Electrical Power Systems

Optimal System Operation
16.1 INTRODUCTION
Optimal System Operation 405
16
The efficient and optimum economic operation and planning of electric power generation
systems have occupied an important position in the electric power industry. The efficient use of
the available fuel is growing in importance, both monetarily and because most of the fuel used
represents irreplaceable natural resources. A savings in the operation of generating systems of
a small percent represents a significant reduction in operating cost as well as in the quantities
of fuel consumed. The optimum operation of the system involves the consideration of economy
of operation, system security, emissions at certain fossil-fuel plants. The hydrothermal
coordination problem is another optimum operating problem area that has received a great deal
of attention. Another factor that influence the power generation at minimum cost is transmission
losses. The most efficient generator in the system does not guarantee minimum cost as it may
be located in an area where fuel cost is high. Also, if the plant is located far from the load center,
transmission loss may be higher and hence the plant may be uneconomical. Therefore, the
basic objective is to determine the generation of different plants such that total operating cost
is minimum. The operating cost plays an important role in the economic scheduling.
16.2 ORMULATION O THE ECONOMIC DISPATCH PROBLEM
The total cost of operation of generators includes fuel, labour, and maintenance cost but for
simplicity only variable costs need to consider are fuel costs. The fuel cost is important for
thermal and nuclear power plants. or the fuel costs, it is assumed that fuel-cost curves for each
generating unit is given. The fuel cost curve of a generating unit specifies the input energy rate
i (P gi ), [MKCal/hr] or cost of fuel used per hour C i (P gi ) [Rs/hr] as function of the generator
power output P gi. This curve can be obtained experimentally. or simplicity, it is assumed that
each generating unit consists of a generator, turbine, steam generating unit (boiler furnace),
and associated auxilliary equipment. An approximation of fuel cost curve is shown in ig. 16.1.
ig. 16.1: uel cost curve.