configuration is also reflected in that many electronics manufacturers currently develop integrated solutions. Traditionally, the different output voltages required are obtained by means of a transformer with several windings, which are in addition to providing electrical isolation. However, the current trend in the development of multiple-output DC–DC converters follows general aspects, such as low losses, high-power density, and high efficiency, as well as the development of new architectures and control strategies. Certainly, simple structures with a reduced number of components and power switches will be one of the new trends, especially to reduce the size. In this sense, the incorporation of devices with a Wide Band Gap (WBG), particularly Gallium Nitride (GaN) and Silicon Carbide (SiC), will establish future trends, advantages, and disadvantages in the development and applications of multiple-output DC–DC converters. In this paper, we present a review of the most important topics related to multiple-output DC–DC converters based on their main topologies and configurations, applications, solutions, and trends. A wide variety of configurations and topologies of multiple-output DC–DC converters are shown (more than 30), isolated and non-isolated, single and multiple switches, and based on soft and hard switching techniques, which are used in many different applications and solutions.info:eu-repo/semantics/publishedVersio

An Integrated Thermal-Electrical Model for Simulations of Battery Behavior in CubeSats

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A Comparative Tradeoff of Electric Power System Architecture Reliabilities in CubeSat Satellites

Small nanosatellites, such as CubeSats, represent an important population of satellites that are currently commissioned in various types of scientific research missions in space travel. CubeSats are small cubic satellites that can vary in size and are most commonly deployed in the “1U” size, measuring one cubic meter. CubeSats are important in scientific research as they follow a standardized design specification, known as the CDS, which aims to normalize the cost of development and deployment, as well as act as a baseline design specification for a community of researchers, students, and inventors. The advent of CubeSat development has enabled thousands of researchers to conduct space missions, which had otherwise been too expensive and resource intensive. For CubeSats, the Electric Power System (EPS) has been documented as being the most unreliable sub-system in the CubeSat architecture. Further, it is the most critical sub-system, as a CubeSat cannot function without the EPS performing its intended functionality. While the CDS provides guidelines for CubeSat development, there is flexibility. The intent of this thesis is to analyze the reliability impact of proposed alternative EPS architectures compared to the current implementation. Alternative architectures consist of the same components as the baseline, but are arranged in varying configurations and quantities. A comparative study is performed between ten alternative EPS architectures against a baseline by determining the failure rate and Mean Time To Failure (MTTF) for each configuration. Reliability calculations are supported by determining each architecture minimal cut set and developing a corresponding Reliability Block Diagram. After, an analysis of the pros and cons between the alternative variants and the baseline is discussed. The proposed alternative architectures investigate the reliability impact of implementing distributed architectures, where redundant components and common connection busses are integrated to introduce varying levels of redundancy and operational flexibility

Енергоефективне керування електроживленням систем наносупутників

Дисертаційна робота присвячена розробці систем керування електроживленням наносупутників, методів формування циклограм роботи, вибору способів розв’язку сформованих математичних рівнянь максимізації запасу енергії наносупутника або його залишкового часу роботи, а також оптимізації його циклорами за вказаними вище критеріями максимізації запасу енергії або залишкового часу роботи. В роботі автором запропоновано методику побудови системи електрозабезпечення супутника «POLYTAN-1» НТУУ «КПІ» з урахуванням розроблених алгоритмів максимізації запасу енергії. Її особливістю, крім запропонованих методів максимізації, є такий варіант з’єднання сонячних батарей, який збільшує ККД та відмовостійкість системи. В роботі наводиться опис розробленого програмного забезпечення, для реалізації запропонованих методів побудови циклограм. Обчислена з його застосуванням циклограма керування наносупутника «POLYTAN-1» дозволяє збільшити час роботи супутника в штатному режимі на 3,2 місяці або на 29%

Energy efficiency in LEO satellite and terrestrial wired environments

To meet an ever-growing demand for advanced multimedia services and to support electronic connectivity anywhere on the planet, development of ubiquitous broadband multimedia systems is gaining a huge interest at both academic and industry levels. Satellite networks in general and LEO satellite constellations in particular will play an essential role in the deployment of such systems. Therefore, as LEO satellite constellations like Iridium or IridiumNEXT are extremely expensive to deploy and maintain, extending their service lifetimes is of crucial importance. In the main part of this thesis, we propose different techniques for extending satellite service life in LEO satellite constellations. Satellites in such constellations can spend over 30% of their time under the earth’s umbra, time during which they are powered by batteries. While the batteries are recharged by solar energy, the Depth of Discharge (DoD) they reach during eclipse significantly affects their lifetime – and by extension, the service life of the satellites themselves. For batteries of the type that power Iridium and Iridium-NEXT satellites, a 15% increase to the DoD can practically cut their service lives in half. We first focus on routing and propose two new routing metrics – LASER and SLIM – that try to strike a balance between performance and battery DoD in LEO satellite constellations. Our basic approach is to leverage the deterministic movement of satellites for favoring routing traffic over satellites exposed to the sun as opposed to the eclipsed satellites, thereby decreasing the average battery DoD– all without taking a significant penalty in performance. Then, we deal with resource consolidation – a new paradigm for the reduction of the power consumption. It consists in having a carefully selected subset of network links entering a sleep state, and use the rest to transport the required amount of traffic. This possible without causing major disruptions to network activities. Since communication networks are designed over the peak traffic periods, and with redundancy and over-provisioned in mind. As a remedy to these issues, we propose two different methods to perform resource consolidation in LEO networks. First, we propose trafficaware metric for quantifiying the quality of a frugal topology, the Maximum Link Utilization (MLU). With the problem being NP-hard subject to a given MLU threshold, we introduce two heuristics, BASIC and SNAP, which represent different tradeoffs in terms of performance and simplicity. Second, we propose a new lightweight traffic-agnostic metric for quantifiying the quality of a frugal topology, the Adequacy Index (ADI). After showing that the problem of minimizing the power consumption of a LEO network subject to a given ADI threshold is NP-hard, we propose a heuristc named AvOId to solve it. We evaluate both forms of resource consolidation using realistic LEO topologies and traffic requests. The results show that the simple schemes we develop are almost double the satellite batteries lifetime. Following the green networking in LEO systems, the second part of this thesis focuses on extending the resource consolidation schemes to current wired networks. Indeed, the energy consumption of wired networks has been traditionally overlooked. Several studies exhibit that the traffic load of the routers only has a small influence on their energy consumption. Hence, the power consumption in networks is strongly related to the number of active network elements. In this context, we extend the traffic-agnostic metric, ADI, to the wired networks. We model the problem subject to ADI threshold as NP-hard. Then, we propose two polynomial time heuristics – ABStAIn and CuTBAck. Although ABStAIn and CuTBAck are traffic unaware, we assess their behavior under real traffic loads from 3 networks, demonstrating that their performance are comparable to the more complex traffic-aware solutions proposed in the literature

Design and Management of Satellite Power Systems

Abstract—Satellites are indispensable for broadcast, weather forecast, navigation, and many other applications, but their design entails a number of stringent requirements, such as limited space and weight, impossible/costly online repairs, severe radiation, and a wide range of temperature they have to withstand. These requirements can only be met by an effective, robust co-design of physical and computing (control) parts of each satellite, making them prototypical cyber-physical systems (CPSes). Of the various CPS issues related to satellites, this paper focuses on offline design and online management of satellite power systems. Specifically, we analyze and model unique characteristics of power supply and demand of a satellite, which are dictated by the periodicity of power generation from solar panels and the nonlinear behavior of rechargeable battery cells. Based on the understanding of these characteristics, we first propose how to find the best configuration (e.g., the number, the arrangement, and the type) of solar panels and battery cells at design time, such that all tasks can be executed without power shortage throughout the satellite’s mission lifetime. Second, we propose how to manage power online so as to execute the highest QoS versions of tasks (thus yielding the most power-effective performance) without compromising the power-sufficiency guarantee under a given configuration. As a case study, we study cubic-shaped nanosatellites, which have been launched multiple times since 2004. We borrow their architecture, configuration and parameters, and demonstrate the effectiveness of our design and management of satellite power systems. I