Variable, nonlinear tie-line frequency bias for interconnected systems control

In February 1984, Union Electric began implementation of a test to identify the improvement to electric system automatic generation and tie-line control that could be achieved by the application of variable nonlinear tie-line frequency bias. Variable, nonlinear tie-line frequency bias is a better simulation of electric system frequency response than fixed straight-line bias because it recognizes the variable nature of a system's reaction to frequency changes. Important components of this response are the deadband in turbine-generator governors, variations in the number of online generators, and variations in load. The test showed that when tie-line frequency bias is better matched to system response, the result will be improved area-control error performance and reduced generating unit regulation. In addition, interconnection reliability is enhanced due to the fact that variable, nonlinear tie-line frequency bias does not inhibit the full governor response during large frequency disturbances, thereby providing better interconnected systems frequency stabilization.>