Control Oriented Modeling and System Identification for a Generator Set

A diesel generator set (genset) refers to a diesel engine powered electrical alternator. Controls are needed to regulate the electrical output at the nominal voltage (120V RMS) and frequency (60Hz) despite variation in the electrical loads. In this paper, a system model for the genset is developed. A grey-box system model that considers known physical dependence and empirical identification of unknown effects is proposed. The system model structure is validated and the unknown parameters and effects are identified experimentally. Specifically, the standard proportional relationship between alternator speed and voltage is found to be valid with an experimentally determined dependence on the field current; the engine speed governor is found to be a first order controller; the effect of the back torque from the alternator on the speed dynamics is found to be consistent with the alternator and governor model. The system identification procedure is designed so that it can be easily applied to various units on the field autonomously or by a service personnel for example for tuning controllers.