Study of effectiveness of under-excitation limiter in dynamic modeling of Diesel Generators

The Under Excitation Limiter (UEL) has been introduced in the excitation systems mostly to prevent the loss of synchronism of generators and also prevent exceeding machine under-excited capability limit which otherwise leads to overheating of the stator of the machine and also challenges different part of generator protection and control system. In this paper, its effect on the modeling of Diesel Generator´s excitation system during island operation (i.e. local network) is studied. The simulation results performed in the Matlab/Simulink using IEEE type ST2A excitation model suggests that in the local network with mainly inductive loads the UEL is ineffective and it can be neglected in the modeling.