The Use of Cubic Cost Curves in the Economic Loading of Electric Power Systems

This paper describes two methods for computing economic loading schedules of electric power systems in which the generator cost curves may be approximated with third-degree polynomials of the form F
_j
= A
_3j
p
_j
³
+ A
_2j
p
_j
²
+A
_1j
P
_j
+A
_0j
with constraints P
_minj
≤P
_j
≤P
_maxj
, where F
_j
is the cost of generation in dollars per hour at unit j, P
_j
is the output power in megawatts at unit j, and A
_0j
, A
_1j
, A
_2j
, A
_3j
are constants for unit j. The effect of using extrapolation or interpolation in the iterative solution of the economic loading equations is treated in detail, including the effect of changes in system loading and in the magnitude of the loss formula coefficients.