Experience with Modular Design in Energy Storage Systems
Itamar Lopes
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Modular Energy Storage SystemIncrease of Flexibility, Scalability and Reliability
2
Smart Network Control
System Control
Inverter Control
Data Logging
Battery Management
Battery Bank
Filter
Transformer
AC/DCInverter
Switchgear
2
~= ~= ~= ~= ~= ~= ~= ~= ~= ~=~= ~=1
Modular ApproachConventional Approach
1- Micro Inverters2- Single Battery Rack
Grid Grid
DC Breaker
Two proposed modular designs to attend customer’s need
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A1st Design
2nd Design
B C
~= ~= ~=
A
~= ~= ~= ~=
C
B
Paralleling on AC Side
No Balancing of Batteries
Easy Extension
No “Rotten Apple” Effect
High Availability
Minimum exposure to DC
Integration to any Battery supplier
“Unit Commitment” to generate desired wave form at Point of Interconnection (POI)
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POI
POI
~= ~= ~= ~= ~=
PCU
1 2 3 4 5
1
2
3
4
5
Power Control Unit manipulates each wave form generated by all inverters
Individual 2- Level Inverter Multilevel InverterX n
Conventional DesignModular Design
POI
Modular Design offers higher efficiency during charges and discharges below installed power
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500kVA~
~ ~ ~ ~ ~= = = = =
100kVA
1
2
0 10 20 30 40 50 60
100
95
90
85
80
75
70
2
1
Output Power Level %
Efficiency %
Improvement of efficiency due to modular design
=
During low power operation, a modular system can work on a higher efficiency level than a similar size conventional system.
By shutting off unneeded inverters, the modular system can reduce standby loads and auxiliary power losses (HVAC, etc)
Most applications require quick variation of the E-Storage system output
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Report from a customer…In certain circumstances, the power generation fluctuates from 100% to 40% (Nominal rate) within 30 s
Utility Code…A 10 % per minute rate (based on AC contracted capacity) limitation shall be enforced
Interconnection on AC side prolong system longevity and promote s system enhancement
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~ ~ ~ ~ ~= = = = =
SOC 92% 91% 90% 95% 92%
~ ~= =100% 100% 100%
1
45
+2
1000 Vdc 800 Vdc
Year 0Year 10 6
1 – Possible uneven SOC across batteries2 – Simple increment of power and capacity 3 – Easy implementation of redundancy 4 – Adaptation of different Suppliers /Vdc5 – Possible mix of Technologies6 – Neutralization of uneven aging / internal resistance
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3
Modular design can reduce footprint and increase system safety and availability
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11
2233
44
InverterDC
Breaker
DC Busbar
Compartment Split
Coventional Approach: One Inverter, One DC Breaker, Parallelism on the DC side
55
66
AC Parallelism Single Compartment77
Block Maintenance & Extension88
Compact DC Breaker
Modular Concept : Multiple Inverters & Parallelism on AC side
Modular design : how it operates (1/3)
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Load
Pro
file
Time
Maximum Contractual Power
$/kWh
$$$/kWh
POI
GRID
Load
T= tU
tility
TimeT= t
Bat
tery
POI
GRID
STORAGE Load
Modular design : how it operates (2/3)
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Modular design : how it operates (3/3)
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POI
POI
~ = ~= ~= ~= ~=
PCU
SOC 90% 80% 85% 70% 90%
Inv 1 = 0%Inv 2 = 24%Inv 3 = 26%Inv 4 = 23%Inv 5 = 27%1
2
P Discharge = 500kW
Inv 1 = 0kWInv 2 = 120kWInv 3 = 130kWInv 4 = 115kWInv 5 = 135kW
2
Low Priority3 – Supervision of status of Inverters and Batteries4 – Calculation of contribution of every power string
1
High Priority1 – Total Charge/Discharged is determined3 – Setpoints for every inverter is calculated
Notes on Modular Design Availability: Sample Project
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AB
C
Power Bloc A11,200 kW
Power Block A21,200 kW
Transf A2,400 kW
MV SWGR6,800kW
Container A
MV SWGR6,800kW Power Bloc B1
1,200 kW
Power Block B21,200 kW
Transf B2,400 kW
Container B
Power Bloc C11,200 kW
Power Block C2800 kW
Transf C2,000 kW
Container C
Project Consideration: 6,0 MW65 Power String + 3 Spares
Influence of Communication Equipment failureInfluence of Power Equipment failure
Requirement: 97%
Notes on Modular Design Availability: Sample Project
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Availability 99.55%
To reach 97% the calculated downtime would have to grow by a factor of 6.7 (1,576,800 / 234,840)
BattInv
GC
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
BattInv
Power Block
Lessons Learned from our Experience with ENEL Project1MVA / 500kWh
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ENEL/Italy - Commissioning in February 2012
Multiple HVAC Units
HVAC Split Unit / Wall Mount1
2
Air Duct
HVAC Unit
1 – Single HVAC Condenser
2 – Metal Duct mounted on container ceiling
3 – Water Infiltration due do metal contraction (duct)
4 – Damage of one inverter module. Remaining units into normal operation
Distributed Energy Storage: A “modular approach” to address all System needs
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Renewable Smoothing
Upgrade DeferralCongestion ReliefVoltage Support
Ancillary Services
Frequency Regulation
Resource Adequacy
Renewable Firming
Time Shifting
Bulky Storage Spinning Reserve
Ramping Control
Black Start
Reactive Power
Photovoltaics &concentrated solar power
Wind powerConventional
Generation Transmission Large commercial
ResidentialIndustrial
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*
*
*
Power Quality
Backup Power
Diesel Off-set
Peak Load ManagementDistribution