The selection of the right power distribution architecture for a given application has a tremendous impact on the overall system in terms of efficiency, cost, reliability, fault tolerance and size. Moreover, with the increasing number of power sources, storage elements, different supply voltages and strong requirements imposed at system level, the selection of the appropriate architecture becomes a nightmare for the system designer. The purpose of this paper is to describe a methodology for the selection of the most suitable architecture for a fuel cell based power distribution application. The methodology is based on the assessment of metric functions for all the components that can configure the architecture as a function of the electrical boundary conditions of each component.

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High level decision methodology for the selection of a fuel cell based power distribution architecture for an aircraft application

This thesis documents the work on the modeling of double layer capacitors (DLCs) and the validation of the modeling procedure. Several experiments were conducted to subject the device under test to a variety of charging/discharging profile and temperatures in an effort to simulate the various conditions such a device might encounter in an automotive type application. High and low current charging profiles were performed for both charge/discharge and charge/hold/discharge type experiments. Low temperature (--25 C), room temperature (-21 'C), and high temperature experiments (-50' C) were performed for the investigation of temperature effects on these devices. The derived DLC model was used in PSpice® and Matlab® simulations to determine how accurately the model could predict the performance of the device. The nonlinear characteristics of the device were also investigated and the nonlinear modeling information presented as an addition to the basic DLC model. Device variation was explored for a small sample of these devices in an effort to gain insight on the range of tolerances for modern devices. This work also presents an extensive look into the variety of electrochemical capacitor devices under investigation and in use today. An explanation of these devices and their distributed resistances and capacitance is included. This thesis gives a detailed look into the experimental setups and testing procedures used to test the devices, the simulations for the comparison, and presents the results of the comparison. Finally, this thesis documents the conclusion that this simple model procedure adequately predicts the performance of the device under these various performance profiles. Thesis Supervisor: Dr. John G. Kassakian Title: Professor and Director Laboratory for Electromag. and Elec. Sys.

Double layer capacitors : automotive applications and modeling

In this paper, a study has been performed for optimal design and development of dynamic voltage compensation system using supercapacitor to solve voltage sag which are considered the dominant disturbances affecting power quality. Supercapacitor is employed to compensate dynamically for the voltage sag of system with sensitive load. With the prolific use of semiconductor devices in electrical equipment, modern-day loads are becoming increasingly sensitive to the sags and the disturbances prove to be costly to industries. As a technology -driven custom power installation, the dynamic voltage compensation system is recognized to be most effective equipment that can be used to counter the voltage sag problem. Hence, this paper proposes the high-performance optimal design of dynamic voltage compensation system which can efficiently compensate the instantaneous voltage sag and instantaneous interruption of the utility voltage source. This DVR system consists of a dynamic voltage converter in series with the supply voltage and high-efficiency controller of energy storage device using supercapacitor. Recently, in energy storage systems, the supercapacitor is paid attention as a new environmentally friendly energy storage element. This capacitor stores higher energy density than the conventional electrolytic capacitor. Also, this capacitor has a lot of advantages such as maintenance-free, longer life cycle and faster charge-discharge time than the conventional battery system. However, the supercapacitor for dynamic voltage compensation system must have each charge-discharge controller to control, a series-parallel switching circuit to use energy effectively with application of several compensation techniques for optimal operating. Therefore, in this paper, optimal development of on-line type dynamic voltage compensation systems is proposed.

Development of on-line type dynamic voltage compensation system using supercapacitor

Electric double-layer capacitor (EDLC) is a perfect complement of battery in technical character. The EDLC/battery hybrid has the virtues of high energy density, high power density and long cycle life. The model of the hybrid was established and the performance was analyzed in this paper. In pulsed load applications, the amount of battery and system cost can be reduced largely due to the high power density of EDLC. In renewable power systems, the life of battery is prolonged and the operating cost of the whole system is reduced with most of the small charging-discharging cycles carried out by EDLC. The EDLC/battery hybrid has a nice economic effect and is valuable especially in pulsed load applications and renewable systems.

Economic analysis of EDLC/battery hybrid energy storage

Stability problems of DC Distributed Power System (DPS) arise with the widely use of tightly regulated power modules including: (i) negative impedance characteristic in small-signal sense of constant power load, (ii) the interaction among the power converters. The concept of impedance specifications for a stable DPS was introduced and explained. Electric Double-Layer Capacitor (EDLC) has high power density and small Equivalent Series Resistance (ESR). A viewpoint was brought forward originally in this paper that the output impedance of DC DPS will be reduced and system stability will be improved largely by linking EDLCs to the DC bus. It was proved valid and feasible in a design instance.

Stability study of DC DPS and the improvement with EDLC

A summary of issues impacting the application of double-layer capacitors in various military and commercial industry situations is given in this paper. The focus is on the performance parameters of the capacitors, which are the equivalent capacitance, the series resistance, and the parallel resistance, and how these parameters impact specific applications. Some discussion of the need to form banks of capacitors is also given for the different applications. The use of power conversion systems to satisfy load constraints (e.g. constant voltage) is provided due to the common need for this equipment in many of the applications.

J.E. Schatz

Papers

Characterization of double-layer capacitor application issues for commercial and military applications