Experience with Modular Design in Energy Storage Systems

Itamar Lopes

1

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

3

A1st Design

2nd Design

B C

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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)

4

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

5

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

6

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ampi

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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

7

~ ~ ~ ~ ~= = = = =

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

8

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)

9

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)

10

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

13

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