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Energy Storage Systems For
Advanced Power Applications
Paulo F. Ribeiro, Ph.D., MBA
[email protected]
Calvin College
Grand Rapids, Michigan, USA
Energy Storage
Energy is a Life Sustainable Business
•Sustainability
Efficiency
Performance
Conservation
Renewable Sources
•Present socio-economic realities – limits developments
•Better Understanding of Performance Issues is Needed
Abstract
Energy storage technologies do not represent energy sources
Provide valuable added benefits to improve:
stability, power quality and security of supply.
Battery Technologies
Flywheel Technologies
Advanced / Super Capacitors
Superconducting Energy Storage Systems
Introduction
•Electric Power Systems - Experiencing Dramatic Changes
•Electric load growth and higher regional power transfers in a largely interconnected network:
>>complex and less secure power system operation.
•Power generation and transmission facilities - unable to meet these new demands
•Growth of electronic loads has made the quality of power supply a critical issue.
•Power system engineers facing these challenges - operate the system in more a flexible.
•
•In face of disturbances - generators unable to keep the system stable.
•High speed reactive power control is possible through the use of flexible ac transmission systems
(FACTS) devices.
•Better solution: rapidly vary real power without impacting the system through power
circulation.
•
•Recent developments and advances in energy storage and power electronics technologies
Energy Storage Systems for Advanced Transmission and
Distribution Applications
•Energy Storage Technology – Power Convert
•Factors:
The amount of energy that can be stored in the device.
The rate at which energy can be transferred into or out of the storage device.
•Power/Energy ranges for near to mid-term technology have projected
•Integration of energy storage technologies with Flexible AC Transmission
Systems (FACTS) and custom power devices are among the possible advanced
power applications utilizing energy storage.
Power vs. Energy Ranges
for Near to Midterm Technology
SMES
Power (MW)
100
10
Capacitor
Flywheel
Batteries
1
1
10
Energy
(MWsec)
100
1000
Benefits: transmission enhancement, power oscillation damping,
dynamic voltage stability, tie line control, short-term spinning reserve,
load leveling, under-frequency load shedding reduction, circuit break
reclosing, sub-synchronous resonance damping, and power quality
improvement.
Source ASA
A. Superconducting Magnetic Energy Storage (SMES)
AC
Line
Transformer
Power Conversion System
CSI
or
VSI + dc-dc chopper
Bypass
Switch
Dewar
ICoil
Coil
VCoil
Cryogenic
System
Controller
Coil Protection
A. Superconducting Magnetic Energy Storage (SMES)
A. Superconducting Magnetic Energy Storage (SMES)
Solenoid Configuration
(100 MJ – 4kA - 96MW System)
A. Superconducting Magnetic Energy Storage (SMES)
SMES’ efficiency and fast response capability (MW/millisecond) have been, and
can be further exploited in applications at all levels of electric power systems.
Potential applications have been studied since 1970’s.
a) load leveling,
b) frequency support (spinning reserve) during loss of generation,
c) enhancing transient and dynamic stability,
d) dynamic voltage support (VAR compensation),
e) improving power quality,
f) increasing transmission line capacity, thus enhancing overall security and
reliability of power systems.
Further development continues in power conversion systems and control schemes,
evaluation of design and cost factors, and analyses for various SMES system
applications..
A. Superconducting Magnetic Energy Storage (SMES)
Power (MW)
Dynamic Response
Generation
10,000
Frequency
Control
1,000
Voltage/VAR
Transmission
100
10
Cy
1
Se c
0.1
c
le s
Se c
rs
Hou
rs
Hou
s
ute
Min
s
ond
s
r
Hou
o
t
utes
Min
Load Leveling
Generation
Load Leveling
Transmission
s
our
to H
s
e
ut
Min
le s
s
ond
Load Leveling
Distribution
Power
Quality
1
s
ond
Stability
Transmission
Custom
Power
Cyc
Se c
Spinning
Reserve
10
MWs
100
1,000
1
10
100
1,000 10,000
MWhr
Energy
Energy-power characteristics for potential SMES
applications for generation, transmission, and distribution.
B. Battery Energy Storage Systems (BESS)
Batteries are one of the most cost-effective energy storage
technologies available, with energy stored electrochemically.
Key factors in battery for storage applications include: high energy
density, high energy capability, round trip efficiency, cycling
capability, life span, and initial cost.
Battery technologies under consideration for large-scale energy
storage.
Lead-acid batteries can be designed for bulk energy storage or for
rapid charge/discharge.
Photo Source: UP Networks
Mobile applications are favoring sealed lead-acid battery technologies
for safety and ease of maintenance.
Valve regulated lead-acid (VRLA) batteries have better cost and
performance characteristics for stationary applications.
BESS Example – Transmission/Distribution Application
Lead-acid batteries,
have been used in a
few commercial and
large-scale energy
management
applications.
The largest one is a 40
MWh system in
Chino, California,
built in 1988. The
table below lists and
compares the leadacid storage systems
that are larger than
1MWh.
C. Advanced / Super / Capacitors
•The amount of energy a capacitor is capable of storing can be
increased by either increasing the capacitance or the voltage
stored on the capacitor.
•The stored voltage is limited by the voltage withstand
strength of the dielectric.
•As with batteries, the turn around efficiency when
charging/discharging capacitors is also an important
consideration, as is response time.
•The effective series resistance of the capacitor has a
significant impact on both. The total voltage change when
charging or discharging capacitors is shown in equation
q = CV
C=
eA
d
1
=
E
CV 2
2
dV = i *
dt
+ i * Rtot
Ctot
C. Advanced / Super / Capacitors
NESSCAP 10F/2.3V
C. Advanced Capacitors
Advantages
Disadvantage
Power (higher density)
Energy Efficiency (higher)
Maintenance
Discharge
Energy Density
Parameters
Discharge
Charge
Energy Density
Power Density
Charge Eff.
Cycle life
Ness Caps
Electrostatic Cap
10E-3-6 sec
10E-3-6 sec
<0.1 Wh/kg
>10E4Wh/kg
~1.0
infinite
Ultra-Cap
1-30 sec
1-30 sec
1-10Wh/kg
10-20E4Wh/kg
0.9-0.95
>500,000
Battery
0.3-3 hours
1-5 hours
20-100Wh/kg
5-200Wh/kg
0.7-0.85
500-2000
D. Flywheel Energy Storage (FES)
Flywheels can be used to store energy for power systems when the
flywheel is coupled to an electric machine.
Stored energy depends on the moment of inertia of the rotor and
the square of the rotational velocity of the flywheel.. Energy is
transferred to the flywheel when the machine operates as a motor
(the flywheel accelerates), charging the energy storage device. The
flywheel is discharged when the electric machine regenerates
through the drive (slowing the flywheel).
Active Power, Inc.
E=
1 2
2I
I=
r 2mh
2
The energy storage capability of flywheels can be improved
either by increasing the moment of inertia of the flywheel or
by turning it at higher rotational velocities, or both.
The moment of
inertia (I)
depends on the
radius, mass,
and height
(length) of the
rotor
D. Flywheel Energy Storage (FES)
Flywheel energy storage coupled to a
dynamic voltage restorer.
=
=
FW
Example – End-User Application
Energy Storage / UPS Systems
Manufacturer
Technology
Capacity (kW)
Capacity (time)
A
Flywheel
120 kW
20 sec
B
Flywheel/Battery
160 kW
15-30 min
C
Battery
3.1 - 7.5 kVA
15 min
Battery
0.7 - 2.1 kVA
10 min
Battery
700 - 2100 kVA
13 min
Battery
7.5 - 25 kVA
17 min
Battery
1250 kVA
15 min
Flywheel
700 kW
10 min
E
Battery
450 - 1600 kVA
6-12 min
F
Flywheel/Battery
5-1000 kVA
5-60 min
G
Battery
0.14 - 1.2 kVA
5-59 min
H
Battery
0.28 - 0.675 kVA
15 min
D
Source: EPRI
Advanced Power Systems Applications
SMES can inject and absorb power rapidly, but battery and flywheel systems are modular and more
cost effective. Advanced flywheels and advanced capacitor technologies are still being developed
and are emerging as promising storage technologies as well.
SMES
Performance \ ESS
BESS
FES
Advanced
capacitor
Dynamic Stability
Needs to be
explored
Transient Stability
Voltage Support
Area
Control/
Regulation
Frequency
Transmission Capability
Improvement
Power Quality Improvement
A. Integration of Energy Storage Systems into FACTS Devices
FACTS controllers are power electronics based devices that can rapidly influence the transmission
system parameters such as impedance, voltage, and phase to provide fast control of transmission or
distribution system behavior.
FACTS controllers that can benefit the most from energy storage are those that utilize a voltage
source converter interface to the power system with a capacitor on a dc bus. This class of FACTS
controllers can be connected to the transmission system in parallel (STATCOM), series (SSSC) or
combined (UPFC) form, and they can utilize or redirect the available power and energy from the ac
system.
Without energy storage, FACTS devices are limited in the degree of freedom and sustained action
Device
MVA
Real Power
from SMES
FACTs Device
Reactive Power (Q)
Converter Losses
A. Integration of Energy Storage Systems into FACTS Devices
Steady State
Issues
Voltage Limits
Thermal Limits
Angular Stability Limits
Loop Flows
Dynamic
Issues
Traditional Solutions
Breaking
Resistors Load
Shedding
Fixed
Compensation
Line
Reconfiguration
Better
Protection
Increased
Inertia
Advanced Solutions
FACTS
Energy Storage
Transmission
Link
FACTS
Devices
Transient Stability
Damping Power Swings
Post-Contingency Voltage
Control
Voltage Stability
Subsynchronous Res.
Enhanced
Power Transfer
and Stability
SVC
STATCOM
TCSC, SSSC
UPFC
A. Integration of Energy Storage Systems
Energy Storage for
Generation
Transmission
Distribution
End-User
Functions
Spinning Reserve
Load Leveling
Transmission Cap.
Reliability
Stability
Continuity
Reliability
Power Quality
Power Quality
Configurations
Shunt Comp.
Shunt / Series Comp.
Shunt / Series Comp.
Shunt Comp.
Applications
FACTS Devices
Statcom
PQ Parks
Arc Furnace
STATCOM with SMES
STATCOM with SMES
STATCOM/SMES dynamic
response to ac system oscillations
The performance of a power-electronics energy-storage-enhanced device is very
sensitive to the location with regard to
generation and loads, topology of the supply
system, and configuration and combination of
the compensation device.
STATCOM with SMES
Location and Configuration Type Sensitivity
No Compensation
60.
8
59.
2
time (sec)
2 STATCOMs
1 STATCOM + SMES
60.
8
60.
8
59.
2
59.
2
time (sec)
Voltage and Stability Control
(2 x 80 MVA Inverters)
time (sec)
Enhanced Voltage and Stability Control
( 80 MVA Inverter + 100Mjs SMES)
1
S
FACTS with BESS
R1
1
R2
2
E x te rn a l
E x te rn a l
P o we r
Bu s 1
P o we r
Bu s 2
S 3
2S
S
4
C retlif
C retlif
L
retlif
B a te ry
C d c1
C
d c2
_
+
S ix C o n tro l
S ig n a ls
M e a s u re d
V a lu e s
P CD
- S P -b a s e d
c o n tro sl y s te m
S ix C o n tro l
S ig n a ls
R e ef re n c e
V a lu e s
FACTS with BESS
(a) active power from 50W to 400 W
(b) reactive power from 755Var to 355Var
Predicted and experimental response of the SSSC/BESS
FACTS with BESS
(a) STATCOM vs
STATCOM/BESS
(b) SSSC vs SSSC/BESS
Active power flow between areas
(c) STATCOM/BESS vs
SSSC/BESS vs UPFC
FACTS with BESS
(a) STATCOM vs
STATCOM/BESS
(b) SSSC vs SSSC/BESS
Voltage at Area 2 bus
(c) STATCOM/BESS vs
SSSC/BESS vs UPFC
Each 10kW -1.5 MW
AC
LOAD
AC
Infeeds
B. Advanced HVDC Transmission
and Distribution
DC
AC
LOAD
Bus
AC
LOAD
AC
LOAD
= =
Improvements in power electronic device
technologies have led to significant improvements
in the flexibility of dc transmission systems through
the ability to use voltage source converters.
Traditional direct current systems see limited use as
high power, high voltage dc (HVdc) transmission
systems.
Advanced dc systems allows lower voltage dc
transmission system capable of supporting a large
number of standard “off the shelf” inverters.
Energy storage can be added to the dc system,
providing improved response to fast load changes
drawn by the inverters.
DC system with capacitive energy storage added
to the dc system through a dc to dc converter.
C. Power Quality Enhancement with Energy Storage
Custom power devices address problems found at distribution level, such as
voltage sags, voltage swells, voltage transients and momentary interruptions.
The most common approaches to mitigate these problems focus on customer
side solutions such as Uninterruptible Power Supply (UPS) systems based on
battery energy storage.
Alternative UPS systems based on SMES and FESS are also available.
=
=
=
Dynamic voltage restorer (DVR) with capacitor storage
FACTS + Energy Storage
Q
The Role of Energy Storage: real
power compensation can
increase operating control and
reduce capital costs
MVA Reduction
The Combination or Real
and Reactive Power will
typically reduce the Rating of
the Power Electronics front
end interface.
Real Power takes care of
power oscillation, whereas
reactive power controls
voltage.
STATCOM
Reactive Power Only
Operates in the
vertical axis only
P
P - Active Power
Q - Reactive Power
STATCOM + SMES
Real and Reactive Power
Operates anywhere within the
PQ Plane / Circle (4-Quadrant)
Power Electronics - Semiconductor Devices
Decision-Making Matrix
System
VSI
CSI
Commutation
Approach
Natural
Forced
Switching
Technology
Synchronous
PWM
Transition
Approach
Hard
Soft
Circuit
Topology
Two-Level
Multi-Level
Device
Type
SCR
GTO
IGBT
MCT
MTO
Universal Topology + Energy Storage Implementation
E2 / 2
P&Q
E1 / 1
I
X
Plus Energy Storage
Regulating Bus Voltage + Injected
Voltage + Energy Storage
Can Control Power Flow Continuously,
and Support Operation Under Severe
Fault Conditions (enhanced performance)
Cost Considerations
Energy storage system costs for a transmission application are driven by the
operational requirements.
The costs of the system can be broken into three main components:
The energy storage system,
The supporting systems (refrigeration for SMES is a big item) and
The Power Conversion System.
The cost of the energy storage system is primarily determined by the amount of energy to be
stored. The configuration and the size of the power conversion system may become a
dominant component for the high-power low-energy storage applications. For the utility
applications under consideration, estimates are in the range of $10-100K per MJ for the
storage system.
Cost Considerations
In order to establish a realistic cost estimate, the following steps are suggested:
· identify the system issue(s) to be addressed;
· select preliminary system characteristics:
· define basic energy storage, power, voltage and current requirements;
· model system performance in response to system demands to establish
effectiveness of the device;
· optimize system specification and determine system cost;
· determine utility financial benefits from operation;
· compare system’s cost and utility financial benefits to determine adequacy of
utility’s return on investment,
· compare different energy storage systems performance and costs
Technology & Cost Trends
$
I
$$$
$
I
additional cost savings possible
Conclusions
Potential performance benefits produced by advanced energy storage
applications:
•improved system reliability
•dynamic stability
•enhanced power quality
•transmission capacity enhancement
•area protection, etc..
FACTS (Flexible AC Transmission Systems) devices which handle both real and
reactive power to achieve improved transmission system performance are multiMW proven electronic devices now being introduced in the utility industry. In
this environment, energy storage is a logical addition to the expanding family of
FACTS devices.
Conclusions
•As deregulation takes place, generation and transmission resources will be
utilized at higher efficiency rates leading to tighter and moment-by-moment
control of the spare capacities.
•Energy storage devices can facilitate this process, allowing the utility
maximum utilization of utility resources.
•The new power electronics controller devices will enable increased utilization
of transmission and distribution systems with increased reliability.
•This increased reliance will result in increased investment in devices that
make this asset more productive.
•Energy storage technology fits very well within the new environment by
enhancing the potential application of FACTS, Custom Power and Power
Quality devices.