Shipboard condition based maintenance and integrated power system initiatives

Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 80-81).With the U.S. Navy's continued focus on developing and implementing a robust integrated power system aboard future combatants, there has been an ever increasing effort to guarantee an electrical distribution system that maintains maximum capabilities in the event of a system fault. It is believed that the implementation of a device such as a non-intrusive load monitor (NILM) can greatly assist in the preemptive detection of such faults and failures. Ongoing NILM research conducted at Massachusetts Institute of Technology's Laboratory for Electromagnetic and Electronic Systems (LEES) is exploring the application of NILM technology in shipboard environments. The NILM's unique ability to the monitor the power usage profile of these systems can be used to immediately diagnose system casualties and unusual operation parameters. Additionally, research has shown that the NILM can be used effectively and reliably, to monitor equipment health, recognize and indicate abnormal operating conditions and casualties and provide invaluable information for training operators, diagnosing problems and troubleshooting. This thesis will discuss how this frequency content of the aggregate measurement can be used to assess the health of motors. Experiments were conducted in the confines of LESS in addition to aboard USCGC ESCANABA (WMEC-907), a 270-foot Coast Guard Cutter, in order to better understand the system dynamics in a real life environment. To further support the US Navy's integrated power system initiatives two hardware models of a shipboard electrical propulsion drive system were constructed, an MVDC propulsion simulation and a doubly-fed machine propulsion model. These simulations were built for the purpose of testing innovative integrated propulsion system theories, algorithms, configurations and new electric propulsion concepts.by Darrin E. Barber.S.M.Nav.E

Asynchronized Synchronous Motor-Based More Electric Ship-Less Power Electronics for More System Reliability

© 2019 IEEE. Nowadays, the fully power decoupled shipboard power system (SPS) architecture is popular. However, the volume of fragile power electronic converters is large, and the system overload capability is low. In this paper, an asynchronized synchronous motor (ASM)-based SPS is proposed for more-electric ships to handle these issues. The models of the simplified synchronous generator (SSG), ASM, back-to-back converter, and supercapacitor bank are established. Besides, the transfer function of the SSG excitation system is obtained, with the SSG stability analyzed. Moreover, an ASM control strategy based on the emulated stator voltage orientation (ESVO) without the phase-locked loop is proposed to control the ASM. By using the proposed ESVO scheme, the impacts on electric machines are mitigated by the effective SSG stator power control and ASM torque control. High quality of the three-phase voltage and current waveforms can also be obtained. Furthermore, the simulation study is carried out in MATLAB/Simulink to verify the performance of the proposed ASM-SPS. The proposed ESVO scheme and the conventional stator-flux-oriented control strategy are implemented, and the operation of an induction-motor-based SPS with grid voltage orientation is also illustrated for comparison, with frequent propulsion load variations taken into consideration

Battery Sources and Power Converters Interface in Waterborne Transport Applications

In recent years the electrification in the waterborne transport application is in noticeable development. To face the high battery cost, a proper design of the energy storage system is required. For battery sources, the solution worthy of investigation is the use of a hybrid energy storage system (HESS). HESS is composed of a power-dense battery and an energy-dense battery. The use of a HESS allows better optimization of the energy and power levels of the energy storage system. In the paper, the battery source requirements in the waterborne transport application are evaluated to achieve the best trade-off among energy, maximum power, and life cycle. Furthermore, the power converters selection, to balance the power flow among the batteries and the vessel electrical network is described

Protection and Disturbance Mitigation of Next Generation Shipboard Power Systems

Today, thanks to modern advances mainly in the power electronics field, megawatt-level electric drives and magnetic levitation are being integrated into the marine power grids. These technologies operate based on Direct Current (DC) power which require Alternating Current (AC) to DC conversion within the current grid. Medium-voltage Direct Current (MVDC) and Flywheel Energy Storage Systems (FESS) are the next state-of-the-art technologies that researchers are leaning on to produce, convert, store, and distribute power with improved power quality, reliability, and flexibility. On the other hand, with the extensive integration of high-frequency power electronic converters, system stability analysis and the true system dynamic behaviors assessment following grid disturbances have become a serious concern for system control designs and protection. This dissertation first explores emerging shipboard power distribution topologies such as MVDC networks and FESS operation with charge and discharge dynamics. Furthermore, the important topic of how these systems perform in dynamic conditions with pulsed power load, faults, arc fault and system protection are studied. Secondly, a communication-based fault detection and isolation system controller that improves upon a directional AC overcurrent relay protection system is proposed offering additional protection discrimination between faults and pulsed-power Load (PPL) in MVDC systems. The controller is designed to segregate between system dynamic short-circuit fault and bus current disturbances due to a PPL. Finally, to validate the effectiveness of the proposed protection controller, different bus current disturbances are simulated within a time-domain electromagnetic transient simulation of a shipboard power system including a PPL system operating with different ramp rate profiles, pulse widths, peak powers, and fault locations. This overarching goal of this work is to address some of the critical issues facing the US Navy as warfighter mission requirements increase exponentially and move towards advanced and sophisticated pulsed power load devices such as high energy weapon systems, high energy sensor and radar systems. The analyses and proposed solutions in this dissertation support current shipbuilding industry priorities to improve shipboard power system reliability and de-risk the integration of new power system technologies for next generation naval vessels

Research on Multi-Energy Integrated Ship Energy Management System Based on Hierarchical Control Collaborative Optimization Strategy

The propulsion systems of hybrid electric ship output and load demand have substantial volatility and uncertainty, so a hierarchical collaborative control energy management scheme of the ship propulsion system is proposed in this paper. In a layer of control scheme, the traditional perturbation algorithm is improved. Increasing the oscillation detection mechanism and establishing the dynamic disturbance step length realizes the real-time stability of maximum power point tracking control. In the second-layer control scheme, the power sensitivity factor and voltage and current double closed-loop controller is introduced. By designing a two-layer coordinated control strategy based on the dynamic droop coefficient, the problem of voltage and frequency deviation caused by load switching is solved. In the third-layer control scheme, due to the need of the optimal scheduling function, the multi-objective particle swarm optimization algorithm was improved through three aspects: introducing the mutation factor, improving the speed formula, and re-initializing the strategy. Compared with other algorithms, this algorithm proves its validity in day-ahead optimal scheduling strategy. The superiority of the hierarchical collaborative optimization control schemes proposed was verified, in which power loss was reduced by 39.3%, the overall tracking time was prolonged by 15.4%, and the environmental cost of the diesel generator was reduced by 8.4%. The control strategy solves the problems of the steady-state oscillation stage and deviation from the tracking direction, which can effectively suppress voltage and frequency fluctuations

Hybrid power-system architecture for micro-grid

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 77-79).Load-independent, fixed-speed operation of prime-movers, such as gas turbines and diesel engines, leads to degraded efficiency at part-loaded conditions. This thesis looks at a hybrid power-system architecture that can boost fuel economy through coordinated variable-speed operation of both prime-movers and drive loads. The propulsion plant of an electric ship serves as an example of a micro-grid with a focus on efficiency and dynamic performance. The proposed power distribution system employs doubly-fed machines for generation and for variable speed loads, and can be used where variable-speed operation improves prime-mover efficiency while minimizing required power electronics ratings. The hybrid power-system architecture achieves reduced fuel footprint, less weight and volume constraints by minimizing system power-electronics rating and allows for a selection of an optimum prime-mover.by Shibal Ibrahim.S.M

Dynamic Reactive Power Control of Isolated Power Systems

This dissertation presents dynamic reactive power control of isolated power systems. Isolated systems include MicroGrids in islanded mode, shipboard power systems operating offshore, or any other power system operating in islanded mode intentionally or due to a fault. Isolated power systems experience fast transients due to lack of an infinite bus capable of dictating the voltage and frequency reference. This dissertation only focuses on reactive control of islanded MicroGrids and AC/DC shipboard power systems. The problem is tackled using a Model Predictive Control (MPC) method, which uses a simplified model of the system to predict the voltage behavior of the system in future. The MPC method minimizes the voltage deviation of the predicted bus voltage; therefore, it is inherently robust and stable. In other words, this method can easily predict the behavior of the system and take necessary control actions to avoid instability. Further, this method is capable of reaching a smooth voltage profile and rejecting possible disturbances in the system. The studied MicroGrids in this dissertation integrate intermittent distributed energy resources such as wind and solar generators. These non-dispatchable sources add to the uncertainty of the system and make voltage and reactive control more challenging. The model predictive controller uses the capability of these sources and coordinates them dynamically to achieve the voltage goals of the controller. The MPC controller is implemented online in a closed control loop, which means it is self-correcting with the feedback it receives from the system