This project studied the use of Li-ion Energy Storage Systems (ESS) coupled with advanced phasor-based microgrid control technology to improve the economics, reliability and performance of Department of Defense (DoD) installation microgrids. A combination of techno-economic and reliability analysis was performed for conceptual energy storage enhanced microgrids at five different DoD installations. The project team considered Li-ion ESS, with sizes ranging from 100 kW to over 3000 kW, and durations ranging from 1-6 hrs of total storage. The ESS, as well as other components in the microgrid, were controlled by PXiSE’s Active Control Technology (ACT) phasor-based microgrid controls. Controller Hardware-in-the-Loop (C-HIL) testing was performed to evaluate ACT performance based upon IEEE 2030.8 Microgrid Controller Testing standard requirements. Three overarching objectives were defined to address reliability, economics, and technical feasibility of the approach. These overarching objectives served as the basis of eight detailed performance objectives that were addressed via reliability and techno-economic analysis, and C-HIL testing.

Technology Description

Li-ion batteries were chosen due to their low cost, acceptable cycle life, and versatility. These batteries were used as part of an ESS that included an inverter capable of grid-forming and dynamic transfer to ride-thru un-planned outages. When combined with appropriate switching, this can enable elimination of dedicated uninterruptible power supplies (UPS) units in favor of more cost effective multi-function ESS units.

The microgrid designs analyzed use PXiSE’s ACT high speed microgrid controls to exploit the dynamic response characteristics of the ESS and allow decoupled control of real and reactive power. PXiSE’s control improves reliability by allowing multiple grid forming ESS units that are undersized in lieu of one larger unit, and economics by allowing precise control of power at multiple points in the microgrid to simultaneously satisfy multiple value stacking objectives.

Demonstration Results

Analysis was used to determine the reliability of the proposed storage enhanced microgrid configurations at five DoD installations. C-HIL testing was used to evaluate the ability of the PXiSE ACT controls to realize control assumptions made in the reliability and techno-economic analysis. Economically optimized energy storage enabled microgrid designs were identified for all installations that could meet the required reliability. These designs reduced energy security costs ($/kW protected load) 6% to 169% through grid-tied operations, and by eliminating UPS units and diesel generators. C-HIL testing was performed with ACT controls, successfully completing 17 microgrid control and operation tests based on IEEE 2030.8 requirements.

Implementation Issues

The Phase I study concludes that short duration Li-ion energy storage can be used in a DoD installation microgrid to improve reliability with significantly reduced cost vs. an all-diesel microgrid. Techno-economic analysis showed that value stacking market participation functions is most important, followed by UPS elimination. Reliability analysis showed that 1-2 diesel generators can be cost effectively eliminated. C-HIL testing showed that PXiSE’s ACT controls can enable key functionalities assumed the techno-economic and reliability analyses regarding renewable integration, multi-ESS microgrid reliability, and value stacking.