Page 36 - Mathematical Models and Algorithms for Power System Optimization

26 Chapter 2

(1) The generated output constraint specified for the power plant shall be compatible with
the sum of generated output of all units of the plant, namely, only if there is an intersection
with the sum of generated output of all units of the plant in any time, then the specified
constraints are reasonable.
For instance, the specified range of total generated output for a certain power plant is
assumed to be [200MW, 550MW], for which the reasonability only happens in the first
three situations, except the last one as follows:
1. If the sums of upper and lower limits of the generated output for all plant units in
various time periods are both within the specified range of the generated output for the
power plant, such as [250MW, 500MW], then the specified range is reasonable,
shown in Fig. 2.3.

The sum of lower output The sum of upper output
limits of units limits of units

Lower output limit of power plant Upper output limit of power plant
Fig. 2.3
Reasonable range 1 of power plant output.

2. If the sums of upper limits of generated output for all units of the plant in various time
periods is within the specified range for the power plant, yet the sum of lower output
limits of all units of the plant in various time periods is smaller than the lower limit of
the specified range, such as [100MW, 300MW], the specified range is also
reasonable, as shown in Fig. 2.4.

The sum of lower output The sum of upper output
limits of units limits of units

Lower output limit of power plant Upper output limit of power plant
Fig. 2.4
Reasonable range 2 of power plant output.