Policy, Markets, and Computation

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    Evaluating Benefits of Rolling Horizon Model Predictive Control for Intraday Scheduling of a Natural Gas Pipeline Market
    ( 2019-01-08) Rudkevich, Aleksandr ; Zlotnik, Anatoly ; Li, Xindi ; Ruiz, Pablo ; Beylin, Aleksandr ; Goldis, John ; Tabors, Richard ; Philbrick, Russ
    This paper analyzes a mechanism for clearing a physical market for intra-day schedules of receipts and deliveries of a natural gas pipeline. The Gas Balancing Market (GBM) is implemented to trade deviations from previously confirmed ratable nominations by solving a rolling horizon model predictive control (MPC) optimization formulation. The GBM mechanism operates by accepting quantity/price offers and bids from sellers and buyers of gas and producing an economically optimal schedule while guaranteeing its physical feasibility. The GBM’s solution engine is based on a strict mathematical representation of engineering factors of transient pipeline hydraulics and compressor station operations. The GBM’s settlement of cleared transactions is based on Locational Trade Values (LTVs) of natural gas that are fully consistent with the physics of energy flow. In this paper we provide numerical results of simulating a hypothetical GBM market operation using historical SCADA data for an actual pipeline system operation during the Polar Vortex period of February – March 2014. Based on these simulations, we quantify the potential deliverability and economic benefits of the GBM utilizing transient optimization of pipeline operations.
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    The Hidden Cost of Priority Dispatch for Wind Power
    ( 2019-01-08) Patsakis, Georgios ; Oren, Shmuel
    Renewable generation, such as wind power, is commonly considered a must-take resource in power systems. In this work we show that, given the technical capabilities of current wind turbines, this approach could lead to major economic inefficiency as wind integration levels in power systems increase. We initially provide intuition for cases in which the optimal operating point involves shedding renewable generation, even though no cost is associated with it in the optimization objective, illustrated in small power systems. We then explore the expected benefit from dispatching wind resources at a lower level than their available output in a Stochastic Unit Commitment (SUC) framework. The modeling and evaluation approach adopted are described. A decomposition technique based on recent literature that utilizes global cuts and Lagrangian penalties to achieve convergence is used to solve the resulting large scale mixed integer optimization problem, in a high performance computing environment. A reduced California system is examined as a test case.
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    Monotonicity Between Phase Angles and Power Flow and Its Implications for the Uniqueness of Solutions
    ( 2019-01-08) Park, SangWoo ; Zhang, Richard ; Lavaei, Javad ; Baldick, Ross
    This paper establishes sufficient conditions for the uniqueness of power flow solutions in an AC power system via the monotonic relationship between real power flow and the phase angle difference. More specifically, we prove that strict monotonicity holds if the angle difference is bounded by the steady-state stability limit in a power system with a series-parallel topology, or if transmission losses are sufficiently low. In both cases, a vector of voltage phase angles can be uniquely determined (up to an absolute phase shift) given a vector of active power injections within the realizable range. The implication of this result for classical power flow analysis is that, under the conditions specified above, the problem has a unique physically realizable solution if the phasor voltage magnitudes are tightly controlled.
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    Continuous-time Look-Ahead Scheduling of Energy Storage in Regulation Markets
    ( 2019-01-08) Khatami, Roohallah ; Parvania, Masood ; Khargonekar, Pramod
    Energy storage (ES) devices offer valuable flexibility services, including regulation reserve, in power systems operation that could improve the reliability and cost-efficiency of systems with high penetration of renewable energy resources. In this paper, a continuous-time look-ahead regulation capacity scheduling model is proposed, which more accurately models and schedules the regulation capacity trajectories provided by generating units and ES devices in real-time power systems operation. A function space solution method is proposed to reduce the dimensionality of the continuous-time problem by modeling the parameter and decision trajectories in a function space formed by Bernstein polynomials, which converts the continuous-time problem into a linear programming problem. Numerical results, conducted on the IEEE Reliability Test System, show lower operation cost and less regulation scarcity events in real-time power systems operation due to efficient deployment of the ES flexibility in regulation markets.
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    Should Natural Gas Be Shipped or Stored to Supply Power Plants?
    ( 2019-01-08) Blumsack, Seth
    Following a series of winters featuring extreme cold episodes in the Northeastern U.S., power grid operators have engaged in exercises focused on assessing fuel deliverability to power plants, particularly natural gas. These studies have raised important issues and identified possible scenarios that could contribute to reliability problems during winter peaks, but have not evaluated the economics of specific solutions to winter-time fuel deliverability. This paper describes an expansion to a new modeling framework for gas and electric power transmission planning problems (the Combined Electricity and Gas Expansion, or CEGE model) that allows centralized or distributed natural gas storage to be evaluated alongside traditional planning alternatives such as transmission network expansion. Using a test system based on the gas and electric transmission topology in New England, we develop a a simple two-period gas storage model and use this model to evaluate economically valuable locations for distributed natural gas storage and compare the economic merits of increasing storage within New England versus expanding pipeline infrastructure to increase fuel deliverability to New England power plants within our test system. Initial simulations using this storage model suggest that the optimal placement for gas storage may be co-located with power plants to relieve binding pressure constraints in areas of the gas network close to gas-fired generation. Moreover, the economic consequences of extreme winter peak scenarios may be ameliorated at a lower cost with a mix of gas storage and pipeline expansions rather than via pipeline expansion alone.