Frequency security constrained short-term unit commitment

In island grids and weakly interconnected power systems, a loss of a large proportion of generation will cause the system frequency to fall dramatically. In order to ensure a stable operation with the lowest impact on the system, the disturbed power balance must be equalized within a short specified time by activating the seconds reserve of on-line units or by load shedding or both. This paper presents a frequency security constrained short-term scheduling. The procedure commits and optimizes units, calculates necessary seconds reserve capability, and allocates them among the available on-line units to provide emergent frequency regulation following a loss of generation. By means of the low-pressure pre-heater interruption (LPHI) implemented into thermal power plants, seconds reverse provision is increased. Thus, load shedding caused by insufficient availability of seconds reserve can be avoided. A case study on typical island systems with a large number of different units is demonstrated using the proposed procedure. Results from the study validated robust performance of the proposed procedure that minimizes fuel costs while maintaining frequency security condition. (C) 2002 Elsevier Science B.V. All rights reserved.