Variable speed and stop-start techniques for engine-generators

This paper presents two strategies to decrease overall specific fuel consumption (OSFC) of power generator sets (gensets), which are: variable speed and stop-start operation. In variable speed operation the internal combustion engine (ICE) is able to run in a wide range of rotational speed, therefore providing a degree of freedom to minimize the OSFC of the genset. And in stop-start operation the ICE is turned off when it is operating at low power levels where the ICE exhibit very low efficiency. When the ICE is off the energy is taken from a battery bank. After the battery state of charge decrease to predefined level, the engine is turned on charging the battery and supplying the load. The Genset consist of a Permanent Magnet Synchronous Generator (PMSG), a three phase PWM rectifier connected to the PMSG, a bidirectional boost converter allowing charge and discharge of the battery to the DC-link and a three phase 4-wires 4-legs inverter able to supply unbalanced three phase loads. Simulation results are presented to demonstrate the performance of the proposed genset.