A bi-directional DC-DC converter with minimum energy storage elements

Abstract

A proof-of-concept military advanced mobile generator set has been developed. The military generator set uses an internal combustion diesel engine to drive a radial-gap permanent magnet alternator at variable speed. The speed of the engine is determined from a user selectable interface that for a given load and ambient thermal conditions controls the engine to run at its most efficient operating point. The variable frequency, variable voltage produced by the permanent magnet alternator is diode-rectified to a high voltage (/spl sim/400 V) DC link, and an inverter is used to produce selectable frequency, controllable AC voltage. As part of the power electronics for this unit, a 7 kW bi-directional DC-DC converter has also been developed. The converter can charge 24 V batteries that are used to start the internal combustion engine and to power auxiliary low voltage DC loads. Additionally, the bi-directional converter can also draw power from the batteries to help maintain the high voltage DC link during severe load transients. Because of stringent weight and volume requirements for this application, the minimum in energy storage elements (high frequency transformers, capacitors, and inductors) was used. This paper presents a description and experimental analysis of this novel DC-DC converter design.