Integrated Power System for Marine Applications

The increase in installed power onboard ships and the adoption of electric propulsion led to the need of a rather complex power system. The so-called Integrated Power System (IPS) feeds all the ship loads, integrating into a single entity the functions of generation, regulation, distribution and utilization of the electric power. The integration, thus being a powerful tool to increase vessel's performance, reliability and efficiency, permits also the propagation of disturbances to all the users fed by the IPS. Being Power Quality a primary need for the loads (and especially for some particular military ones) it is needed an assessment of the disturbances that can occur in the power system, both in terms of voltage and frequency transients and in terms of harmonic distortion. In this paper is presented a measurement campaign to assess disturbance levels and performance of a Naval vessel.

Incorporating a medium-voltage DC (MVDC) integrated power system is a goal for future surface combatants and submarines. In a MVDC shipboard power system, DC/DC converters are commonly employed to supply constant power to electric loads. These constant-power loads have a characteristic of negative incremental impedance, which may cause system instability during disturbances if the system is not properly controlled. This paper proposes a third-order sliding-mode controller (SMC) for DC/DC buck converters with constant-power loads. The SMC is able to stabilize the DC power systems over the entire operating range in the presence of significant variations in the load power and input voltage. The proposed SMC is validated by simulation studies in MATLAB/Simulink for stabilizing a DC/DC buck converter as well as a MVDC shipboard power system with constant-power loads for different operating conditions with significant variations in the load power and supply voltage.

The U.S. Navy recently conducted an analysis of alternatives (AOA) to set the stage for determining the characteristics and acquisition strategy for its next generation aircraft carrier. The platform design selected is expected to be in service throughout the 21st century. The parameters under consideration for change in the new carrier design lie in the areas of propulsion and electric power generation, aviation, survivability, service life, and total ownership cost (TOC) reduction. The issue of affordability is paramount This paper focuses on the need for the program management office and its supporting cost analysis staff to understand the life cycle cost (LCC) of the existing and proposed future aircraft carriers and to then translate these LCC's into meaningful information for cost‐conscious decision making. The challenge is to relate the LCC in terms the key decision‐makers and the engineering team can use to satisfy their respective roles. Thus, it is necessary to translate the results of the given ship design alternative LCC's into the paradigms of the respective stakeholders: Fleet User (operators of aircraft carriers) Ship Designers (translators of the fleet operator requirements) Program Sponsors (providers of the funding resources) Program Management Office, Shipbuilder and Supporting Industry (executors of the acquisition and construction of the ship) Navy and OSD decision‐makers (overseers of program execution) The paper describes the aircraft carrier LCC breakdown structure that has resulted, in part from a recent navy/shipbuilder integrated product team effort to capture total ownership costs. The structure has been used in the AOA as a tool to identify cost drivers and to add the time element to the cost equation in order to perform return on investment and program affordability analysis. The expanded ship work breakdown structure (ESWBS) has emerged as the central backbone of the cost work breakdown for AOA work. The ESWBS structure is a natural choice as it is the framework within which the design and engineering community works, it forms the basis of weight estimating for ships, and it has been widely used in ship acquisition cost estimating for years. In addition, the ESWBS provides perhaps the best framework from which to relate to program requirements, as it describes the ship by ship system. The approach, for the first time, provides a breakdown of the operating and support (O&S) cost elements by ESWBS. From this nucleus structure, it is possible to present costs in other required formats such as the: Office of Secretary of Defense (OSD) cost analysis improvement group (CAIG) summary level LCC categories, by ship capability or design feature, and by cost driver hierarchy.

The pulse load of an integrated power system (IPS) ship can produce very high power intermittently in a short period of time. Owing to the limited DC bus capacitance, the periodic pulse load charging and discharging process can make the IPS system state variables have a periodic alternating process during electromagnetic transients, especially at the bus voltage. In order to alleviate this problem, it is necessary to find a suitable control strategy. At first, this article establishes a mathematical model of DC bus voltage dynamics and propulsion motor load. Then, a flexible energy scheduling algorithm is proposed to coordinate the propulsion motor load and the pulse load based on the flexibility of IPS energy scheduling and the concept of virtual inertia. This algorithm can adaptively change the virtual inertia of the DC bus according to the pulse load power level and the propulsion motor load level to mitigate the impact of the pulse load on the IPS system. At the same time, the algorithm is also distributed and has little impact on the propulsion system. Finally, the effectiveness of the algorithm is verified through the mixed simulation of PSCAD and MATLAB and the hardware in the loop test.

The phrase “Multi-Power System (MPS)” refers to an application that combines different energy conversion technologies to meet a specific energy need. These integrated power systems are rapidly being lauded as essential for future decarbonized grids to achieve optimum efficiency and cost reduction. The fact that MPSs multiply several sources also multiplies their advantages to be environmentally friendly and increases the possibility of energy autonomy as they do not depend on a single source. Consequently, this increases the reliability and reduces the production costs and the size of the storage system. However, the main disadvantages of such a system are the complexity of its architecture and the difficulty in managing the power level, which leads the system to face many faults and sometimes failure. In this case, a fault-tolerant control (FTC) system can automatically adapt to component malfunctions while maintaining closed-loop system stability to achieve acceptable performance. However, on the way to build efficient FTC, one first needs to study the faults that may occur in the system in order to tolerate them. This review paper presents the faults of the MPS electrical sources used in a hybrid system, including a photovoltaic generator and a diesel generator, plus a lead–acid battery as a storage device. Only the most-encountered faults are treated.

In marine integrated power systems (IPS), dc/dc converters have been widely used to buffer the power of pulsed loads. However, limited by ship space and safety, its buffering capacity and volume are conflicting and need to be balanced. Existing methods usually oversimplify the switching dynamic process caused by the different switching periods between the pulsed loads and converters, leading to oversizing or underpowering issues of the converts. To overcome this hurdle, this article proposes a millisecond-time-scale-based state-space averaging mode (MTS-SSAM) to analyze the dynamic process by taking pulsed loads period instead of the traditional converter period as the averaging operator. Based on MTS-SSAM, taking the system allowable voltage and current fluctuation rate and converter volume as the objective function, the converters’ parameters are optimized considering the balance between buffering capacity and volume. The proposed parameters optimization method can save 49% converter volume compared with existing methods. The simulation and experimental results are presented to verify the proposed SSAM and optimization method.

ABSTRACTDuring the last five years the Naval Sea Systems Command (NAVSEA) has been studying, developing and revising design alternatives for a major class of mid‐mix surface combatants that will be operating in the surface fleet well into the 21st century. Early tasking directed that design alternatives be investigated to consider innovations, technology developments and cost reduction items while still basing the design on low risk technology. In order to fulfill these directives, comprehensive hull mechanical and electrical (HM & E) technology surveys were conducted. The purpose of these surveys was to identify and assess potential technology developments that could yield acquisition or operational cost reductions or provide significant performance improvements. R & D programs as well as developing technologies in the private sector were reviewed. Numerous trade‐off and design studies were conducted to evaluate concepts. Several of the concepts and developmental systems were incorporated into two different concept design baseline alternatives and presented to higher authority. After initial acceptance of one of the concept design alternatives the subsequent design evolved away from the more innovative concepts to a more conservative design. Many of the concepts initially incorporated into the concept design alternatives are reviewed. However, questions arise such as what risk (if any) is acceptable in the HM & E area for a new major class of ships? What can the designer do to ensure that technological developments affecting HM & E subsystems are exploited to the fullest, yet still minimize risk in the design? An attempt is made to address these questions through the design example presented.

Renewable energy sources, such as solar and wind, are attractive energy sources for the Oil & Gas industry, particularly in remote or off-shore applications. The challenge with these energy sources is that they cannot provide a steady, reliable source of energy on their own. To date, most systems rely on large battery banks or oversized generators to supplement the renewable power. The shortcomings include cost, size, weight and maintenance. Tetra West Technology has conducted a series of technical studies in order to optimize the integration of renewable energy, back-up power generation, and battery storage. These design studies have resulted in development of a system which maximizes the use of the renewable energy source, minimizing the required battery capacity, and further minimizes operating time and size of the back-up generator. Advanced integrated power management techniques can achieve 35% savings for a given solar application while assuring 99.999% power supply reliability, including remote land or off-shore locations. Integrated power management systems can be sized for a wide range of power requirements, allowing maximum benefit of renewable power – particularly when managing motor start or short term surge power requirements. These advances in power system integration are scalable and can be applied to a wide range of applications – from small remote pumping stations to large off-shore facilities. Employing components proven for these environments, an optimized integrated power management system provides a high degree of both system and power delivery reliability. With proper system sizing, these integrated systems can assure low cost and high reliability energy in a wide range of applications.

Nuclear propulsion

The difference between developed and developing societies could also be captured in the area of engineering innovations for human-center development. Engineering is one of the drivers of sustainable development in the world; it has substantial impacts on building and sustaining human capital. Nigeria, like other developing societies, is confronted with challenges of utilizing human resources maximally for her national development. Hence, this paper investigates engineering and human capacity building as the flexibility of innovation in human capital development in Nigeria. This study applied a theoretical method; information was sourced through secondary means like content analysis journals, textbooks, and electronic resources. This study anchor on modernization, human capital, and scientific management theories. Findings showed that apart from the purely academic angle, Nigeria has no made outstanding progress in the area of training and institutional support. The paper recommends broad-based engineering applications in every facet of human capital. This will attract foreign investors to the economy, and the local ones can use their technical skills to ensure maximum utilization of resources through engineering techniques. As the World Federation of Engineers is sustaining pressures on the engineering body among the member states. Nigeria cannot afford to be isolated in the area of sound engineering training. This paper will be useful to the International Labour Organisation, World Federation of Engineers, ministries of employment and capacity development, National Directorates of Employment, the Nigerian Consultative Council and researchers in the field of Human Resources and engineering management could initiate research from here.

The maintenance and service support of carrier aircraft (MSSCA) is a complex process involving many types of resources and activities that require optimisation which can be considered as a multi-resource constrained multi-project scheduling problem (MRCMPSP). It is of great significance to optimize the makespan and obtain a proactive robust schedule to be adaptive to the changes in the dynamic flight deck environment. This paper develops a critical chain method (CCM) for carrier aircraft support robust scheduling in a time-critical and resource-constrained operation environment. The CCM consists of developing a desirable deterministic schedule under multi resource constraints and time-critical issues, and adding a project buffer (PB) to the end of the schedule is used to get a robust proactive scheduling and deal with uncertainty. The triangular fuzzy number (TFN) is applied to describe the durations of each activities and calculate the PB size and obtain an appropriate proportionality between the activity duration and the buffer size. In the numerical research, different size simulations are designed to calculated the robust optimization scheduling. The computational results show that the CMM for carrier aircraft support robust scheduling can make a better decision in the robust proactive optimization scheduling about the resource allocation.

The maintenance system based on Condition-Based Maintenance(CBM) is a complex dynamic system.The interaction between the different elements leads to dynamic changes in the maintenance system.By analyzing the nature of condition-based maintenance,taking the carrier-based aircraft readiness as the research target,using the method of System Dynamics(SD),and the simulation software VENSIM special to analyze the feedback control structure of internal elements in the condition-based carrier aircraft maintenance support system,the SD model based on the condition-based maintenance for operational readiness of the carrier-based aircraft was established.The simulation results operated by the SD model show that the condition-based maintenance method introduced into the carrier aircraft maintenance support system can effectively improve the carrier aircraft's operational readiness.

This PEA was developed in compliance with USAFs Environmental Impact Analysis Process in support of the current training and maintenance activities and the development, use, and maintenance of additional military training areas on Kirtland AFB. The types of military training conducted on Kirtland AFB are common military activities that include the use of firing ranges for live weapons training and weapons qualification the use of training areas for maneuvers, force on-force rescue, real-world deployment, land navigation, convoy movement and protection, rotary-wing aircraft operations, and explosives training helicopter landing zones and the Auxiliary Helicopter Training Field for helicopter pilot training, personnel insertionextraction, and crash rescue field training exercises and Isleta drop zone for C-130 aerial delivery training. Training activities can include the use of munitions, Multiple Integrated Laser Engagement System, pyrotechnics, ground burst simulators, smokes, and flares. The Proposed Action is to continue current military training activities on Kirtland AFB, as well as provide suitable training areas on the installation, where possible, to better support Department of Defense training requirements. It is anticipated that mission requirements will continue to grow and new military training areas would be needed for conventional tactical training in dry, mountainous areas such as those found on Kirtland AFB. Further, evaluation of existing training areas for new activities and the creation of new training areas, where possible, on the installation could allow a limited amount of the off-installation activities to be brought back onto Kirtland AFB.

Metal hydride hydrogen compressors: Current developments & early markets

The cumbersome nature of wired interfaces often limits the range of application of virtual environments. In this paper, we discuss the design and implementation of a novel system, called ALIVE, which allows unencumbered full-body interaction between a human participant and a rich graphical world inhabited by autonomous agents. Based on results obtained with thousands of users, the paper argues that this kind of system can provide more complex and very different experiences than traditional virtual reality systems. The ALIVE system significantly broadens the range of potential applications of virtual reality systems: in particular, the paper discusses novel applications in the area of training and teaching, entertainment, and digital assistants or interface agents. We give an overview of the methods used in the implementation of the existing ALIVE systems.