Integrating Southwest Power Pool Wind to Southeast Electricity ...

participants the possibility of a related, but separately funded project to develop a
reasonable transmission network for 2022 that would provide for high wind transfers.
Funding and man-power resources for the partner study were not available.
2. Unconstrain the transmission in the 2022 Non-RES model by removing the thermal rating
limits and associated losses. While a complete “copper sheet” type analysis is quite
simplistic and unrealistic, it does approximate a scenario where sufficient transmission
would be built to deliver wind energy from SPP to SERC if 48 GW of wind capacity
were developed in SPP. This approach has some obvious implications for the results of
the SCUC/SCED simulations that must be considered when interpreting the results.
Additional analysis was performed to better understand the implications of the
“unconstrained” assumption.
As described in detail in the Task 1 Report, UPLAN is the SCUC/SCED simulation platform
used for this study. UPLAN has three different internal algorithms for integrating power flow
within its Unit Commitment and Economic Dispatch: AC-OPF; DC-OPF; and Transportation. In
AC, a non-linear problem is developed to describe the energy flow through each element of the
system which considers Kirchoff’s laws, voltage and losses directly within the formulation. DC
is a linear approximation of the AC power flow which, in the case of UPLAN, can consider
losses but not voltage. The transportation method does not model the losses, the voltage, or
Kirchoff’s laws. It does, however, consider all the physical connections as though they were
pipelines. Power can flow anywhere without exceeding specified line capacity, in much the
same that way water or gas pipelines are constrained. The transportation model also does
consider hurdle rates or wheeling charges.
For the “Constrained” 7 GW and 14 GW scenarios discussed in the Task 1 Report and thus far in
this report, the DC model was utilized. As noted above, in order to ascertain the impact of
utilizing the UPLAN Transportation mode for the High Wind Transfer cases, a quantitative
analysis was conducted for the following 14 GW scenarios to isolate the impact of removing
losses and removing thermal constraints:
1. 14 GW constrained w/losses (14 GW) – 14 GW scenario solved with DC OPF
representing both losses and thermal constraints (scenario already described and
summarized in previous section).
2. 14 GW constrained no losses (14 GW-NL) – 14 GW scenario solved with DC OPF
respecting thermal constraints as in #1, but with the losses not calculated.
3. 14 GW unconstrained no losses (14 GW-UC) – 14 GW scenario solved in Transportation
mode ignoring both thermal constraints and losses.
Figure 2-1 shows a comparison of the aggregate average net flow out of each of the SPP and
large eastern SERC regions for these three 14 GW cases. Comparison of the 14 GW (red) and
14 GW-NL (purple) data in the bar chart shows that removing losses alone has a small impact on
the generation flows between regions suggesting that losses do not play a primary role in
restricting economic transfers across the region. Comparison of the 14 GW-NL (purple) and 14
GW-UC (green) data in the bar chart, however, shows that removing thermal constraints
significantly changes the flows between regions. This is expected given that removing
transmission constraints allows generation to flow between areas based on the relative economics
2-3