Page 74 - Mathematical Models and Algorithms for Power System Optimization

64 Chapter 3

Fig. 3.7
Fuzzy membership function curve of manpower constraint.

3.5 Expert System Developed for GMS

The expert rules are well defined so that the linguistic rules can be expressed as a mathematical
set or logical expression, and can be input by the user into the GMS program. Based on the
system requirements for GMS and the experience of the dispatch engineers, the generalized ES,
which is abstracted from reasoning rules, can be constructed.
The GMS ES knowledge base could be constructed based on the actual requirements of the
system and the GMS scheduling experience of the power grid dispatchers. The GMS ES
consists of several abstract reasoning rules and can be used to optimize, accelerate, and
standardize the GMS solution procedure.
Some special factors considered in this GMS are explained in detail as follows.

3.5.1 Selecting of Time Units

Prior to the GMS, a proper time unit shall be selected. A shorter time unit will increase the
computation time but make the maintenance combination more flexible; a longer time unit will
make the GMS inflexible but decrease the computation time. Hence, various factors should be
comprehensively considered for selecting the time unit.

At present, the GMS of all power grid dispatching departments may be roughly divided into
annually, quarterly, and monthly plans. The system will often suffer from unexpected changes
in conditions, which inevitably prevents the annually and quarterly plans from precise
execution. Thus, such plans may be somewhat rough, and their time units may be measured in
weeks. However, the monthly GMS is generally a real one that must be executed, so the time
unit of that one should be accurately set as a day.