An integrated electric plant control architecture for future navy surface combatants

Abstract

The emphasis by the U.S. Navy on the survivability of its warships' electric plants has prompted the investigation into unconventional control and protection systems. Working from a baseline electric plant configuration, the traditional independent control and protection systems are evaluated in light of the expected needs of the customer. In addition to survivability, these needs include requirements of reduced life cycle costs and improved performance. A bi-level distributed processing architecture is proposed consisting of load center controllers (LCCs), remote power controllers (RPCs), and two high speed communication layers. The philosophy of the architecture is to utilize the ship-wide communications network, which is essentially an Ethernet. to allow the LCCs to communicate on a peer-to-peer basis. When communication is functional, the LCCs perform system-wide control tasks in addition to their local load center protection tasks. The various tasks are allocated and performed on a prioritized basis. The priorities are assigned based on the real-time operational status of the ship and electric plant. In all cases, the local load center protection and control tasks are the highest priority of each LCC. If an LCC is too busy to perform system-wide control tasks, the task assignment algorithm either finds another LCC to perform the task, or the task goes uncompleted, depending on its priority. The LCCs do not interface with the electric plant directly, instead they each control multiple RPCs over a local communication bus. The RPCs are intelligent devices containing sensing and switching capabilities. Under normal circumstances, the RPCs handle the rapid detection and clearing of fault conditions. This frees the LCC to perform more complex tasks such as postfault system reconfiguration, incipient and high impedance fault detection, load center differential protection, load management and generation scheduling. The LCCs, RPCs, and their interaction under various conditions are described in detail. Since the LCC and RPC have not been developed, a commercial product intended for terrestrial distribution feeder monitoring is compared with the LCC and RPC specifications. This device is presently one of the most advanced systems in use. It compares favorably with the RPC and is almost acceptable as an LCC.