Generation control and ED minimize the
current cost of energy production and transmission within the range
of available controls. Energy management is a supervisory layer
responsible for economically scheduling production and transmission
on a global basis and over time intervals consistent with cost
optimization.
For example, water stored in reservoirs
of hydro plants is a resource that may be more valuable in the future
and should, therefore, not be used now even though the cost of hydro
energy is currently lower than thermal generation.
The global consideration arises from
the ability to buy and sell energy through the interconnected power
system; it may be more economical to buy than to produce from plants
under direct control. Energy accounting processes transaction
information and energy measurements recorded during actual operation
as the basis of payment for energy sales and purchases.
Energy management includes the
following functions:
. System load forecast: Forecasts
system energy demand each hour for a specified forecast period of 1
to 7 days.
. Unit commitment: Determines start-up
and shut-down times for most economical operation of thermal
generating units for each hour of a specified period of 1 to 7 days.
. Fuel scheduling: Determines the most
economical choice of fuel consistent with plant requirements, fuel
purchase contracts, and stockpiled fuel.
. Hydro-thermal scheduling: Determines
the optimum schedule of thermal and hydro energy production for each
hour of a study period up to 7 days while ensuring that hydro and
thermal constraints are not violated.
. Transaction evaluation: Determines
the optimal incremental and production costs for exchange (purchase
and sale) of additional blocks of energy with neighboring companies.
. Transmission loss minimization:
Recommends controller actions to be taken in order to minimize
overall power system network losses.
. Security constrained dispatch:
Determines optimal outputs of generating units to minimize production
cost while ensuring that a network security constraint is not
violated.
. Production cost calculation:
Calculates actual and economical production costs for each generating
unit on an hourly basis.
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