A Case for Power Management of Ship Power Systems: Improving Operational Efficiency while Maintaining Survivability and Operational Performance

摘要

Through the 20 century and up to the present day, naval ships have typically operated with an excess of generator capacity online providing redundancy to ensure that all vital systems have power in the event of a casualty. For ships with gas turbine generators, this excess capacity reduces efficiency and drives up operating costs through the consumption of fuel and increase in equipment maintenance. While it is clearly attractive to reduce the size and number of generators being used in everyday operation onboard a ship, the traditional means of reducing load in the event of a casualty - opening large numbers of breakers according to a two stage load shedding scheme that was set back at the shipyard - puts ship mission capability at risk. With increasing capability of modern ship machinery control systems, the means exists to address this risk. By configuring the power generation and distribution network online appropriately to the ship's present mission and operational conditions, and by integrating the operation of ship systems with management of electrical loads, efficiency gains and accompanying cost savings can be realized while increasing both survivability and performance. Power management entails the integration of the ship's electric plant and electrical load management with ship operations and machinery systems control as an automated control function. This concept is only just beginning to be developed for use on naval ships. Earlier efforts rely heavily on the development and use of interfaces between different supervisory control elements on the ship. Unfortunately the number and complexity of these interfaces have limited the extent to which power management has been applied, which has in turn limited the performance and efficiency gains that can be achieved. By making power management integral to the operation of any future ship machinery control system, much greater gains can be made. This paper examines the various methods in which power management can be applied - from basing the electric plant lineup on ship mission, to inhibiting the operation of individual pieces of equipment according to what portions of the electric plant are overloaded and what level of auxiliary support is needed. The paper includes a digital simulation of ship electric plant and machinery systems that analyzes the overall performance of a ship equipped with these power management capabilities in comparison with one operating with redundant generator capacity and traditional load shedding in the event of a simulated casualty.