Energy Storage Systems For Advanced Power Applications

Paulo F. Ribeiro, Ph.D., MBA

PRIBEIRO@CALVIN.EDU

Calvin College Grand Rapids, Michigan, USA

Energy Storage

Energy is a Life Sustainable Business

•SustainabilityEfficiencyPerformanceConservationRenewable Sources

•Present socio-economic realities – limits developments

•Better Understanding of Performance Issues is Needed

Abstract

 

Energy storage technologies do not represent energy sourcesProvide 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.

10 100 1000 1 Energy

(MWsec)

Pow

er (

MW

)

Capacitor

SMES

Flywheel Batteries

Power vs. Energy Ranges for Near to Midterm Technology

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.

1

10

100

Storage Technologies Main Advantages (Relative to others)

Disadvantages (Relative to others)

Power

Application Energy

Application

Pumped Storage High Capacity, Low Cost Special Site Requirement

Compressed Air High Capacity, Low Cost Special Site Requirement, Need Gas Fuel

Flow Batteries: Regenesys Vanadium Redox Zinc Bromine

High Capacity, Independent Power and Energy Ratings

Low Energy Density

Metal-Air Batteries Very High Energy Density

Electric Charging is Difficult

Sodium Sulfur (NAS) Battery

High Power & Energy Densities, High Efficiency

Production Cost, Safety Concerns (addressed in design)

Li-ion Batteries High Power & Energy Densities, High Efficiency

High Production Cost, Requires Special Charging Circuit.

Ni-Cad Batteries High Power & Energy Densities, Efficiency

Other Advanced Batteries High Power & Energy Densities, High Efficiency

High Production Cost

Lead-Acid Batteries Low Capital Cost Limited Cycle Life when Deeply Discharged

Flywheels High Power Low Energy density

SMES, DSMES High Power Low Energy Density, High Production Cost

Double Layer Capacitors (SuperCapacitors)

Long Cycle Life, High Efficiency

Low Energy Density

Source ASA

A. Superconducting Magnetic Energy Storage (SMES)

ControllerCoil Protection

CryogenicSystem

VCoil

ICoil

DewarPower Conversion System

CSI or

VSI + dc-dc chopper

Transformer BypassSwitch Coil

ACLine

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)

Energy-power characteristics for potential SMES applications for generation, transmission, and distribution.

10

100

1,000

10,000

1

0.1 1 10 100 1,000 1 10 100 1,000 10,000

EnergyMWs MWhr

Power (MW)

Voltage/VARTransmission

StabilityTransmission

Frequency Control Spinning

Reserve

Dynamic Response Generation

Load Leveling Generation

Load LevelingTransmission

Load LevelingDistribution

CustomPower

PowerQuality

A. Superconducting Magnetic Energy Storage (SMES)

 

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.

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.

Photo Source: UP Networks

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 lead-acid storage systems that are larger than 1MWh.

C. Advanced / Super / Capacitors

CVq

d

AC

2

2

1CVE

tottot

RiCdt

idV

•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

                                                                                                                                                                       

                                                                                  

NESSCAP 10F/2.3V

C. Advanced / Super / Capacitors

Advantages Disadvantage

Power (higher density) Energy DensityEnergy Efficiency (higher)MaintenanceDischarge

Parameters Electrostatic Cap Ultra-Cap BatteryDischarge 10E-3-6 sec 1-30 sec 0.3-3 hoursCharge 10E-3-6 sec 1-30 sec 1-5 hoursEnergy Density <0.1 Wh/kg 1-10Wh/kg 20-100Wh/kgPower Density >10E4Wh/kg 10-20E4Wh/kg 5-200Wh/kgCharge Eff. ~1.0 0.9-0.95 0.7-0.85Cycle life infinite >500,000 500-2000

Ness Caps

C. Advanced Capacitors

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).

E = 21I2 I = 2

r2mh

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.

Active Power, Inc.

The moment of inertia (I) depends on the radius, mass, and height (length) of the rotor

=

=FW

D. Flywheel Energy Storage (FES)

Flywheel energy storage coupled to a dynamic voltage restorer.

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

D 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

Source: EPRI

Example – End-User ApplicationEnergy Storage / UPS Systems

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.

Performance \ ESS SMES BESS FES Advancedcapacitor

Dynamic Stability  

Needs to be exploredTransient Stability

Voltage Support

Area Control/ Frequency Regulation

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

DeviceMVA

FACTs DeviceReactive Power (Q)

Real Powerfrom SMES Converter Losses

A. Integration of Energy Storage Systems into FACTS Devices

Advanced Solutions

Transmission Link

Enhanced Power Transfer

and Stability

Line Reconfiguration

Fixed Compensation

FACTS

Energy Storage

Better Protection

Increased Inertia

Breaking Resistors Load

Shedding

FACTS

Devices

Traditional Solutions

SVCSTATCOMTCSC, SSSCUPFC

Steady StateIssues

Voltage LimitsThermal Limits

Angular Stability LimitsLoop Flows

DynamicIssues

Transient StabilityDamping Power Swings

Post-Contingency Voltage ControlVoltage Stability

Subsynchronous Res.

Generation Transmission Distribution End-User

Energy Storage for

Spinning ReserveLoad Leveling

Spinning ReserveLoad Leveling

Transmission Cap.ReliabilityStability

ContinuityReliabilityPower Quality

Power Quality

Functions

Configurations

Shunt Comp. Shunt / Series Comp. Shunt / Series Comp. Shunt Comp.

Applications

StatcomPQ Parks

Arc FurnaceFACTS Devices

A. Integration of Energy Storage Systems

STATCOM with SMES

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

STATCOM/SMES dynamic response to ac system oscillations

2 STATCOMs 1 STATCOM + SMES

Voltage and Stability Control Enhanced Voltage and Stability Control

Syst

em F

requ

ency

(H

z)

60.8

59.2

time (sec) time (sec)

(2 x 80 MVA Inverters) ( 80 MVA Inverter + 100Mjs SMES)

Syst

em F

requ

ency

(H

z)

60.8

59.2

Syst

em F

requ

ency

(H

z)

60.8

59.2

time (sec)

No Compensation

STATCOM with SMESLocation and Configuration Type Sensitivity

 

FACTS with BESS

+_

E x te rn a lP o w e rB u s 2

E x te rn a lP o w e rB u s 1

R 1 R 2

S 1

S S

S

23

C

C C

fi l te r

d c 1 d c 2

C fi l te r

L fi l te r

4

1 2

B a tt e ry

P C - D S P - b a s ed c o n tr o l s y s t em

R e fe re n ce Va lu e s

S ix C o n t ro lS ig n a ls

S ix C o n t ro lS ig n a ls

M ea s u re dVa lu e s

(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 (c) STATCOM/BESS vs SSSC/BESS vs UPFC

Active power flow between areas

 

FACTS with BESS

Voltage at Area 2 bus

(a) STATCOM vs STATCOM/BESS

(b) SSSC vs SSSC/BESS (c) STATCOM/BESS vs SSSC/BESS vs UPFC

 

FACTS with BESS

B. Advanced HVDC Transmission and Distribution 

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.

Bus

LOADAC

LOADAC

LOADAC

LOADAC

InfeedsDC

= =

Each 10kW -1.5 MW

AC

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

STATCOMReactive Power OnlyOperates in the vertical axis only

STATCOM + SMESReal and Reactive PowerOperates anywhere within thePQ Plane / Circle (4-Quadrant)

P

Q

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.

The Role of Energy Storage: real power compensation can increase operating control and reduce capital costs

P - Active PowerQ - Reactive Power

MVA Reduction

FACTS + Energy Storage

VSI CSI

Natural Forced

Synchronous PWM

Hard Soft

Two-Level Multi-Level

SCR GTO IGBT MCT MTO

System

CommutationApproach

SwitchingTechnology

TransitionApproach

CircuitTopology

DeviceType

Power Electronics - Semiconductor DevicesDecision-Making Matrix

X

E1 / 1 E2 / 2

IP&Q

Plus Energy Storage

Regulating Bus Voltage + Injected Voltage + Energy StorageCan Control Power Flow Continuously, and Support Operation Under Severe Fault Conditions (enhanced performance)

Universal Topology + Energy Storage Implementation

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 multi-MW 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.