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© 2016 Electric Power Research Institute, Inc. All rights reserved.
Mobolaji BelloPower System Studies
August 29, 2016
Micro grid design: Considerations & interconnection studies
2© 2016 Electric Power Research Institute, Inc. All rights reserved.
Outline
Process
work
aroundKey areas
of interest
Use cases
& analytics
tools
Summary
Microgrid
overview
3© 2016 Electric Power Research Institute, Inc. All rights reserved.
Microgrid overview
• Are DERs able to regulate the voltage and frequency within the island?
• Any issues with parallel grid operation?• How is re-synchronization checked
against criteria such as out-of-phase, large change in voltage?
Are existing telemetry / tele-control/ metering adequate?
• Are the fault contributions from DERs sufficient to allow satisfactory operation of protection systems?
• Are existing protection schemes adequate?
Plan, design, operate, control, monitor and optimize seamlessly
Microgrids And obviously many more…..
• Black starting
• Reliability
• Etc.
4© 2016 Electric Power Research Institute, Inc. All rights reserved.
Microgrid Detailed Technical Design
Microgrid Project Objectives
Design Basis and Rationale
Performance Criteria
Site Descriptions
• Electrical & Thermal Needs• Generation Assets• Critical Load Needs• Power Distribution Equip.
DER & Microgrid Controller
Codes & Standards
Control NeedsCommunication Needs
5© 2016 Electric Power Research Institute, Inc. All rights reserved.
DER Characterization
Renewables ▪ Solar Photovoltaics
▪ Solar Thermal
▪ Wind
Fossil Fuels Tech ▪ Boiler
▪ Fuel Cell
▪ Microturbine
▪ NG Genset
▪ Diesel (backup)Energy Storage
▪ Electrical (Power, Energy)
▪ Thermal (Chiller, Refrig.)
Thermal Tech ▪ Heat Pump
▪ CHP
▪ HVACR
▪ Solar Thermal
Other
▪ Electric Vehicles
Electric Storage• Aggregate capacity of all units (kwh)
• Maximum charge rate
(fraction of total capacity charge in one hour)
• Maximum discharge rate
(fraction of total capacity discharge per hour)
• Minimum state of charge
• Charge efficiency
• Discharge efficiency
• Decay/self-discharge (fraction of total capacity per hour)
----------------------------------
• Fixed cost ($)
• Variable Cost ($/kw or $/kwh)
• Lifetime (years)
• O&M fixed costs ($/year)
Solar Photovoltaics• # of modules
• Module rating (kW DC)
• Module Size (m2)
• Efficiency (%)
• Inverter size (kW AC)
• Total land area (m2)
----------------------------------
• Capital cost ($)
• Lifetime (years)
• O&M fixed costs ($/year)
• O&M variable costs ($/year/kW)
Microturbine• Max Power (kW)
• Sprint capacity (% of power)
• # of sprint hours (hours)
• Fuel type
• Efficiency (ratio)
• CHP capable? (yes/no)
• Alpha (power to heat ratio)
• NOx emissions rate (kg/hr)
• Maximum annual operating hours (hours)
• Minimum loading (% of power)
----------------------------------
• Capital cost ($)
• Lifetime (years)
• O&M fixed costs ($/year)
• O&M variable costs ($/year/unit)
• NOx treatment costs ($/kg)
Electric Vehicles• Multiple locations
• Min connect/disconnect SOC
• Max charge hours
• Battery size
• Efficiency
• Decay
• etc.
t
Connect
Disconnect
SOC
6© 2016 Electric Power Research Institute, Inc. All rights reserved.
Data Collection Modeling Impact studiesCommissioning
& operation
Process
o Compliance with protocols
o Model validationo Submission of
modelso Real time ops &
monitoring
o Network models
•Load types
•DER types
•Operation topology
o Protection info
o Scenarioso Clear SOWo Model validationo Grid impact studies
o Steady stateo Fault analysiso Protection
coordinationo Stability studies
7© 2016 Electric Power Research Institute, Inc. All rights reserved.
Design Analysis
volta
ge
time
limits
unacceptableovervoltage
Curr
ent
Impedance
Relay desensitization
Watt
s
Impedance
Load Only
Load and PV
Ener
gy
Time
unserved energy
Energy exceedingnormal
Design Analysis Approach
Load Analysis
Protection & Reliability
DER Sizing & Design
Distribution System Modeling, Simulation & Optimization
Microgrid Controller Architecture & Design
case by case look needed
Location √no impact
Location XPotential risk
• Steady State load flow
• System Dynamic
• Harmonics
• Flicker
• Controls
• Operation seq.
• Fault Current
• Black Start
8© 2016 Electric Power Research Institute, Inc. All rights reserved.
Key interests
• Is the micro grid gen(s) is enough to support the islanded load? • Verify compliance to planning & voltage stability requirements
Load flow
• Is existing protection adequate?• If not, try various options
Protection analysis
• Events (loss of large load, load step & fault clearing capabilities)• Fault Ride Through capabilities of various inverter-based DERs
Dynamic studies
9© 2016 Electric Power Research Institute, Inc. All rights reserved.
Dynamic studies
Grid connected - all DERs in parallel
Separation of the µ- grid due to main
grid blackout
Black-starting supplying crucial
loads
Islanded - with ALL gens
Island - with selected gens
Resynchronization
Plant(s) Operation
mode
Use generic models for controllers and protection equipment
10© 2016 Electric Power Research Institute, Inc. All rights reserved.
Use cases: Current projects
ConEd• Highly meshed• Huge fault levels• Balanced• 216V• Various DER scenarios
SCE• Radial• Unbalanced• 12kV• 80 buses/nodes• 39 lines, 12 loads• 1 shunt capacitor
• Directional over current• Analyze more options
• Early stages
• DER-CAM
• Deep dive
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Analytic tools
Steady state, fault
Steady state, fault, dynamic, protection, ALL
Protection
12© 2016 Electric Power Research Institute, Inc. All rights reserved.
Detailed Design Analysis – Tools
Source: LBNL Paper LBNL-6708E
Need to apply a consistent modeling framework
Allow existing models to feed new analysis
PSCAD/EMTP-RV/MATLAB DesignBase
DIGSILENT
PSS/SINCAL
CYMDIST
SynerGEE
Transient DynamicTime-Series
Analysis/Slow Dynamics
Time-Series Analysis/SS
StepsSteady State
All
OpenDSS/Grid Lab D/DEW
Microseconds Milliseconds Seconds Minutes Hours Days
A variety of MC capabilities requires a variety of models to understand
• Performance
• Grid interaction
• System Protection Scheme Impact
13© 2016 Electric Power Research Institute, Inc. All rights reserved.
Available ToolsSoftware Tool Affiliated Org. Tool Type
CYMDIST CYME International T&D Inc. Planning and simulation of distribution networks, including load flow, short-circuit, and network optimization analysis.
DER-CAM Lawrence Berkeley National Laboratory (LBNL)
Techno-economic tool for microgrid design and operation.
DesignBase Power Analytics Broad platform for electrical system design, simulation, and optimization.
EMTP-RV POWERSYS Solutions Power system transients simulation, load flow, harmonics.
EUROSTAG Tractebel Engineering GDF Suez
Power system dynamics simulation; full range of transient, mid- and long-term stability; steady-state load flow computation.
GridLAB-D Pacific Northwest National Laboratory (PNNL)
Distribution system simulation and analysis.
HOMER Homer Energy LLC, National Renewable Energy Laboratory (NREL)
Techno-economic tool for microgrid design and operation.
OpenDSS Electric Power Research Institute (EPRI)
Distribution system simulation and analysis.
PowerFactory DIgSILENT GmbH Power system analysis tool for load flow and harmonics in transmission, distribution, and industrial networks.
PSCAD Manitoba HVDC Research Center
Power system transient simulation, load flow simulation.
PSS/E Siemens Power Technologies International (Siemens PTI)
Load flow, dynamic analysis, and harmonic analysis of utility and industrial networks.
14© 2016 Electric Power Research Institute, Inc. All rights reserved.
Simulation Tools - Comparison
Power Flow, balanced
Power Flow, unbalanced
Short Circuit
Relay Coordination
Arc Flash
Harmonic Analysis
Transient Analysis
Dynamic Analysis
Quasi Steady-State Analysis
EMTP-RV, Simulink, PSCAD
Aspen, Cape
DesignBase, PowerFactory
PSLF, PSS/E
OpenDSS
GridLAB-D
Best choice
Can be done, but not preferred choice
Cannot be done
ToolStudy
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Summary“Microgrids” brings many technical needs: Good PSA tools available
No one-size fits all protection scheme works for all microgrids
Action planContinue testing various protection schemes
Level of dynamic studies details depends on so many factors i.e. gen types, operation philosophy etc.
Best protection scheme depends on microgrid objective
• Network
• Objective
• Scenarios
• Modeling
Grid requirements
Controllability
Monitoring
Reliability
16© 2016 Electric Power Research Institute, Inc. All rights reserved.
Together…Shaping the Future of ElectricityJeff Smith
865.218.8069
Mobolaji Bello
865.218.8005
Arindam Maitra
704.595.2646