Accommodating High Levels of Variable Generation - NERC

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Transmission Planning & Resource Adequacy 3.4. Voltage Stability and Regulation Considerations There are many large metropolitan and populate regions of the South and South Western states of the U.S. where the transmission system has become voltage stability limited due to growing residential load (particularly residential air-conditioning) and economic and environmental concerns pushing generation to be remote from the load centers. A typical solution for these scenarios has been reactive compensation at the transmission level near load centers (e.g. Static VAR Compensation). Locating conventional fossil-fired generation closer to the load centers can potentially mitigate the problem (due to the inherent reactive capability of synchronous generators), however many factors, such as emission constraints, economic reasons (cheaper power can be bought from remote generation if the transmission system is supported by smoothly control reactive support), etc., may preclude the viability of this option. Wind and solar (CSP) resources are typically located remote from load centers (see Figure A in the Executive Summary). This condition further heightens the need to pay careful attention to the issues of voltage stability and regulation. The key conclusion here is, whether due to the advent of larger penetration of variable renewable generation resources (which are typically remote from load centers) or the fact that new conventional generation facilities of any kind, are being located more remotely from load centers, issues related to voltage control, regulation and stability must be carefully considered and the power system must have sufficient reactive power resources (both dynamic and static) to maintain reliability. 3.5. Planning Tools and Techniques The addition of significant amounts of variable generation to the bulk system changes the way that transmission planners must develop their future systems to maintain reliability. Current approaches are deterministic based on the study of a set of well-understood contingency scenarios. With the addition of variable resources, risk assessment and probabilistic techniques will be required to design the bulk power system. One vital goal of transmission planning is to identify and justify capital investments required to maintain power system reliability, improve system efficiency and comply with environmental policy requirements. A transmission planner is required to identify and advance new transmission facilities to maintain system reliability and improve system efficiency by allowing new demand growth to be supplied, managing transmission congestion, and integrating new generation resources, among other reasons. To perform transmission planning, the planner needs to study power flow, time-domain and small-signal stability along with short-circuit duty analyses tools. Accommodating High Levels of Variable Generation 44
Transmission Planning & Resource Adequacy Figure 3.5 illustrates an example of the total wind power distribution in Spain for the years of 2001 through 2005. 61 This figure illustrates that the total wind generation on a power system is rarely at its peak capacity. In this particular example, the median power output is around 27% of the nameplate capacity. That is, the total wind generation is 50% of the time below 27% and 50% of the time above 27% of its capacity. Thus, it is clear that studying wind generation scenarios just at peak output for a variety of load forecast scenarios will not be sufficient as it does not represent a very likely scenario. Addition of variable generation substantially increases the need to investigate many more scenarios in order to ensure bulk power system reliability. 60% 50% 40% 30% 20% 10% 0% 20% 30% 40% 50% 60% 70% 80% 90% 100% Figure 3.5: Wind power distribution for 2001 – 2005 in Spain Traditionally, both transmission and operational planning studies have, for the most part, relied on deterministic reliability criteria and methods, mainly for ease of analysis. The paradigm in today’s power industry is one of separated generation, transmission and distribution entities accentuated by the need to plan for significant penetration of variable resources. These factors render planning based solely on deterministic criteria for system expansion less effective since: 1. The restructuring of the utility business in most regions has made it more difficult to accurately predict the location of new generation facilities and their respective dispatch patterns (i.e. market driven). Consequently it is significantly more difficult to plan for transmission reinforcements on purely a deterministic basis. 2. High penetration levels of renewable generation will mean an added level of uncertainty on generation dispatch levels even when the locations of these renewable generators are 61 CIGRE Technical Brochure 328, Modeling and Dynamic Behavior of Wind Generation as it Relates to Power System Control and Dynamic Performance, Prepared by CIGRE WG C4.601, August 2007 (www.e-cigre.org ) Accommodating High Levels of Variable Generation 45
Page 1 and 2: Special Report: Accommodating High
Page 3 and 4: Table of Contents Table of Contents
Page 5 and 6: Executive Summary Executive Summary
Page 7 and 8: Executive Summary Additional flexib
Page 9 and 10: Introduction 1. Introduction Fossil
Page 11 and 12: Introduction Mindful of NERC’s mi
Page 13 and 14: Introduction In Arizona, the number
Page 15 and 16: Characteristics of Power Systems &
Page 23 and 24: 2.4. Principal Characteristics of W
Page 31 and 32: 2.4.1.3.Summary of Wind Controls Ch
Page 43 and 44: Transmission Planning & Resource Ad
Page 51: Transmission Planning & Resource Ad
Page 63 and 64: Power System Operations In the case
Page 65 and 66: Power System Operations 400 AESO Wi
Page 67 and 68: Power System Operations NERC Action
Page 69 and 70: Power System Operations participati
Page 71 and 72: Conclusions & Recommended Actions 5
Page 73 and 74: Conclusions & Recommended Actions g
Page 75 and 76: Appendix I: 2009-2011 Objective and
Page 83 and 84: Appendix II: Wind-Turbine Generatio
Page 85 and 86: Acronyms Acronyms ACE - Area Contro
Page 87 and 88: Acronyms VRT - Voltage Ride-Through
Page 89 and 90: IVGTF Roster Member William Grant M
Page 91 and 92: IVGTF Roster Observer Sasan Jalali
Page 93 and 94: IVGTF Roster NERC Staff Mark G. Lau
Page 95 and 96: References [15] EoN Netz Wind Repor
Page 97 and 98: References [42] Milligan, M.; Kirby
Page 99 and 100: References [66] GE Energy, Intermit
Page 101 and 102: References [89] Zavadil, R., J. Kin
Page 103 and 104:
References [108] W. Wangdee, R. Bil
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