| Abstract | A short-term economic scheduling and automatic dispatching scheme is developed in the study , to obtain optima l unit
commitment schedules and implement real time economic dispatch , for application to a basically hydroelectric power system with cascaded plants subject to water transport time delays, thermal generation providing back-up, and interchange tie -.lines where
power may be exported or imported. The scheme starts with the calculation of optimal schedules of the generating sources that will supply the expected requirement s of the system over a day or a week , with the objective of achieving proper water usage and
minimum fuel input. Real time economic dispatch tallows, which adjusts the actual loadings of the gene rating sources making them
approach to their schedules, thus implementing the annual
projection of water releases and fuel usage.
The Optimal Unit Commitment problem formulation operates
the cascaded plant storages with significant pondages as
reservoirs, a nd adjusts their storage trajectories, to obtain
optimum discharges and corresponding hydrogen rations over a scheduling interval. The terminal conditions of reservoir
storage trajectories are specified from a separate long-term unit
commitment study . optimization is performed with the Progressive
Optimality Algorithm , developed by Howson and Sancho (38) .
Deficits in hydrogeneration are supplied by thermal back-up
units . Total system transmission losses a r e considered. In
particular, the socio-economic constraints , which curtail the
generation of firm hydro power, are given explicit treatment.
Discharge and spillage time - flow profiles are developed to
account for the delays of water discharged and spilled.
Reservoir operating curves are utilized. to determine the maximum storages available from pondages.
Economic Dispatch is implemented as a main real time
algorithm , which periodically allocates economic loadings to
generating sources, and as a separate instantaneous algorithm performed in an automatic generation control scheme. The
Economic Dispatch problem formulation is based on the
coordination equations , first derived by Kirchmayer and Stagg (52) to dispatch thermal. units . The hydroelectric sources are dispatched as if they are thermal unit s , after water worth values of water in these sources are established. Two methods to calculate water worth values of water in any plant , that preserve
coordination of a cascaded system , are formulated .
The periodic and instantaneous economic dispatch loadings,
whichever is the La test, are used as economic base settings in which deviations are made to satisfy the requirements of system frequency a nd interchange. The results are desired power generations of sources under on-line control, which are made up
of both economic and regulation components. These desired powers are then transmitted to the generating sources. This process is implemented on-Line by an Automatic Generation Control scheme, that satisfies both Economic Dispatch and Load Frequency Control,
on a dedicated process control computer. To meet unexpected and abrupt load changes, an algorithm to monitor instantaneous system
spinning reserve is devised .
A computer control time frame is established for the on-line control of the system. The real time optimizing and
on-line control algorithms are performed , through activation by the program scheduler, according to the time frame . Provisions are made so that a program execution may be initiated by the dispatcher through t ask interrupt commands. To achieve
flexibility in the on-line control of the generating sources,
machine control status are established which can be appropriately assigned .
The models are applied to the Mind a n a o Power Grid of the
National Power Corporation, Mindanao Regional Center . The grid
will eventually operate seven cascaded plants of the Agus River Hydroelectric Power Complex , six cascaded plants of the Pulangui River Power Complex , cascaded and non-cascaded plants of the
Tagoloan and Cagayan Rivers, wood-fired steam generating plants, and geothermal plants a Long with the existing diesel power plant which provides the present thermal back-up. Preparation of data
in the application of the models a nd results from computer
program runs are presented. |