GRAP Implementation Guide for Municipalities TOPIC 6.3 - MFMA
Microgrids- A Guide for Municipalities
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Transcript of Microgrids- A Guide for Municipalities
www.trcsolutions.com
April 2, 2014
Microgrids: A Guide for Municipalities
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Speakers:
Bill MoranSenior Electrical EngineerTRC Companies, Inc.
Joseph DebsProject Manager, Distributed ResourcesConnecticut Light and Power Co.
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Overview
Microgrid development – where to start
Interconnection
Load management
Generation sources
Microgrid controls and operation
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Microgrid Development – Site selection
Multiple critical facilities
Physical location – within reasonable walking distance
Widely spaced facilities with numerous non‐critical sites interspersed will greatly increase cost of microgrid
Widely spaced facilities with numerous non‐critical sites between will greatly increase cost of microgrid
Are all microgrid facilities within a campus, or will power have to cross public roads?
What does the Microgrid look like?
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Microgrid Development – Site selection
Meet with EDU/MEU
Questions to ask:‐ Are all of the Critical Facilities now served from the same feeder circuit?
‐ What is the primary service voltage?
‐ How difficult (expensive) will it be to isolate these facilities from the rest of the grid?
‐ What portions of the proposed microgrid would be constructed owed and operated by the EDU/MEU?
‐ Will other customers be affected?
‐ What are the historical electrical demand loads for the critical facilities?
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Microgrid Development –Select Engineer/Developer
Qualifications needed:
Prior experience in designing, building microgrid or distributed generation projects
Experienced working with EDU/MEU
Must work closely with host facility and other project stakeholders
Well capitalized
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Microgrid Development –Identify Critical Facility Load
Sources of information: Facility “demand load” information provided by EDU/MEU Check utility bills for “kW demand “
Consider load management: Are all facility loads essential, or can some be shed during
emergency conditions? Do all peak loads occur under the same time or weather
conditions? Can some loads be time‐shifted, i.e deferred to off peak
times (example: water heating, dishwashing etc.)
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Selection of Generation Sources
Efficiency Environment Fuel Source
‐ Non‐interruptible OR‐ 2 week supply
Load following ability Voltage and frequency source
‐ Most inverter based sources not grid independent. Location within microgrid
‐ Central within microgrid preferable‐ Single location preferable to scattered generators‐ Noise and environmental concerns‐ Thermal and other efficiency concerns.
Total generation capacity 120% of critical facility load.
CT landscape and PA 12‐148
"Microgrid" means a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid and that connects and disconnects from such grid to enable it to operate in both grid‐connected or island mode.
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CT Interconnection Rules
Collaborated efforts over the past 10 years on lessons learned
CL&P & UI follow the same process and technical guidelines
Guidelines approved by Public Utility Regulatory Authority (PURA)
Guidelines are based on the Federal Energy Regulatory Commission (FERC) Small Generator Interconnection Process(SGIP) model
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Types of Microgrid
Type 1: Campus Style Microgrid
In this configuration the electrical distribution infrastructure is owned and operated by a single or multiple entities (owner / operator) and does not include islanding of any of the Electrical Distribution Company assets.
– The generator has the ability to island with no interface with the utility Electrical Distribution Company
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Campus style Microgrid
CB
Type of Microgrid
Type 2: Microgrid with Utility Owned Distribution Facilities: In this configuration a portion of the Electrical Distribution Company assets along with selected loads are intentionally interconnected with dedicated generation supplying the loads.
– The generator will need to coordinate with the EDC
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Microgrid with Utility Owned Distribution Facilities:
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The Interconnection Process
Scope: ‐ Scoping Meeting‐ Review for grid connected mode(Normal Interconnection process)
‐ Review of operational procedure (Joint Operation)‐ Review in Island mode will include Protection, voltage, frequency & short circuit impact
‐ Design Electrical distribution system to support Microgrid‐ Design of communication system (SCADA)
Timelines: Depends on complexity of project
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Review of operational procedure
A detailed Operation procedure is required and must consider the following:‐ Operation in grid connected mode‐ Operation in island mode‐ Reconnect to the grid (under direction of EDC)‐ Interlocks (Mechanical and Electrical)‐ Protective Functions in grid and Island mode
Refer to Attachment C for additional information
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Additional Considerations
Manual vs. Automatic operation
Operation and Ownership of grid isolation device(s)
Electrical Distribution Company operating procedures
Maintenance
Cost of upgrades of EDC Facilities (development , installation and operation of Microgrid
Real time communication with EDC (SCADA) if needed
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Basic Understanding
Understanding limitation and possible delays associated with restoration of normal power
Understanding that EDC role is to serve all customers needs including non Microgrid customers, Microgrid should not impact other customers
Upgrades material and practices must be consistent with EDC standard practices to facilitate restoration efforts in event of equipment failure
Define methodology to initiate an island mode Define methodology to return to normal operation
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Successful Application Components
Application Guidelines Fee Complete Application Application Signature Insurance Technical data sheets Number of inverters / Generation Utility account and/or meter number Ownership
‐ Property ‐ Third party ownership of generator
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Successful Application Components
Technical
Exhibit B of the Guidelines
Electrical One‐Line diagram with standard symbols and labels
Timely communication and data transfer
Receive contingent approval prior to construction
Disconnect switch
Compliance with meter and service requirements
Detailed sequence of operation and test plan
Provide detailed relaying information
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Typical One Line
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One‐Line Electrical Diagram
Must be prepared and stamped by a Connecticut Licensed Professional Engineer
Requirements specified in RFP Attachment C‐ ANSI/IEEE standard symbols‐ Point(s) of common coupling shown‐ Location and type of isolation switch shown‐ All protective relay functions shown‐ Transformer grounding shown‐ Transformer impedances shown‐ Meters and metering connections shown
Pillars of a Successful Interconnection
Safety
Reliability Cost
SuccessfulInterconnection
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Island Operation
Voltage control
System voltage must be maintained by generators
ANSI c84‐1
Motor starting
Multiple generator VAR load sharing.
Transfer off/on grid.
‐ Voltage matching
‐ Synchronization
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Island Operation
Control System Frequency
Frequency vs. load control.
‐ Grid Parallel: control generator load
‐ Islanded: control system frequency
‐ Isochronous
‐ Droop
‐ Isochronous load sharing
‐ Load following ability – ramp rate
‐ Parallel generator operation
‐ Effect of uncontrolled renewable sources
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Characteristics of Different Generator Types
Synchronous‐ Voltage and current source‐ Grid parallel or independent
Induction‐ Current source‐ No reactive power (VAR) capability‐ Can not operate grid independent
Inverter‐ Current source‐ Voltage source/self‐commutating‐ UL 1741 compliance
‐ Includes anti‐islanding provisions
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Characteristics of Different Generator TypesPrime mover types
Diesel engine Gaseous fueled reciprocating (Otto cycle)
‐ Rich burn‐ Lean burn
Gas turbine Fuel cell Inverter – PV, Wind etc. Other
‐ Steam turbine‐ Hydro
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Characteristics of Different Generator TypesRamp Rate (Load acceptance)
Load – unload speed
Diesel ‐ 100% block load capable
Inverter with storage – block load capable
Gas turbine 100‐200 kW/second for MW size units
Fuel cells 3‐10 kW/second
Lean burn gas recip. 2‐3 kW/sec. (small units)
Rich burn gas recip. ‐ near block load
‐ 50% ‐ 100% well tolerated depending on manufacturer
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Ways to mitigate slow ramp rates
Load bank‐ Inefficient
Storage‐ Efficient‐ More effective use of generating capacity‐ Expensive‐ Can reduce spinning reserve requirements.
Base load vs. peaking units‐ Slow ramping units operate at nearly constant load‐ Load following done by generators with rapid response
capability‐ Example: base load fuel cells with diesels used for load
following
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Microgrid Controls
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
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Microgrid Controls
Islanded Operation System voltage and frequency controlled by microgrid generation All instantaneous load peaks must be carried by microgrid
generation All VAR demand must be met by microgrid generation
‐ Motor starting is a consideration‐ Elevators‐ Air conditioning equipment‐ Refrigeration/ industrial loads.
‐ Inverters have little ability to handle VAR demand‐ Synchronous generators best able to provide reserve VARs
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Microgrid Controls
Islanded Operation Frequency must be controlled by 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
‐ Will likely require different settings for protective relays‐ Different short circuit coordination requirements‐ Potentially greater arc‐flash requirements
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Microgrid Controls
Load management Spinning reserve 120% of facility load Load peak reduction
‐ Shedding of less critical loads‐ Load shifting‐ Load shedding response ‐ instantaneous (3‐5 cycles)
Contingency management Partial generator loss
‐ Must reduce load immediately to less than 100% of on‐line generation to avoid blackout
‐ Building EMS systems can not react fast enough to reduce load
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Microgrid Controls
Transition control Grid Parallel to Island Operation
‐ Grid tie circuit breaker trips open‐ Excess load shed if spinning generators have less capacity than
load. (high speed load shed)‐ All generators switch from load control to frequency control‐ All generators switch from power factor control to voltage
control‐ Additional generation brought on‐line if needed.‐ Previously shed loads can be restored, if microgrid has full
generation capacity
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Microgrid Controls
Transition control Island Operation to Grid Parallel
‐ Generators adjust to match grid voltage‐ Microgrid frequency and phase angle adjusted to match grid‐ Grid tie circuit breaker closed‐ Generators switch to load (output) control‐ Generators switch from voltage to power factor control‐ Excess generation can be shut down according to normal
operating schedule‐ Any non‐critical loads shed during island operation can be
restored
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Conclusion
Microgrid Development
Identify Facilities to be served
Consult with EDC/MEU for feasibility
Identify Facility loads
Seek developer/engineer
Design
Design interconnection and physical layout of Microgrid
Select and locate appropriate generation sources
Configure load management controls
Obtain Interconnection Agreement
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Conclusion
Construction Purchase and install generation equipment EDC/MEU to construct system modifications to serve microgrid. Construct customer owned distribution and interconnection.
Testing and Commissioning Electrical testing Approval to energize Performance testing Environmental (air) testing Islanding demonstration
Operations Generation in operation Operations management in place Routine maintained scheduled. Annual reports
Questions?Bill Moran, TRC Companies, Inc.P: 774‐235‐2602 | E: [email protected]
DEEP Microgrid program E: DEEP.Energy [email protected]
Joe Debs, Connecticut Light and Power Co.P: 860‐665‐5616 | E: [email protected]
Pat Healy, United Illuminating Co.P: (203) 926‐5257 | E: [email protected]