Operation characteristics of isotropic synchronous generators connected to a stand-alone DC system

The operation of a synchronous generator connected to a dc load by a six-pulse diode bridge is analyzed in this paper. The dc load has in parallel a high electrolytic capacitor to reduce the ripple in the dc voltage: the dc voltage is regulated acting on the field current of the generator. Such a layout is currently used to create a stable and reliable dc-bus for stand-alone dc systems as in electro-diesel locomotives or ships. Due to the presence of bulk capacitors, the dc side can be considered a voltage source rather than a current source, and the ac voltage across the generator as well as the stator current are considerably distorted. By using simulations based on a dynamical model of the generator, the paper shows the most significant operation modes of the system and gives some insight into the power transfer as well the impact of the harmonics for the design of the generator.