Recreating the mechanical response of a diesel generator set using a variable speed DC drive

With the introduction of emissions legislation to industrial engines, along with customer expectation of increased power density and decreased steady-state fuel consumption, modern diesel engines are experiencing less favourable transient performance when subjected to a step increase in load. When a DC motor driven alternator is used for laboratory tests the transient speed deviations are considerably smaller. Since the electrical characteristics of a DC motor allow for a fast torque response when experiencing an increased mechanical load, the varying frequency effect observed on the output voltage is not normally experienced in a laboratory scenario. This paper describes a method of recreating the mechanical response during load acceptance on a diesel gen-set when using a dc motor driven alternator. The motorpsilas speed is controlled by a variable speed drive with the use of a diesel engine model. Results have been included to provide a comparison between the DC motor driven alternator, the model and a real generator set.