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Planning a successful microgrid


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New York’s Reforming the Energy Vision (REV) initiative seeks to fundamentally transform the way electricity is distributed, generated and used across the State. Utilities are being challenged to adapt their business models and distribution infrastructure to meet these new goals. REV also presents an opportunity for utilities to provide their customers with a broader range of services that lead to a more diverse, innovative and resilient energy infrastructure.
A key focus of REV is the transition to local distributed energy platforms including microgrids, which can be operated in conjunction with the grid or independently in emergencies. TRC recentlypresented an educational webinar to help New York’s utilities and other decision makers take action to plan and implement successful microgrids. This presentation covers:
• Basic concepts for developing a microgrid
• Differences from operating within the conventional grid
• Preliminary engineering steps required
• Options for generation sources

The webinar recording is available at

Published in: Engineering

Planning a successful microgrid

  1. 1. Planning a Successful Microgrid January 22, 2015 Bill Moran, Senior Electrical Engineer Mark Lorentzen, Vice President, Energy Efficiency
  2. 2. 2 Today’s Grid Source:
  3. 3. 3 Tomorrow’s Microgrids Georgia Tech, Climate and Energy Policy Lab
  4. 4. 4 TRC Microgrid Team -
  5. 5. A pioneer in groundbreaking scientific and engineering developments since 1969, TRC is a national engineering, consulting and construction management firm that provides integrated services to three primary markets: Energy | Environmental | Infrastructure  Expert problem solvers  100+ U.S. offices London office  3,000+ employees  NYSE: TRR 5 Company Profile
  6. 6. TRC’s Guiding Principles Our Mission ’ creativity, experience, integrity and dedication to deliver superior solutions to ’ f . Our Vision We will solve the challenges of making the Earth a better place to live – community by community and project by project.
  7. 7. ENR Top 500 Design Firms 7 "The energy market growth is inevitable and one of the largest sectors for capital investment. Any design firm working and supporting that market will have a bright future.“ Chris Vincze, CEO, TRC Companies Inc. E32 36 TRC Cos. Inc., Lowell, Mass. Rank 2013 2012 Firm Firm Type
  8. 8. Growth Drivers Reliability | Power Supply | Aging Generation Assets | Regulatory 8  Electrical Transmission, Distribution & Substation Engineering  Energy Efficiency, Demand Response, Renewable Energy, CHP  Communications Engineering Transformation
  9. 9. High-Profile Private Sector Clients 9
  10. 10. Working With All Levels of Government 10 State and Local Federal
  11. 11. 11 Speaker Highlights Bill Moran has over 35 years' experience in electrical power generation and distribution with a focus on the design, construction and operation of large campus type power distribution systems. Bill is the lead technical consultant supporting the development of f ’ Microgrid Grant and Loan Pilot Program. He is a key member of the TRC Microgrid Team, a multidiscipline team of experts assembled to help clients plan, design and build microgrids. William Moran Senior Electrical Engineer TRC Companies, Inc.
  12. 12. 12 • Microgrid development – where to start • Site selection and types of distribution • Load management • Generation sources • Microgrid protection and controls • Grounding Overview
  13. 13. 13 • Multiple critical facilities • Physical location – Critical Facilities and generation all within reasonable walking distance; voltage drop and cost of distribution feeders are considerations • Widely spaced facilities with numerous non-critical sites between will greatly increase cost of microgrid; separating critical and non critical facilities require additional switching equipment and possibly a dedicated circuit • Are all microgrid facilities within a campus, or will power have to cross public roads? • What does the microgrid look like? Microgrid Development – Site Selection
  14. 14. 14 Campus Microgrid Typical campus system has a single owner of all facilities, and is often served from a single utility meter.
  15. 15. 15 Lateral Island Microgrid LEGEND CF = CRITICAL FACILITY NC = NON-CRITICAL FACILITY Fed from a single utility distribution feeder, which also feeds non-critical facilities that are not included in microgrid.
  16. 16. 16 Dedicated Circuit Microgrid LEGEND CF = CRITICAL FACILITY NC = NON-CRITICAL FACILITY Expensive – redundant distribution circuit to connect critical facilities with microgrid generation.
  17. 17. 17 Meet with the utility • Identify feeder(s) to be incorporated into microgrid • Identify primary system voltage and grounding method • Identify critical facilities to be included in microgrid • Obtain DG interconnection requirements • Discuss system hardening and reliability improvements – Undergrounding, loop feeds, automatic sectionalizing Steps to Project Development
  18. 18. 18 Loop Feed Distribution
  19. 19. Features • Redundant circuit path to each facility • Protective relay functionality to isolate system faults • Communication with other loop switches for coordinated operation • Establishes self-healing distribution • Minimizes outages to individual facility 19 Underground Loop Distribution Switch
  20. 20. 20 Meet with Engineering consultants – establish scope of services • Load Study Prerequisite: upgrade metering to provide real time demand data (1 minute interval ideal), 12 months data preferred On Peak: 6AM – 8PM average load Peak load and duration of peak Off Peak: 8PM – 6 AM average load Identify loads that can be time-shifted to off peak • Motor starting study Inventory motors over 1 HP Size of largest motor Motors over 10 HP: consider soft start or at a minimum wye-delta starting (mandatory for inverter based systems) Calculate starting currents for large motors Know expected motor operating schedule and what motors operate concurrently Steps to Project Development
  21. 21. 21 • Load shedding study – Tier 1 Loads (must run, most critical) – Tier 2 Loads – less critical, to be shed short term to preserve spinning reserve capacity – Tier 3 Loads – emergency load reduction to avoid blackout • Short circuit study – Calculate available fault current when grid connected – Calculate available fault current when islanded Engineering Studies
  22. 22. 22 • ANSI/IEEE standard symbols • Point(s) of common coupling shown • Location and type of isolation switch and circuit breaker shown • All protective relay functions shown • Transformer grounding shown • Transformer impedances shown • Meters and metering connections shown One-Line Electrical Diagram
  23. 23. 23 Typical One-Line
  24. 24. 24 Generation selection • Land availability • Environmental considerations • Energy resources – Wind – Solar – River or tidal flow – Fossil fuels • Effect of uncontrolled renewables (wind and solar) de-stabilizes islanded microgrid and creates need for energy storage Steps to Project Development
  25. 25. 25 • Generation must match the load – exactly – Overload= under frequency trip (0.16 seconds response time) – High speed load shedding a necessity • Provisions for peaks (spinning reserve) – Normally 15-20% of operating load – Depends on system load profile • Surge capacity (motor starting) – Reactive power requirements – Voltage control Powering a Microgrid
  26. 26. 26 Generator types • Synchronous – Voltage and current source – Can supply or absorb reactive power • Induction – Current source only – Requires system source of excitation voltage – No voltage control • Inverter – Current source, externally commutated (UL-1741) – Current and voltage source, self commutated – Limited fault current – Limited reactive power capability Powering a Microgrid
  27. 27. 27 Generator characteristics • Base load – slowly changing or fixed output (slow ramp rate) – Lean burn natural gas – Fuel cell – Gas turbine (large) > 5MW – Hydro • Peaking – rapid response to follow system loads – Diesel – Rich burn natural gas – Inverters – Small gas turbines < 2MW Powering a Microgrid Fuel Cells 7 MW Gas Turbine Diesel Generator
  28. 28. 28 Energy Storage • Load and generation smoothing – Short term 0-15 minutes – Flywheel – Battery & inverter • Time shifting – Reserve energy for peaking – Transferring PV generation to dark hours Powering a Microgrid Flywheel 1 MW Battery & Inverter
  29. 29. 29 Operation when grid connected • Frequency controlled by grid • Voltage controlled by grid • Reactive power (VAR) demand supplied by grid • Distributed generation controlled to maintain desired power output (kW) • Higher available fault current, Utility source + Generation Microgrid Controls
  30. 30. 30 Islanded Operation • Frequency must be controlled by microgrid generation • Microgrid must be able to absorb swings in load • Ramp rate of generators becomes an issue • How is load shared among multiple generators? • Isochronous vs. droop governing • Lower available fault current (generator only) – Will likely require different settings for protective relays – Different short circuit coordination requirements – Potentially greater arc-flash requirements (longer clearing times) Microgrid Controls
  31. 31. 31 Protection • Grid connected – Higher available fault currents – Need to identify external vs. internal faults to prevent false tripping – Fast break away from grid on external fault – Tight control of short time frequency and voltage tripping – Provide for low generation voltage and frequency ride through; keep generation on line as long as possible to support grid – Separate from utility to preserve microgrid and generation Protection and Controls
  32. 32. 32 Protection • Island Mode – Lower fault currents may require separate settings – Wider tolerances on frequency and voltage tripping of generation – Coordinate settings with load management controls to shed Tier 2 loads before frequency degrades on overload – Look at downstream devices, may not properly coordinate tripping with lower fault current Protection and Controls
  33. 33. 33 Controls • Grid connected – Generation dispatch – maximize economics, use historical data – Load management – maintain preplanned load preservation scheme using real-time data; always ready for transition to island mode • Island Mode – Generation dispatch • Establish base load capacity • Establish peaking capacity (load following) (frequency regulation) • Start additional generation as needed • Maintaining spinning reserve Protection and Controls
  34. 34. 34 Controls • Island Mode - Load management – Shed Tier 2 (and Tier 3 if required) on transfer to island mode – Restore loads when sufficient generation capacity is on line – Maintain real time list of Tier 2 loads to be shed to preserve microgrid – Activate load shed during system disturbance, restore loads when able Protection and Controls
  35. 35. 35 Controls • Synchronization - Closed transition – Shift generation to frequency and voltage control upon separation from utility – Monitor external grid voltage and frequency for return of normal service (IEEE-1547 five minute delay of retransfer after stabilization) – When ready, adjust microgrid voltage and frequency to match utility source – Close utility tie breaker – Transition generation to grid paralleled mode – Shut down excess generation Protection and Controls
  36. 36. 36 • Primary system grounding when islanded – Delta system • Grounding transformer – Wye system • Generator Grounding – Ground fault current islanded vs. grid parallel – Grounding resistor vs. reactor – Generator step-up transformer – Wye-Wye? • Ground fault currents grid connected vs. island mode Grounding
  37. 37. 37 Microgrid Development • Identify facilities to be served • Consult with utility for feasibility • Identify facility loads • Define physical and electrical boundaries and ownership of distribution and generation Design • Design interconnection and physical layout of Microgrid • Select and locate appropriate generation sources • Design protection system for grid parallel and island modes • Configure load management controls • Obtain Interconnection Agreement with host utility Conclusion
  38. 38. Questions? Mark Lorentzen P: 607.330.0322 | E: Bill Moran P: 774.235.2602 | E: