Control systems analysis of industrial plants with synchronous generators during islanded operation

This work presents a methodology that permits to show, in a graph, the maximum allowable time for changing the distributed synchronous generator excitation system and speed governor control modes after the occurrence of an islanding, for a wide range of values of power unbalances between load and generation. The visualization of this parameter becomes interesting when the conflict between the synchronous generator control modes for grid connection operation (parallel) and for islanding operation is taken into account. At the point of view of practical implementation, this time is desirable to be sufficiently high, so that the decision of altering the control mode does not result in a false detection of an islanding situation. From another perspective, changing the generator control mode needs to be sufficiently fast in order to avoid the operation of voltage and frequency relays used in the generator protection.