Analysis and Stabilization of a Buck-Boost DC-DC Converter Feeding Constant Power Loads in Parallel with Conventional Loads in Vehicular Systems

The insertion of power electronics in vehicular technologies is becoming widespread. The increasing use of power electronic controlled 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 level 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. This paper aims to devise a novel digital technique, pulse adjustment, for damping the instabilities and ensuring orderly operation of the system. In spite of its simplicity pulse adjustment offers a very fast and smooth response. Simulation results as well as experimental outputs are presented to verify the proposed technique