# Co-optimization of electricity transmission and generation resources for planning and policy analysis: review of concepts and modeling approaches

## Abstract

The recognition of transmission’s interaction with other resources has motivated the development of co-optimization methods to optimize transmission investment while simultaneously considering tradeoffs with investments in electricity supply, demand, and storage resources. For a given set of constraints, co-optimized planning models provide solutions that have lower costs than solutions obtained from decoupled optimization (transmission-only, generation-only, or iterations between them). This paper describes co-optimization and provides an overview of approaches to co-optimizing transmission options, supply-side resources, demand-side resources, and natural gas pipelines. In particular, the paper provides an up-to-date assessment of the present and potential capabilities of existing co-optimization tools, and it discusses needs and challenges for developing advanced co-optimization models.

## Keywords

Co-optimization Transmission expansion planning Generation expansion planning Model fidelity Energy storage Demand response Integrated network uncertainty Long-term planning AC and DC power flow## Notes

### Acknowledgments

The authors would like to acknowledge the National Association of Regulatory Utility Commissioners (NARUC) for supporting our efforts in writing the whitepaper on co-optimization [23]. The authors are also grateful to Bob Pauley, Doug Gotham, Stan Hadley, and Patrick Sullivan for their comments. Opinions expressed in this paper, however, as well as any errors or omissions, are the authors’ alone.

## References

- 1.Sauma, E.E., Oren, S.S.: Proactive planning and valuation of transmission investments in restructured electricity markets. J. Regul. Econ.
**30**(3), 261–290 (2006). (358–387)CrossRefGoogle Scholar - 2.Krishnan, V., McCalley, J., Lemos, S., Bushnell, J.: Nation-wide transmission overlay design and benefits assessment for the US. Energy Policy (2013). doi: 10.1016/j.enpol.2012.12.051
- 3.McCalley, J., Krishnan, V., Gkritza, K., Brown, R., Mejia-Giraldo, D.: Planning for long haul- Investment strategies for national energy and transportation infrastructures. IEEE Power Energy Mag.
**11**(5), 24–35 (2013)CrossRefGoogle Scholar - 4.Shahidehpour, M.: Investing in expansion: the many issues that cloud electricity planning. IEEE Power Energy Mag.
**2**, 14–18 (2004)CrossRefGoogle Scholar - 5.Awad, M., Casey, K.E., Geevarghese, A.S., Miller, J.C., Rahimi, A.F., Sheffrin, A.Y., Zhang, M., Toolson, E., Drayton, G., Hobbs, B.F., Wolak, F.A.: Economic assessment of transmission upgrades: application of the California ISO approach, Ch. 7. In: Zhang, X. (ed.) Restructured Electric Power Systems: Analysis of Electricity Markets with Equilibrium Models, Power Engineering Series, pp. 241–270. J. Wiley & Sons/IEEE Press, New York (2010)CrossRefGoogle Scholar
- 6.Gu, Y., McCalley, J.D., Ni, M.: Coordinating large-scale wind integration and transmission planning. IEEE Trans. Sustain. Energy
**3**(4), 652–659 (2012)CrossRefGoogle Scholar - 7.McCalley, J., Bushnell, J., Krishnan, V., Cano, S.: Transmission design at the national level: benefits, risks and possible paths forward. In: White Paper to PSERC, The Future Grid to Enable Sustainable Energy Systems. http://www.pserc.wisc.edu/research/FutureGrid/broadanalysis.aspx (2012)
- 8.Roh, J.H., Shahidehpour, M., Fu, Y.: Market-based coordination of transmission and generation capacity planning. IEEE Trans. Power Syst.
**22**(4), 1406–1419 (2007)CrossRefGoogle Scholar - 9.Short, W., et al.: Regional energy deployment system (ReEDS). NREL Technical Report NREL/TP-6A20-46534. http://www.nrel.gov/analysis/reeds/pdfs/reeds_documentation.pdf (2011)
- 10.van der Weijde, A.H., Hobbs, B.F.: The economics of planning electricity transmission to accommodate renewables: using two-stage optimisation to evaluate flexibility and the cost of disregarding uncertainty. Energy Econ.
**34**(5), 2089–2101 (2012)CrossRefGoogle Scholar - 11.Zheng, Q.P., Liu, A.L.: Transmission and generation capacity expansion with unit commitment: a multiscale stochastic model. Presentation at the INFORMS Annual Meeting (2011)Google Scholar
- 12.Pfeifenberger, J.P., Hou, D.: Transmission’s true value: adding up the benefits of infrastructure investments. Publ. Util. Fortnightly, 44–50. http://www.fortnightly.com/fortnightly/2012/02/ (2012)
- 13.Chang, J.W., Pfeifenberger, J.P., Hagerty, J.M.: A WIRES report on the benefits of electric transmission: identifying and analyzing the value of investments. http://www.WIRESgroup.com The Brattle Group (2013)
- 14.Sauma, E., Oren, S.: Economic criteria for planning transmission investment in restructured electricity markets. IEEE Trans. Power Syst.
**22**(4), 1394–1405 (2007)CrossRefGoogle Scholar - 15.Pozo, D., Contreras, J., Sauma, E.: If you build it, he will come: anticipative power transmission planning. Energy Econ.
**36**, 135–146 (2013)CrossRefGoogle Scholar - 16.Hobbs, B.F.: Regional energy facility location models for power system planning and policy analysis. In: Lev, B., Murphy, F., Bloom, J., Gleit, A. (eds.) Analytic Techniques for Energy Planning, pp. 53–66. North-Holland Press, Amsterdam (1984)Google Scholar
- 17.Stoll, H.: Least-Cost Electric Utility Planning. John Wiley, New York (1989)Google Scholar
- 18.International Atomic Energy Agency: Expansion Planning for Electrical Generating Systems: A Guidebook (1984)Google Scholar
- 19.Wang, X., McDonald, J.: Modern Power System Planning. McGraw Hill Book Company, London (1994)Google Scholar
- 20.Ventosa, M., Baíllo, Á., Ramos, A., Rivier, M.: Electricity markets modeling trends. Energy Policy
**33**(7), 897–913 (2005)CrossRefGoogle Scholar - 21.Madrigal, M., Stoft, S.: Transmission Expansion for Renewable Energy Scale-Up: Emerging Lessons and Recommendations. World Bank, Washington, DC (2012)CrossRefGoogle Scholar
- 22.Areiza, J.M., Latorre, G., Cruz, R.D., Villegas, A.: Classification of publications and models on transmission expansion planning. IEEE Trans. Power Syst.
**18**(02), 938–946 (2003)CrossRefGoogle Scholar - 23.Liu, A., Zheng, Q., Ho, J., Krishnan, V., Hobbs, B., Shahidehpour, M., McCalley, J.: Co-optimization of Transmission and Other Supply Resources, NARUC Project No. 3316T5, prepared for the Eastern Interconnection States Planning Council. Available at: http://www.naruc.org/grants/Documents/Co-optimization-White-paper_Final_rv1.pdf (2013). Accessed 1 Sep 2013
- 24.Khodaei, A., Shahidehpour, M.: Microgrid-based co-optimization of generation and transmission planning in power systems. IEEE Trans. Power Syst.
**28**(2), 1582–1590 (2013)CrossRefGoogle Scholar - 25.Turvey, R., Anderson, D.: Electricity Economics: Essays and Case Studies. Johns Hopkins University Press, Baltimore (1977)Google Scholar
- 26.Hobbs, B.F., Hu, M., Chen, Y., Ellis, J.H., Paul, A., Burtraw, D., Palmer, K.L.: From regions to stacks: spatial and temporal downscaling of future pollution scenarios for the power sector. IEEE Trans. Power Syst.
**25**(2), 1179–1189 (2010)CrossRefGoogle Scholar - 27.ICF Inc, Integrated Planning Model. http://www.icfi.com/insights/products-and-tools/ipm Fairfax (2013)
- 28.Sawey, R., Zinn, C.: A mathematical model for long range expansion of generation and transmission in electric utility systems. IEEE Trans. Power Apparatus Syst.
**96**(2), 657–666 (1977)CrossRefGoogle Scholar - 29.Pereira, M., Pinto, L., Cunha, S., Oliveira, G.: A decomposition approach to automated generation/transmission expansion planning. IEEE Trans. Power Apparatus Syst.
**104**(11), 3074–3083 (1985)CrossRefGoogle Scholar - 30.Li, W., Billinton, R.: A minimum cost assessment method for composite generation and transmission system expansion planning. IEEE Trans. Power Syst.
**8**(2), 628–635 (1993)Google Scholar - 31.Alizadeh, B., Jadid, S.: Reliability constrained coordination of generation and transmission expansion planning in power systems using mixed integer programming. IET Gener. Transm. Distrib.
**5**(9), 948–960 (2011)CrossRefGoogle Scholar - 32.Motamedi, A., Zareipour, H., Buygi, M.O., Rosehart, W.D.: A transmission planning framework considering future generation expansions in electricity markets. IEEE Trans. Power Syst.
**25**(4), 1987–1995 (2010)CrossRefGoogle Scholar - 33.Murugan, P., Kannan, S., Baskar, S.: Application of NSGA-II algorithm to single objective transmission constrained generation expansion planning. IEEE Trans. Power Syst.
**24**(4), 1790–1797 (2009)CrossRefGoogle Scholar - 34.Sepasian, M., Seifi, H., Foroud, A., Hatami, A.: A multiyear security constrained hybrid generation-transmission expansion planning algorithm including fuel supply costs. IEEE Trans. Power Syst.
**24**(3), 1609–1618 (2009)CrossRefGoogle Scholar - 35.Baringo, L., Conejo, A.J.: Transmission and Wind Power Investment. IEEE Trans. Power Syst.
**27**(2), 885–893 (2012)CrossRefGoogle Scholar - 36.Tor, O., Guven, A., Shahidehpour, M.: Congestion-driven transmission planning considering the impact of generator expansion. IEEE Trans. Power Syst.
**23**(2), 781–790 (2008)CrossRefGoogle Scholar - 37.Tor, O., Guven, A., Shahidehpour, M.: Promoting the investment on IPPs for optimal grid planning. IEEE Trans. Power Syst.
**25**(3), 1743–1750 (2010)CrossRefGoogle Scholar - 38.Head, W.J., Nguyen, H.V., Kahle, R.L., Bachman, P.A., Jensen, A.A., Watry, S.J.: The procedure used to assess the long range generation and transmission resources in the Mid-Continent Area Power Pool. IEEE Trans. Power Syst.
**5**(4), 1137–1145 (1990)CrossRefGoogle Scholar - 39.Castillo, A., O’Neill, R.P.: Computational performance of solution techniques applied to the ACOPF, Optimal power flow paper-5, FERC staff paper (2013)Google Scholar
- 40.Model Types, General Algebraic Modeling System (GAMS). http://www.gams.com/modtype/index.htm (2014). Accessed 07 March 2014
- 41.Zhang, H., Heydt, G.T., Vittal, V., Mittelman, H.D.: Transmission Expansion Planning Using an AC Model: Formulations and Possible Relaxations IEEE PES General Meeting (2012)Google Scholar
- 42.Jabr, R.: Optimization of AC transmission system planning. IEEE Trans. Power Syst.
**28**(3), 2779–2787 (2013)CrossRefGoogle Scholar - 43.Taylor, J., Hover, F.: Conic AC transmission system planning. IEEE Trans. Power Syst.
**28**(2), 952–959 (2013)CrossRefGoogle Scholar - 44.Bent, R., Coffrin, C., Gumucio, R., van Hentenryck, P.: Transmission Network Expansion Planning: Bridging the Gap between AC Heuristics and DC Approximations. PSCC (2014)Google Scholar
- 45.Krishnan, V., Liu, H., McCalley, J.D.: Coordinated reactive power planning against power system voltage instability. In: Proceedings of IEEE/PES Power Systems Conference and Expo. (2009)Google Scholar
- 46.Li, Y., McCalley, J.: Design of a high capacity inter-regional transmission overlay for the U.S. IEEE Trans. Power Syst.
**30**(1), 513–521 (2015)CrossRefGoogle Scholar - 47.Gutman, R., Marchenko, P.P., Dunlop, R.D.: Analytical development of loadability characteristics for EHV and UHV transmission lines. IEEE Trans. Power Apparatus Syst.
**PAS–98**(2), 606–617 (1979)CrossRefGoogle Scholar - 48.Quelhas, A.M., Gil, E., McCalley, J.D.: A multiperiod generalized network flow model of the U.S. integrated energy system: Part I-model description. IEEE Trans. Power Syst.
**22**, 829–836 (2007)CrossRefGoogle Scholar - 49.Bertsekas, D.P., Polymenakos, L.C., Tseng, P.: Epsilon-relaxation method for separable convex cost network flow problems. SIAM J. Optim.
**7**, 853–870 (1997)MathSciNetCrossRefzbMATHGoogle Scholar - 50.Ding, J., Somani, A.: Parallel computing solution for capacity expansion network flow optimization problems. J. Comput.
**4**(7), (2012)Google Scholar - 51.McCalley, J., Krishnan, V.: Survey of transmission technologies for planning long distance bulk transmission overlay in US. Int. J. Electr. Power Energy Syst.
**54**, 559–568 (2014)CrossRefGoogle Scholar - 52.Mohitpour, M., Golshan, H., Murray, A.: Pipeline Design and Construction: A Practical Approach, 3rd edn. American Society of Mechanical Engineers (2007)Google Scholar
- 53.Lamont, A.: User’s guide to the META-Net economic modeling system; version 1.2, Lawrence Livermore National Laboratory, UCRL-ID-122511 (1994)Google Scholar
- 54.Gabriel, S.A., Conejo, A.J., Fuller, J.D., Hobbs, B.F., Ruiz, C.: Complementarity Modeling in Energy Markets. Springer-Verlag, Berlin (2012)zbMATHGoogle Scholar
- 55.Lund, H., Kempton, W.: Integration of renewable energy into the transport and electricity sectors through V2G. Energy Policy
**36**(9), 3578–3587 (2008)CrossRefGoogle Scholar - 56.Krishnan, V., Gonzalez-Marciaga, L., McCalley, J.: A planning model to assess hydrogen as an alternative fuel for national light-duty vehicle portfolio. Energy
**73**(14), 943–957 (2014)CrossRefGoogle Scholar - 57.Connolly, D., Lund, H., Mathiesen, B.V., Leahy, M.: A review of computer tools for analysing the integration of renewable energy into various energy systems. Appl. Energy
**87**(4), 1059–1082 (2010)CrossRefGoogle Scholar - 58.Lund, H., Werner, S., Wiltshire, R., Svendsen, S., Thorsen, J.E., Hvelplund, F., Mathiesen, B.V.: 4th Generation District Heating (4GDH). Integrating smart thermal grids into future sustainable energy systems. Energy
**68**, 1–11 (2014)CrossRefGoogle Scholar - 59.Krishnan, V., Das, T., McCalley, J.D.: Impact of short-term storage on frequency response under increasing wind penetration. J. Power Sources (2014)Google Scholar
- 60.Krishnan, V., Das, T.: Optimal allocation of energy storage in a co-optimized electricity market: Benefits assessment and deriving indicators for economic storage ventures. Energy
**81**, 175–188 (2015)CrossRefGoogle Scholar - 61.Das, T.: Performance and economic evaluation of storage technologies. Ph.D. Dissertation, Iowa State University (2013)Google Scholar
- 62.Das, T., Krishnan, V., McCalley, J.D.: Incorporating cycling costs in generation dispatch program: an economic value stream for energy storage. Int. J. Energy Res.
**38**(12), 1551–1561 (2014)CrossRefGoogle Scholar - 63.Navid, N., Rosenwald, G.: Market solutions for managing ramp flexibility with high penetration of renewable resource. Sustain. Energy IEEE Trans.
**3**(4), 784–790 (2012)CrossRefGoogle Scholar - 64.Das, T., Krishnan, V., McCalley, J.: High-fidelity dispatch model of storage technologies for production costing studies. IEEE Trans. Sustain. Energy
**5**(4), 1242–1252 (2014)CrossRefGoogle Scholar - 65.Das, T., Krishnan, V., McCalley, J.D.: Assessing the benefits and economics of bulk energy storage technologies in the power grid. Appl. Energy
**139**, 104–118 (2015)CrossRefGoogle Scholar - 66.Krishnan, V., Das, T., Ibanez, E., Lopez, C.A., McCalley, J.D.: Modeling operational effects of wind generation within national long-term infrastructure planning software. IEEE Trans. Power Syst.
**28**(2), 1308–1317 (2013)CrossRefGoogle Scholar - 67.Walawalkar, R., Apt, J., Mancini, R.: Economics of electric energy storage for energy arbitrage and regulation in New York. Energy Policy
**35**(4), 2558–2568 (2007)CrossRefGoogle Scholar - 68.Hedman, K.W., Oren, S.S., O’Neill, R.P.: A review of transmission switching and network topology optimization. In: IEEE Power and Energy Society General Meeting (2011)Google Scholar
- 69.Grinold, R.C.: Model building techniques for the correction of end effects in multistage convex programs. Oper. Res.
**31**(3), 407–431 (1983)CrossRefzbMATHGoogle Scholar - 70.Krishnan, V., McCalley, J.D.: Building foresight in long-term infrastructure planning using end-effect mitigation models. IEEE Syst. J.
**PP**(99), 1–12 (2015)Google Scholar - 71.MISO Transmission Expansion Plan 2012: Appendix E2 EGEAS, Assumptions DocumentGoogle Scholar
- 72.De Jonghe, C., Hobbs, B.F., Belmans, R.: Optimal generation mix with short-term demand response and wind penetration. IEEE Trans. Power Syst.
**27**(2), 830–839 (2012)CrossRefGoogle Scholar - 73.López, J.A., Ponnambalam, K., Quintana, V.H.: Generation and transmission expansion under risk using stochastic programming. IEEE Trans. Power Syst.
**22**(3), 1369–1378 (2007)CrossRefGoogle Scholar - 74.Roh, J.H., Shahidehpour, M., Wu, L.: Market-based generation and transmission planning with uncertainties. IEEE Trans. Power Syst.
**24**(3), 1587–1598 (2009)CrossRefGoogle Scholar - 75.Mejia-Giraldo, D.: Robust and flexible planning of power system generation capacity. Graduate Theses and Dissertations. Paper 13225. http://lib.dr.iastate.edu/etd/13225 (2013)
- 76.Pozo, D., Sauma, E., Contreras, J.: A three-level static MILP model for generation and transmission expansion planning. IEEE Trans. Power Syst.
**28**(1), 202–210 (2013)CrossRefGoogle Scholar - 77.Denholm, P., Drury, E., Margolis, R.: The solar deployment system (SolarDS) model: documentation and sample results. Technical Report, NREL/TP-6A2-45832, Sep 2009Google Scholar
- 78.Krishnan, V., Kastrouni, E., Pyrialakou, D., Gkritza, K., McCalley, J.: An optimization model of energy and transportation systems: assessing the high-speed rail impact in the United States. Transp. Res. Part C: Emerg. Technol.
**54**, 131–156 (2015)CrossRefGoogle Scholar