Transmission Expansion Planning in Deregulated Power ... - tuprints

3 Probabilistic locational Marginal Prices 28
LMP of bus No. 1 in $/MWhr
35
30
25
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5
0
0 500 1000
Monte Carlo iteration
1500 2000
0
0 500 1000
Monte Carlo iteration
1500 2000
(a)
(b)
Fig. 3.5- LMPs of buses 1 and 2 in different iteration of Monte Carlo simulation
congestion, input power of the tie-line TL2 which behaves as a zero bid generator prevents
from dispatching cheap generation near bus 2. This is why the LMP of bus 2 is zero in some
operating points (see figures 3.4.(b) and 3.5.(b)). If there is transmission congestion between
buses 2 and 4, the output power of tie-line TL4 is provided by the generators which are
located near bus 4. These generators have high bids. Therefore, this wheeling transaction
causes expensive generation dispatch instead of cheap generation. This example shows that
wheeling transactions affect the LMPs of control areas that transmit through them.
In above example the wheeling power is in the direction of network congestion and increase
the intensity of congestion. Now suppose the direction of wheeling changes. Figure 3.6 shows
mean of generation power, mean of load, mean of power of lines, and mean of LMPs for
wheeling from bus 4 to bus 2. Comparison of figure 3.6 and 3.3 shows if direction of
wheeling power changes, the wheeling power decrease the congestion and release
transmission capacity. PDFs of power of lines 2 and 6 are shown in figure 3.7. Comparing
figures 3.7.a and 3.7.b shows that if direction of wheeling power changes, the probability of
congesting line 2 decreases from 0.875 to 0.194. The probability of congesting line 6
decreases from 0.128 to 0.091. This means we can postpone transmission expansion by
making wheeling transactions in proper direction. In some cases it may be beneficial to buy
expensive power from some control areas and sell it to other control areas in cheaper price to
release transmission capacity and postpone transmission expansion. In general a wheeling
transaction may congest some lines and release the capacity of some other transmission lines.
LMP of bus No. 2 in $/MWhr
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30
25
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15
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5