Aging transmission and substation infrastructure linking military bases to commercial utility power supplies coupled with the aging distribution system inside the base threatens mission readiness to execute training and deployment. Traditionally, the practice of providing critical facility (facilities deemed to be critical or containing critical operations or personnel) power contingency has been to install building-dedicated engine generators. However, it has been shown that the presence of these units provides a false sense of security because actual reliability is reduced due to sub-optimal and intermittent loading, inconsistent or nonexistent O&M practices, and age. A major energy challenge for military installations is to elevate their level of energy security while conforming to Assistant Chief of Staff for Installation Management requirements which mandates reduced economic and environmental impact of installation energy.This report provides a technical explanation of the power electronic and control response challenges associated with the design and analysis of an autonomous military installation scalable power system capable of operating independently from the commercial grid for extended periods of time in an emergency. This will be done by networking existing emergency backup generators and future DERs into a micro grid, largely using existing power distribution lines. The micro grid will have the ability to dynamically reconfigure itself to recover from attack, natural disaster, or network component failures (self-healing). The power provided by the micro grid will degrade gracefully after a major commercial outage, as opposed to a catastrophic loss of power, allowing more of the installation to continue operations. Rather than providing power only to predetermined mission essential facilities, the micro grid will give the mission commander the ability to dynamically designate and prioritize which facilities receive available power. The networked system of DERs and switchgear will improve energy reliability and tie it to mission readiness. Implementing a scalable power grid will assure significant enhancement of mission readiness, and as a direct consequence, intelligent system control will enable base personnel to quantify the state of mission readiness.

The deployment of microgrid technology to United States Army operations will improve energy efficiency and security. Microgrids provide fixed Army installations with the ability to "island" from the commercial power grid and operate independently for an extended period. The technology aids installations in meeting energy mandates and policy goals. Projects are already underway to demonstrate the microgrid concept at domestic installations. Several of these projects are discussed.

In the early spring of 1997, a 900-kVA, utility-tied photovoltaic power station was installed at the U.S. Army Yuma Proving Ground (YPG), in the southwest corner of Arizona (see Fig. 1). The system will be used to offset peak demand and serve as an emergency power system for YPG's water treatment plant. The power station includes 450-kWp of Siemens M-55 modules, 5600-kWh of C&D motive power batteries (see Fig. 2), and a 900-kVA power processing (see Fig. 3) and control system from Trace Technologies. Enhanced by the battery load leveling system, the power station has the capacity to reliably provide from 450-up to 825-kVA to YPG's utility grid during the summer peak demand season. The YPG system has three basic operating modes: (1) daytime utility-tied, (2) nighttime utility-tied, and (3) stand-alone.

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