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7 Case Studies
Pages 111-127

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From page 111... ... PJM Market Operations coordinates the continuous buying, selling, and delivery of wholesale electricity through the energy market. In its role as market operator, PJM balances the needs of suppliers, wholesale customers, and other market participants, and monitors market activities to ensure open, fair, and equitable access. Read the entire page →
From page 112... ... NLi,t = no-load cost of unit i at time t Si,t = start-up cost of unit i at time t RCi,t = reserve cost of unit i at time t ASMWi,t = ancillary service (MW) of unit i at time t Cj,t = offer price of increment offer j at time t Ck,t = bid price of decrement bid k at time t INCj,t = MW for increment offer j at time t DECk,t = MW for decrement bid k at time t Cl,t = offer price or up-to-congestion transaction l at time t UTCl,t = MW of up-to-congestion transaction bid l at period t Cm,t = cost of economic load response resource m at time t ELRPm,t = MW of economic load response resource m at time t Um,t = commitment status of economic load response resource m at time t (0 or 1) Read the entire page →
From page 113... ... . , M min max where R t = reserve requirement at time t Pi,t max = maximum output limit of unit i at time t Pi,t min = minimum output limit of unit i and time t INCj,t min = maximum MW of increment offer j at time t DECk,t = max maximum MW of decrement offer k at time t UTCl,t = max maximum MW or up-to-congestion offer l at time t ELRPm,t = max maximum output limit of economic load response m at time t ELRPm,t = min minimum output limit of economic load response m at time t For simplicity, neither the objective function nor the constraints are shown in the above unit commitment problem formulation, but they are included in the actual day-ahead market clearing software. Read the entire page →
From page 114... ... uses the current operating state of the system provided by the state estimator as a set of initial conditions. The application then uses load and constraint forecast information for 7:55 a.m., in addition to generator offer information such as ramp rates and the real power minimum/maximum limits, to dispatch the set of online generation resources of PJM in a least-cost fashion to meet system expectations 10 min into the future. Read the entire page →
From page 115... ... If Moore's law continues to hold true, the increases in computer capability may be able to meet the needs of the current unit commitment problem PJM solves. This does not change the need for mathematical work in the short term, however, nor does it change the fact that the problem is likely to become substantially larger as the power grid changes. Read the entire page →
From page 116... ... In today's dc models, voltage and reactive constraints are linearized into dc approximations that attempt to model voltage restrictions that are real power flow limitations. This practice has been in place since the inception of power markets in the United States in the late 1990s; however, the practice still results in some unit commitment and market inefficiencies that a better model of ac constraints during the commitment, dispatch, and pricing process could improve. Read the entire page →
From page 117... ... . Yet, collectively, HILF events present an interesting case study on the mathematical and computational challenges needed for the next-generation electric grid. Read the entire page →
From page 118... ... GMDs start at the Sun, travel through space, interact with Earth's magnetic fields to induce electric fields at the surface that are dependent on the conductivity of Earth's crust going down hundreds of kilometers and that ultimately cause quasi-dc currents to flow in the high-voltage transmission grid, saturating the transformers, causing increased power system harmonics, heating in the transformers, and higher reactive power loss and resulting in a potential voltage collapse (NERC, 2012) Read the entire page →
From page 119... ... The oldest and largest underground power distribution network in the world is that of New York City. A power failure in New York can be a catastrophic event, where several blocks of the city lose power simultaneously. Read the entire page →
From page 120... ... , has been collecting data about the power network since the power grid started, at the time of Thomas Edison. Back then, these data were collected for accounting purposes, but now ConEdison records data from many different sources so the data can be harnessed for better power grid operations. Read the entire page →
From page 121... ... The field of natural language processing involves using sophisticated clustering techniques, classification techniques, and language models to put unstructured text into structured tables that can be used for business intelligence applications. ConEdison, for instance, has generated over 140,000 free text documents describing power grid events over the last decade within Manhattan. Read the entire page →
From page 122... ... What this means is that some generators were serving load using infrastructure that was electrically separated from the remainder of the interconnected power grid. Historically, this situation would have been difficult to manage in the control room, and it would likely have required de-energizing the loads, connecting the generators to the remainder of the grid, then reconnecting the load in the restoration sequence of events. Read the entire page →
From page 123... ... electrical infrastructure damage associated with the 2008 Hurricane Gustav in southern Louisiana. SOURCE: Entergy, "Images – Gustav Damage," image gallery, 7.4 http://www.entergy.com/2008_hurricanes/gustav_media.aspx. Read the entire page →
From page 124... ... Because the relative phase angles between different regions of the power grid are directly proportional to the real power flowing across the network, displaying the phase angles across a wide-area power system depicts the power flowing across the network in a comprehensive and intuitive manner. Also, because it is also affected by the net impedance between different points in the network, the phase angle can also serve as a proxy for system stress across critical boundaries. Read the entire page →
From page 125... ... However, the controls on the Texas equipment did not work properly, and this led to oscillatory dynamics between the controllers of wind power farms and line flow controllers of weak transmission lines delivering wind power to the faraway loads such as Dallas. The new technical term for these instabilities is subsynchronous control instabilities, which had not been experienced by any power grid before the situation in Texas. Read the entire page →
From page 126... ... Most models currently used in control centers do not even attempt to model the fast dynamics relevant for assessing the performance of power electronically switched auto mation embedded in different components throughout the complex power grids. This is a very difficult problem since it requires accurate modeling of fast nonlinear dynamics and control design, which are often close to bifurcation point conditions. Read the entire page →
From page 127... ... CASE STUDIES 127 Stockton, P Read the entire page →

From page 111...

... PJM Market Operations coordinates the continuous buying, selling, and delivery of wholesale electricity through the energy market. In its role as market operator, PJM balances the needs of suppliers, wholesale customers, and other market participants, and monitors market activities to ensure open, fair, and equitable access.

7 Case Studies Pages 111-127

7 Case Studies
Pages 111-127