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3 Existing Analytic Methods and Tools
Pages 44-60

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From page 44...
... In order to estimate the mathematical and computational research needed for the next-generation electric grid it will be important to first consider some of the existing analytic methods that are used in this already quite sophisticated software to plan and operate the grid of today. Building on the foundation described in Chapters 1 and 2, such consideration is the purpose of this chapter.
From page 45...
... , generator and load parameters (including their net power injection values) , and transmission line and transformer parameters.
From page 46...
... the power flow could be used to determine the consequences of proposed system changes, such as new transmission and generation, coupled with changes in the load. Historically there has been a difference between how the power system is represented in real-time power flows and the longer-term planning power flows.
From page 47...
... For example, opening a transmission line would cause a change in the bus voltage magnitudes. A number of continuous and discrete control devices would respond to changes in the bus voltages, including generator reactive power outputs, static var compensators, transformer LTC taps, and automatically switched shunts.
From page 48...
... Complicating convergence is the presence of many additional system automatic controls that must be considered, including discrete controls with either narrow regulation ranges that might not allow for a solution, or wide ranges that allow for a range of solutions. The use of proprietary or specific control algorithms for particular apparatus, as opposed to generic models, creates issues when exchanging cases between different software packages.
From page 49...
... The OPF has been a topic of research and development since the 1950s, when the first digital power flow algorithms were introduced for economic dispatch of the power grid. The problem becomes one of finding the best set of control variables (generation, voltage set points, and so on)
From page 50...
... The output is the estimated state variables (e.g., the voltage magnitudes and angles) , which can then be used to determine the real-time power flow solution that best matches the system measurements.
From page 51...
... at about 30 times per second, has allowed the development of "direct" state estimation, meaning that explicit, direct noniterative solutions of the power flow equations using phase angles (as measured) as inputs are possible; this is also known as a linear SE.
From page 52...
... Within North America, TS cases are available for all four major interconnects.4 Large-scale studies done for the Western Interconnection and the Electric Reliability Corporation of Texas interconnection usually include a representation of the entire interconnect, whereas for the large Eastern Interconnection (which includes the Quebec Interconnection) an equivalenced representation is often used.
From page 53...
... This is an area in which new data-driven models based on machine learning could play a significant role. As was the case with the power flow, one difficulty potentially impeding research is that some of the transient stability models used in systemwide studies are not publicly available.
From page 54...
... . Recommendation 3: The Federal Energy Regulatory Commission should require that descriptions of all models used in systemwide transient stability studies be fully public, including descriptions of any associated text file formats.
From page 55...
... ELECTROMAGNETIC TRANSIENTS The transmission lines can be represented as a form of waveguide or transmission pipe for the purpose of assessing wave propagation down the line. At every change of impedance along the line in a network, reflections are created.
From page 56...
... While interconnection standards tightly limit the harmonic content that individual inverters may introduce into the system, the presence of multiple inverter-based resources in close proximity (as with a new transmission line to a region having many wind farms) can cause interference effects among the multiple harmonic sources.
From page 57...
... the SCUC can produce nodal prices. Applications of MIP for unit scheduling include market operations; generator operator simulation of markets for bidding support; annual production costing for studying future generation portfolios; renewable penetrations; impacts of transmission planning; and generation interconnection studies, including the probability of wind curtailment for transmission constraints.
From page 58...
... . For example, GICs can be calculated for assumed uniform or nonuniform electric field variations and simultaneously their transformer impact integrated into the power flow calculations.
From page 59...
... IEEE Transactions on Power Apparatus and Systems PAS-88(4)
From page 60...
... IEEE Transactions on Power Apparatus and Systems PAS-102(12)


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