Suitability of the pulse adjustment technique to control single DC/DC choppers feeding vehicular constant power loads in parallel with conventional loads

Abstract

The increasing use of power electronic and motor drives in land vehicles, marine vessels and aircraft, for lots of applications such as propulsion, braking, steering, and actuation is creating particular problems when the power distribution system is in the form of multi-converter dc electrical systems. This is because of many power electronic loads and associated controllers which have a 'constant power' characteristic resulting in negative incremental input impedance. The effect of such loads in a dc system is to cause instability. The purpose of this paper is first to identify the most appropriate theoretical techniques for analysis of this nonlinear instability, and then to devise a novel technique for damping the instabilities and ensuring stable operation of system. We call this new control technique, Pulse Adjustment. In spite of its simplicity it offers a very fast and smooth response. Simulation and experimental results are presented to verify the proposed technique.