Electric Power Network

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Electric Power Network Tutorial: Basic Steady State & Dynamic Models for Control, Pricing and Optimization Christopher DeMarco Electrical and Computer Engineering & Power Systems Engineering Research Center www.pserc.org University of Wisconsin-Madison Madison, WI 53706 (608) 262-5546 demarco@engr.wisc.edu IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 2 Components of my talk: * Evangelism: for an audience likely focused on mathematical problems in communications networks, show what makes electric power networks different, and (hopefully) what makes them interesting. * Start with some "fun facts" - just general nature of technology involved, (opinionated) overview of nature of industry. * Move on to mathematical modeling - construct underlying dynamics, associated equilibrium for steady state. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 3 Highlight: - state equations associated with nodes; - role of network structure; - peculiar coordinate system used in dynamics and steady state; - policy/control decisions available; - market driven control & pricing. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 4 Old Assumptions under Regulated or State Monopoly * Ever increasing economies of scale for central generation plants - lowest production cost associated with central generating plants of increasing size. These economies of scale (historically) justified "natural monopoly" for generation. * Parallel independent transmission and distribution firms seen as highly inefficient. Long historic trend toward single interconnected synchronous grid covering large geographic area. Again, natural monopoly. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 5 What has Changed? i) Public perception of significant mis-steps in generation investment for many state/regulated monopoly firms (notable in US). Examples of billions of dollars of investment in partially constructed nuclear plants abandoned (interestingly, quite commensurate with billions of dollars of waste in CA markets ...) ii) Significant expansion of availability of natural gas, beyond estimates of one or two decades earlier. iii) Significant improvements in natural gas based prime movers; combined cycle gas turbines achieving efficiencies in high 50% range, from plants of medium size. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 6 iv) Strong political trends in many nations favoring market-based solutions over central planning solutions. Belief that private firms would make better investment decisions (editorial comment - evidence in US to date suggest private firms unable to make any investment decisions in transmission). IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 7 Common Features Emerging in Power Production in Many Parts of the World: * Assumption that distribution systems and (most of) transmission grid are still natural monopolies. Hence, these remain regulated, or state held. * Assumption that real time operation of transmission grid must lie in hands of centralized coordinating body, with considerable authority; oft-termed "Independent System Operator," or ISO. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 8 * Assumption that generation should be provided through competitive markets (though exact structure and rules for markets vary widely, and in many cases, are still evolving). * Many (not all) markets share a rough structure of day ahead offers made by independent generation companies, with a central market entity (ISO or Power Exchange) making initial plan of schedule/purchases. * Some markets allow independent arranged transactions between buyer & seller, "bilateral transaction." Coordinated with ISO, but not with central market. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 9 * Emerging efforts to bring larger number of power consumers to active participation into market, possibly down to retail level (terms: "retail competition," or "customer choice") IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 10 Generation Technology Overview * Key observation: conversion of mechanical energy to electrical energy via rotating machines is a highly refined technology - in excess of 98% efficient in modern machines. * But wide variations in efficiency lie in conversion process from chemical (or nuclear) energy to rotating mechanical power. * Large percentage of new generation around the world (and overwhelming majority in US) within last decade has natural gas as primary fuel; large percentage as gas turbines (irony - in 1970’s in US, natural gas was outlawed as a fuel for electric generation). IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 11 * Huge market demand for these units; before economic slowdown of 2001, growing concern regarding world-wide manufacturing capability - could it keep up with demand? * Increasing maximum size of units (e.g., 1000 MW - so apparent economies of scale showing up in this technology as well) IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 12 New Technologies in GT Units * Much advance due to improved materials, and improved computer tools for modeling and optimizing combustion and fluid flow designs. * Better materials allow higher firing temperatures, yields higher efficiency, while limiting NOx emissions. Potential efficiencies of 60% in combined cycle gas turbines. * Some manufacturers also examining steam cooling to raise efficiencies in simple cycle units (an example in partial operation: Lakeland Electric, Florida, USA site - 262 MW unit claiming 39% efficiency). IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 13 Aerospace Derivative Gas Turbines * "Aero" units often serve in smaller capacity (say ~5 to 50 MW) applications, where start/stop cycling for peaking may be necessary. * Simple cycle units, hence lower efficiency; however, some manufacturers claiming technology improvements bringing efficiency close to 40%. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 14 Heat Recovery Steam Generators (HRSG) Typical technology of older coal fired plants * Historic efficiencies in coal plants topped out around 35-39% * Advances in gas turbine technology also driving incremental improvements in HRSG designs. * Significant efficiency enhancement can be gained in retrofit/upgrades of old generation steam turbines (opportunity here - in US, more than 1300 major steam generating plants over 30 yrs old!) * New blade designs, new coatings offer significant enhancements - efficiency improvements of up to 10% claimed by vendors. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 15 Emerging Technologies * Tremendous interest being created by socalled "micro-turbines," and by fuel cell advances. Some debate as to classification of microturbine, but rough characteristics: * power range of 10 kW to 500 kW; * turbomachinery based on radial flow designs, often derived from automotive turbocharger technologies; * usually just one rotating unit, with compressor, power turbine, and generator all on common shaft; IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 16 * high speed operation, 10,000 to 100,000 rpm; * modest pressure and temperature operation, yielding fairly low emission (catalytic converters can be added); * very compact construction, suitable for transport by small truck; * generator allowed to operate at variable speed, at high frequency, into power electronic rectifier and internal DC bus, inverted to grid frequency AC. IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 17 Questions: * Will units achieve low maintenance, "turnkey" operation desired for target markets? * Cost, efficiency, and cumulative environmental impact of large numbers of these units? * Interconnection standards, and impacts on grid stability and reliability? IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 18 Fuel Cell Technologies * Growing experience with test installations - fuel cells in use in some reliability critical backup applications (e.g. Citibank, NYC), as well as US military test sites. * Very high capital cost remains key barrier to market acceptance. * Some analysts see possibility of price reductions coming from "spillover" automotive developments - major auto manufacturers placing large R&D budgets on fuel cells. However, significant difference in thermal management challenges for mobile vs. stationary power. * Technical applications questions for grid application - similar to microturbines - IMA Tutorial: Electric Power Grids Minneapolis, MN, March 7, 2004 C. L. DeMarco, University of Wisconsin-Madison; page 19 what should be the interconnection standards? what are units’ dynamic