Design and Characterization of an Actively Controlled Hybrid Energy Storage Module for High-Rate Directed Energy Applications

Abstract

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for a host of applications, including directed energy and electrical grid backup among others. Electrochemical energy storage devices, which possess either high-power density or high-energy density, have been developed recently and are very applicable for use in these applications. The need for both high energy and high power, however, makes the design and implementation of such a prime power supply a nontrivial task. While lithium-ion batteries (LIBs) are available, which possess both high power and energy density, operation at high power reduces their cycle life, decreasing the reliability and increasing the cost of the system when replacement becomes necessary more frequently. One proposed method involves optimally combining high-energy batteries with high-power electric double layer capacitors (EDLCs) using actively controlled power electronics to regulate the current to and from each respective device. In such a scheme, energy can be slowly sourced to and from the batteries, while the capacitors are used to supply or accept the bulk of the current when the demand is high, especially during fast transients. This type of scheme should not only maximize the batteries' cycle life and ensure that both the energy and power required of the load(s) is always available, but will also increase the instantaneous power capabilities of the system, offering a well-rounded solution to sourcing steady and/or transient loads. When augmenting a fossil fuel generator with a hybrid energy storage module (HESM), the HESM has the ability to act as a high-energy reservoir that can harvest energy from the generator when the loads are in short periods of inactivity. This enables the generator to be continuously base loaded, thereby maintaining a high level of efficiency at all times, while theoretically maintaining the required power quality of the main ac bus. At the University of Texas at Arlington (UTA), an actively controlled, high-rate HESM has been constructed to evaluate its performance under the typical load condition presented by directed energy weapons. It has been assembled using LIBs, EDLCs, and commercial off-the-shelf power electronic converters. A discussion about the future of HESMs, the experimental setup at UTA, and the results obtained thus far will be presented here.