2 research outputs found

    Protection and Disturbance Mitigation of Next Generation Shipboard Power Systems

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    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

    Fault Protection Considerations for MVDC Shipboard Power Systems Operating With Pulsed-Power Loads

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    Medium Voltage Direct Current (MVDC) power distribution architectures are of immense interest for various shipboard power applications due to their advantages over classical MVAC distribution systems with respect to power quality, power density, and efficiency. However, MVDC are far away from maturity when compared to MVAC with respect to fault detection and isolation. Currently, there are no standards available for applying MVDC protection systems in shipboard applications. Furthermore, due to the absence of zero crossings in DC waveforms and unique transient fault signatures, it is challenging to design effective protection system schemes to isolate faults via conventional protection systems. This paper investigates and analyses various types of shipboard MVDC dynamic fault behaviours and signatures under different DC bus disturbances such as: bus to ground, bus to bus to ground, and impact of Pulsed-Power Load (PPL) with and without faults on a shipboard MVDC distribution system. Furthermore, 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 PPLs in MVDC systems. 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
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