BASE POINT AND PARTICIPATION FACTORS
Ø This method assumes that the economic dispatch problem has to be solved repeatedly by moving the generators from one economically optimum schedule to another as the load changes by a reasonably small amount.
Ø We start from a given schedule-the base point.
Next, the scheduler assumes a load change and investigates how much each generating unit needs to be moved (i.e.,“participate” in the load change) in order that the new load be served at the most economic operating point.
Ø Assume that both the first and second derivatives in the cost versus power output function are available (Le., both F; and Fy exist). The incremental cost curve of ith unit given in the fig.
Ø As the unit load is changed by an amount, the
(13) This is true for each of the N units on the system, so that
The total change in generation (=change in total system demand) is, of course, the sum of the individual unit changes. Let Pd be the total demand on the generators (where Pload+Ploss&), then
The earlier equation, 15, can be used to find the participation factor for each unit as follows
Ø The computer implementation of such a scheme of economic dispatch is straightforward.
Ø It might be done by provision of tables of the values of FY as a function of the load levels and devising a simple scheme to take the existing load plus the projected increase to look up these data and compute the factors.
Ø Somewhat less elegant scheme to provide participation factors would involve a repeat economic dispatch calculation at.
Ø The base-point economic generation values are then subtracted from the new economic generation values and the difference divided to provide the participation factors.
Ø This scheme works well in computer implementations where the execution time for the economic dispatch is short and will always give consistent answers when units reach limits, pass through break points on piecewise linear incremental cost functions, or have non convex cost curves.