PJM Base Case Setup Process
Motivation: PJM Network Model power flow cases typically have a large generation/load imbalance that result in large positive or negative generation at the island slack bus and distorted flows on nearby lines and transformers. The island slack bus is often located within PJM. A recent example has -6.6 GW at Peach Bottom (PEACHBOT 22.00 kV). Individual area AGC is generally not used (all areas are set to “Off AGC”). All generators outside of the PJM area are generally set to 0 MW output.
If we wish to perform analysis in area PJM, we need a good starting point. The island slack bus and the large generation/load imbalance that it carries will be moved to an external area, outside of PJM. Any major distortion of flows around the slack bus due to generation/load imbalance will then have less impact on the area we want to study.
An overview of a case development process follows:
- Solve the inner power flow with AGC and all voltage controls disabled in the Solution Options.
- Restore voltage controls, one option at a time, and solve power flow after each is restored. If restoring any option causes a power flow failure, it likely was not intended to be applied, and can be disabled again before proceeding.
- Set generation participation factors proportional to the size of the unit for all generators in the case.
- Set Unspecified MW exports = Actual Interchange for all areas to zero-out ACE before using AGC. Adjust AGC tolerance for each area to a small value (e.g. 5 MW) if needed.
- Set most areas to Participation Factor AGC except that which contains the island slack bus (usually PJM.)
- Restore AGC in the Solution Options and solve power flow.
- Move the island slack bus outside of PJM. A good choice might be the terminal bus of the largest generator outside PJM, defined by Min/Max MW. Set the area that now contains the island slack bus Off AGC.
- Set area PJM to Area Slack control, set the former island slack bus as the area slack, and solve the power flow.
- Optionally switch to the DC power flow approximation in Solution Options. (This may make the subsequent steps easier.) Set the DC loss multipliers by Area or Zone before closing the Solution Options dialog. Solve the power flow.
- Adjust exports from PJM to the island slack area so that the former island slack bus generator in PJM (e.g. Peach Bottom, or whatever was used) is restored to its min/max limit (whichever is closer to its starting point.) This may need to be done incrementally if the AC power flow is used.
These auxiliary files can perform the process, but some specifics may need to be adjusted to work with a particular PJM Network Model case. Many parameters reference specific bus numbers and area numbers. See the comments in each file for suggestions. The master file calls the other files. If an AC power flow solution is desired, skip the DC options auxiliary file. The power flow solution and other steps may need to be performed manually, outside of the auxiliary file, if the generation imbalance that is being moved outside of PJM is significant. (Shifting too much power in one step with an AC power flow solution may produce numerical instability.)
February 17, 2023