Future-frequency stability | Grid Optimization Competition

From Manuel Garcia e-mail of 4/11/2024 at 7:04PM

A few references on the topic of frequency stability constraints for economic dispatch and unit commitment problems and a brief description of the literature.

There are typically regulations that require ISOs to accommodate some “largest contingency,” e.g. the simultaneous outage of two nuclear generators. As a result, much of the literature focuses on ensuring frequency stability following the specified “largest contingency.” Most of the work on this topic enforces stability constraints through reserve requirements that ensure stability; however, there are some works that do not explicitly mention reserve and instead characterize stability with respect to the generation dispatch.

Different stability metrics have been used when defining stability constraints. Here are the three most common:

Frequency nadir limits: Ensure that the frequency does not drop below some threshold at which firm load begins to shed.
Rate-of-change-of-Frequency (ROCOF) limits: Ensure the ROCOF does not exceed some threshold at which relays are triggered.
Rotor angle difference limits: ensure the maximum difference between any two generator angles is limited to maintain synchronization.

The “frequency nadir limits” and “ROCOF limits” intend to avoid relays from tripping, which could trigger cascading outages. In contrast, rotor angle difference limits serve as a proxy. for generators losing synchronization and the exact limit that should be used is not immediately clear.

Each of these stability metrics are generally difficult to characterize mathematically, are non-linear functions of the UC/ED decision variables and depend on the detailed dynamic model of the power system. As a result, these stability constraints cannot be directly implemented into a UC/ED problem in a computationally efficient way and are instead approximated using various methods.

Previous work uses either a “first principles approach” or an “empirical approach” to deriving stability constraints. First principles approaches require assumptions and approximations to facilitate theoretical derivations. Empirical approaches use dynamic simulation to empirically construct stability constraints. ERCOT uses an empirical approach to construct their frequency nadir requirement; however, their approach isn’t perfect as explained in my paper. Some very recent work has started incorporating neural network surrogate models into UC/ED problems.

References

Zhou, Jianguo, Ye Guo, Lun Yang, Jiantao Shi, Yi Zhang, Yushuai Li, Qinglai Guo,Hongbin Sun. “A review on frequency management for low-inertia power systems: From inertia and fast frequency response perspectives,” Electric Power Systems Research, Volume 228, 110095, 2024. https://doi.org/10.1016/j.epsr.2023.110095. This is a recent paper that provides a review of both ISO current practices and optimization methods from the literature. Section 2.2.1 covers stability constraints for unit commitment and economic dispatch problems.

First Principles

Badesa, Luis, Fei Teng and Ggoran Strbac, "Conditions for Regional Frequency Stability in Power System Scheduling—Part I: Theory," in IEEE Transactions on Power Systems, vol. 36, no. 6, pp. 5558-5566, Nov. 2021. https://doi.org/10.1109/TPWRS.2021.3073083.

Badesa, Luis, Fei Teng and Ggoran Strbac, "Conditions for Regional Frequency Stability in Power System Scheduling—Part II: Application to Unit Commitment," in IEEE Transactions on Power Systems, vol. 36, no. 6, pp. 5567-5577, Nov. 2021. https://doi.org/10.1109/TPWRS.2021.3073077.

Chávez, Héctor, Ross Baldick and Sandip Sharma, "Governor Rate-Constrained OPF for Primary Frequency Control Adequacy," in IEEE Transactions on Power Systems, vol. 29, no. 3, pp. 1473-1480, May 2014, https://doi.org/10.1109/TPWRS.2014.2298838.

ERCOT

Du, Pengwei, weifeng Li, Qinran Hu, Tao Ding, “New Ancillary Service Market for ERCOT,” in IEEE Access, vol. 8, pp. 178391-178401, 2020. https://doi.org/10.1109/ACCESS.2020.3027722

Liu, Cong, and Pengwei Du, "Participation of Load Resources in Day-Ahead Market to Provide Primary-Frequency Response Reserve," in IEEE Transactions on Power Systems, vol. 33, no. 5, pp. 5041-5051, Sept. 2018. https://doi.org/10.1109/TPWRS.2018.2818948.

Li, Weifeng, Pengwei Du and Ning Lu, "Design of a New Primary Frequency Control Market for Hosting Frequency Response Reserve Offers From Both Generators and Loads," in IEEE Transactions on Smart Grid, vol. 9, no. 5, pp. 4883-4892, Sept. 2018. https://doi.org/10.1109/TSG.2017.2674518.

Garcia

Garcia, Manuel, and Ross Baldick, “Real-Time Co-Optimization: Interdependent Reserve Types for Primary Frequency Response,” in e-Energy '19: Proceedings of the Tenth ACM International Conference on Future Energy Systems, June 2019, Pages 550–555. https://doi.org/10.1145/3307772.3335319

Garcia, Manuel, and Ross Baldick, "Requirements for Interdependent Reserve Types Providing Primary Frequency Control," in IEEE Transactions on Power Systems, vol. 37, no. 1, pp. 51-64, Jan. 2022. https://doi.org/10.1109/TPWRS.2021.3094214.

Garcia, Manuel, and Ross Baldick, Felipe Wilches-Bernal, “Primary Frequency Response Reserve Products for Inverter-Based Resources,” in Proceedings of the 55th Hawaii International Conference on System Sciences, 2022. https://scholarspace.manoa.hawaii.edu/bitstreams/2ea8ec65-41f1-4213-bc08-e3d3dd473eec/download.

Garcia, Manuel, J. Kyle Skolfield, Felipe Wilches-Bernal, Ross Baldick. “Co-Optimization of Ancillary Services Providing Primary Frequency Control in the Day-Ahead Market,” in IEEE PES Transactions on Power Systems, submitted 2024. download but do not distribute

Neural Network Surrogates

Wu, Tao and Jianhui Wang, "Transient Stability-Constrained Unit Commitment Using Input Convex Neural Network," in IEEE Transactions on Neural Networks and Learning Systems. https://doi.org/10.1109/TNNLS.2023.3291673.

Y. Zhang et al., "Encoding Frequency Constraints in Preventive Unit Commitment Using Deep Learning With Region-of-Interest Active Sampling," in IEEE Transactions on Power Systems, vol. 37, no. 3, pp. 1942-1955, May 2022. https://doi.org/10.1109/TPWRS.2021.3110881.