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As part of the U.S. Navy’s continued commitment to protecting U.S. interests at home and abroad, the Navy is investing in the development of new technologies that broaden U.S. warship capabilities and maintain U.S. naval superiority. NAVSEA is developing power systems technologies for the Navy to realize an all-electric warship. New nonlinear power system controls approaches are being developed to improve system performance in light of new electrically powered weaponry that behave as pulsed-loads. Advancements include the identification of pulsed-load profiles that identify Energy Storage System (ESS) requirements. A dynamic optimization engine has been developed and serves as the feedforward receding horizon control portion of the Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) feedback controls for ESS networked microgrid system. A Coalition Warfare Program (CWP) test scenario was selected. The CWP is defined with a Reduced Order Model (ROM) that includes; generation, ESS, and mission pulsed-loads. Several numerical simulation studies were conducted. The CWP scenario is bounded by a baseline mission load local ESS contrasted with no ESS full nonlinear metastable boundaries. The main goal is to minimize ESS size and weight while maintaining power system performance. This paper focuses on the control and optimization of ESS as an integral part of supporting critical mission loads and real-time control algorithm development to improve future energy efficiency for multi-mission activities.&nbsp

Many candidate power system architectures are being evaluated for the Navy’s next generation all-electric warship. One proposed power system concept involves the use of dual-wound generators to power both the Port and Starboard side buses using different 3-phase sets from the same machine (Doerry, 2015). This offers the benefit of improved efficiency through reduced engine light-loading and improved dispatch flexibility, but the approach couples the two busses through a common generator, making one bus vulnerable to faults and other dynamic events on the other bus. Thus, understanding the dynamics of cross-bus coupling is imperative to the successful implementation of a dual-wound generator system. In (Rashkin, 2017), a kilowatt-scale system was analysed that considered the use of a dual-wound permanent magnet machine, two passive rectifiers, and two DC buses with resistive loads. For this system, dc voltage variation on one bus was evaluated in the time domain as a function of load changes on the other bus. Therein, substantive cross-bus coupling was demonstrated in simulation and hardware experiments. The voltage disturbances were attributed to electromechanical (i.e. speed disturbances) as well as electromagnetic coupling mechanisms. In this work, a 25 MVA dual-wound generator was considered, and active rectifier models were implemented in Matlab both using average value modelling and switching (space vector modulation) simulation models. The frequency dynamics of the system between the load on one side and the dc voltage on the other side was studied. The coupling is depicted in the frequency domain as a transfer function with amplitude and phase and is shown to have distinct characteristics (i.e. frequency regimes) associated with physical coupling mechanisms such as electromechanical and electromagnetic coupling as well as response characteristics associated with control action by the active rectifiers. In addition, based on requirements outlined in draft Military Standard 1399-MVDC, an approach to derive specifications will be discussed and presented. This method will aid in quantifying the allowable coupling of energy from one bus to another in various frequency regimes as a function of other power system parameters. Finally, design and control strategies will be discussed to mitigate cross-bus coupling. The findings of this work will inform the design, control, and operation of future naval warship power systems.

As part of the U.S. Navy’s continued commitment to protecting U.S. interests at home and abroad, the Navy is investing in the development of new technologies that broaden U.S. warship capabilities and maintain U.S. naval superiority. In particular, NAVSEA is supporting the development of power systems technologies that help the Navy realize an all-electric warship. It is recognized that a challenge to fielding an all-electric power system architecture includes minimizing the size of energy storage systems while maintaining the response times necessary to support potential pulsed loads. This work explores the trade-off between energy storage requirements (i.e. size and weight) and performance (i.e. bandwidth and storage) in the context of a power system architecture that meets the needs of the US Navy. To compare energy storage technologies and appropriately size them, it is necessary to specify size and weight requirements and thus consider the energy density of the technology in Wh/kg and specific power density in W/kg. The modelled time domain behaviour for different load types and control delays were used to determine technology and sizing requirements by comparing the total energy and maximum power used in the simulation to a Ragone plot. Simulation results based on operational vignettes were used to identify a range of specific power and energy densities that will meet system requirements. Potential energy storage sizing can be determined by approximating where a selected technology intersects with the energy and power requirements of the system. Another major component necessary to determine energy storage technology is the frequency domain behaviour of the system. In this work, the energy storage control bandwidth is evaluated in simulation for different loading scenarios, and a trade-off between size/weight and response bandwidth is illustrated.&nbsp

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