Speed control with incremental algorithm of minimum fuel consumption tracking for variable speed diesel generator

This paper presents a model of a diesel-combustion-engine-based variable speed generation unit driving a permanent magnet generator loaded by a power converter. Variable speed operation of the internal combustion engine facilitates fuel saving when the load profile changes, but it requires a power conditioning unit such as an electronic converter. Power converter operation is well known from wind energy conversion systems, in which variable speed operation increases their efficiency. The paper presents modeling and speed control of an exemplary diesel engine, and control of output voltage and current of the power electronics converter loading the generator. Special attention has been paid to elaboration of the methods of minimum specific fuel consumption points tracking for the given load. Incremental algorithms can find minimum specific fuel consumption in the case in which the details of fuel consumption curves are not exactly known. The incremental algorithm has been adopted from wind energy conversion systems and partly modified to avoid torque peaks during incremental step changes of reference speed. The concept has been validated in a simulation using data of a real model of an internal combustion engine through a three-dimensional approximation of fuel consumption characteristics.