recent advances in electric energy conversion and storage · pdf file• 3000c switching...
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Recent Advances in Electric Energy
dConversion and Storage
Hamid A. Toliyat, Ph.D., P.E., Fellow of IEEERaytheon Professor
Advanced Electric Machines & Power Electronics (EMPE) LaboratoryDepartment of Electrical & Computer Engineering
Texas A&M UniversityC ll St ti TX 77843 3128College Station, TX 77843-3128
Tel: (979) 862-3034Email: [email protected]
Sources for Electric Power vs. Transport are Distinct Electricity Sent to GridSOURCES USES
Nuclear 8%
Renewables(incl. hydro,
bi i d
Electric PowerSector
39%When you connect the lines, you see
Residential/Commercial
Heat12%
biomass, wind, geothermal,
and solar) 6%Natural
Gas 20%
that there is virtually no overlap between the energy sources used for Electric Power
Industrial Heat &
Process
Imports 3%
Coal 23%Export
Electric Power versus that used for Transportation (oil). This is important when considering “ lt ti ”Process
16%Non-Fuel Petroleum
by-products (asphalt,
petrochemica
Imports
US P t l
Export
“alternative energy” sources.
pls, etc.) 6%US Petroleum
15%
Oil Imports 25%
Transportation27%
Advanced Electric Machines & Power Electronics (EMPE) Lab 2
Source: Lawrence Livermore Natl Labs; EIAData rounded to nearest whole decimal.Sources and Uses less than 1% not included
Energy Losses are Tremendous Electricity Sent to GridSOURCES USES
Nuclear 8%
Electrical System Energy Losses Lost
SOURCES USES
Electric PowerSector
39%
Residential/Commercial
12%
Renewables 6%
Natural Gas 20%
Energy 61%
39%
Industrial
Imports 3%
Coal 23%Export
Energy lost in the process of converting, transporting, & distributing energy is Industrial
16%
Non-Fuel 6%
Coal 23%
ImportsUsefulEnergy
39%Export
g gysignificant; more than 60% of energy input is lost. A 1% decrease could save more than $3.0B annually*.
US Petroleum 15%
Oil Imports 25%
Transportation27%
Advanced Electric Machines & Power Electronics (EMPE) Lab 3
25%* NCI estimate using $50/bbl oil & $3/mmbtu blended cost for gas/coalSource: Lawrence Livermore Natl Labs; EIA2002 Data: Net Resource Consumption ~ 97 QuadsSources less than 1% not included
Energy Issues
Renewable EnergyWave Energy
Photovoltaic Energy
Wi d E
Transportations, Plug‐in Hybrid VehiclesBattery and its Modeling
• Improvement of power density and extension of battery life are strongly required for batteriesWind Energy
Biomass
Geothermal
Hydrogen Fuel Cell
battery life are strongly required for batteries used for HVs, and especially the safe use of Li‐ion batteries is required. From this point of view, the improvement of accuracy in estimating SOC is extremely important.
Motor/Generator and ControlEnergy Storages:
Batteries• Large surface area electrode
• Frequent deep cycles
Motor/Generator and Control• Wide constant power range for traction
• Constant torque for power generation
Inverter and Power Transistors• Cooling and capacitor size
• Low cost integrated system
Flywheels• Higher tensile strength
SMESHi h it t
• 3000C switching devices (Silicon Carbide, etc.)
Energy Harvesting
• Higher capacity current
• Higher temperature superconductor
Ultra capacitors• Higher voltage cells
• Higher reliability
Advanced Electric Machines & Power Electronics (EMPE) Lab 4
Higher reliability
• Lamination of cells and stacks
Energy Harvesting
Exploded view of Seiko Kinetic watch
Advanced Electric Machines & Power Electronics (EMPE) Lab 5
Exploded view of Seiko Kinetic watch
Power Generation with Renewable and Distributed Energy Resources
Advanced Electric Machines & Power Electronics (EMPE) Lab 6
Advanced Electric Machines & Power Electronics (EMPE) Lab 7
Worldwide Wind Growth
Advanced Electric Machines & Power Electronics (EMPE) Lab
Wind As a Percentage of Electricity Consumption
Advanced Electric Machines & Power Electronics (EMPE) Lab
Evolution of Wind Technology
W ld ld t i d ill ( 644A D ) V ti l i i d ill f illi i (S th t I )
Advanced Electric Machines & Power Electronics (EMPE) Lab
World oldest windmill ( 644A.D.), Vertical-axis windmill for milling grain (Southeast Iran)(Deutsches Museum)
source: Wind Turbines book By: Erich Hau
Evolution of Wind Technology (cont’d)
Nacelle with Geared Drive Train and Generator
Advanced Electric Machines & Power Electronics (EMPE) Lab
Electric Machines for Wind Turbines
The three main windThe three main wind turbine designs:
Fi d d ith Past a. Fixed speed with directly grid-coupled squirrel cage generator
Past
b. Variable speed with doubly-fed induction Presentgenerator
c. Variable speed based on a direct-drive system and synchronous generator Future
Advanced Electric Machines & Power Electronics (EMPE) Lab
Commercial Doubly Fed Induction Generator
Advanced Electric Machines & Power Electronics (EMPE) Lab 13
RePower 5MW Machine
Advanced Electric Machines & Power Electronics (EMPE) Lab 14
Low Voltage Ride‐Through Requirement
Advanced Electric Machines & Power Electronics (EMPE) Lab 15
Permanent Magnet Generator (ABB)
Advanced Electric Machines & Power Electronics (EMPE) Lab 16
Drivetrain Possibilities Hub
Mechanical Gear
GridSquirrel-Cage Induction Generator
Hydrodynamic Gear
Mechanically-Controlled
The generator can be coupled to the grid frequency by use of a hydrodynamic gearbox Hub
M h i lGrid
D bl F d
DCAC
DCAC
Excitation Control from Grid
With step‐down gearbox stages, the generator can operate at variable frequency with added power electronics
Di tl d i t bi t
Mechanical Gear
Doubly-Fed Induction Generator
Hub
DCAC
Excitation Control from Grid
Directly‐driven turbines use no step‐down gearbox stages
A magnetic gear would replace step‐down gearbox stages H b AC AC
Singly-Fed Generator
Hub
Mechanical Gear
Grid Wound-Field Synchronous
Generator
down gearbox stages
Problems with traditional gearboxes such as bearings and supplies have been plaguing industry for decades
Hub
Mechanical Gear
DCAC
DC
AC
GridPermanent Magnet
or Squirrel-Cage Induction Generator
H b AC AC
Directly-Driven
HubDC
ACDC
AC
GridPermanent
Magnet Generator
Non-Contact Electromechanical
Advanced Electric Machines & Power Electronics (EMPE) Lab 17
Hub
Magnetic Gear
DCAC
DC
AC
GridGenerator
Motivations for Magnetic Gear Development
(a) DeWind wind turbine with gear (b) a directly driven Enercon wind turbine
Advanced Electric Machines & Power Electronics (EMPE) Lab 18
Permanent Magnet‐Assisted Synchronous Reluctance Machines
Advanced Electric Machines & Power Electronics (EMPE) Lab 19
The Concentric Planetary Magnetic Gear
Two permanent magnet rings with stator pieces in-between to modulate magnetic flux
Advanced Electric Machines & Power Electronics (EMPE) Lab 2020
Modes of Operation
Number of inner pole pairs pi, and stator pieces ns, determine gear ratio [1]
outer-rotor fixed operation fixed stator segment operation
p p pi, p s, g [ ]Either the outer permanent magnet ring or the stator pieces can be fixedOuter-rotor-fixed operation yields a gear ratio of ns/pi
Stator-fixed operation yields a gear ratio of (ns-pi)/pi
Advanced Electric Machines & Power Electronics (EMPE) Lab 2121
Stator fixed operation yields a gear ratio of (ns pi)/pi[1] Atallah, K., Calverley, S., Howe, D., “Design, analysis and realisation of a high-performance magnetic gear,” IEE Proceedings – Electric Power Applications, Vol. 151, Issue 2, pp. 135-143, 2004.
2D Finite Element Analysis
Analysis done in Maxwell 2D finite element analysis packageTwo-rotating bands are simulated in the transient solver type, both
Advanced Electric Machines & Power Electronics (EMPE) Lab 2222
g yp ,having fixed rotational speed for steady-state torque transfer
Selected Models
Number of inner pole pairs pi, and stator pieces ns, determine gear ratio
po/pi
Gear Ratios
Stator Pieces Fixed Outer Rotor Fixed
22/6 3.67/1 4.67/1Outer-rotor-fixed operation yields a gear ratio of ns/pi
Stator-fixed operation yields a ge tio of (n p )/p
22/6 3.67/1 4.67/1
34/6 5.67/1 6.67/1
35/6 5.83/1 6.83/1
31/5 6 2/1 7 2/1gear ratio of (ns-pi)/pi
Gear ratios span from 3.67/1 to 13/113 different models given by
31/5 6.2/1 7.2/1
34/5 6.8/1 7.8/1
22/4 5.5/1 6.5/1
28/4 7/1 8/113 different models, given by the ratio of outer pole pairs to inner pole pairs, are used to simulate 26 different gear ratios
28/4 7/1 8/1
29/4 7.25/1 8.25/1
30/4 7.5/1 8.5/1
31/4 7 75/1 8 75/131/4 7.75/1 8.75/1
20/2 10/1 11/1
21/2 10.5/1 11.5/1
24/2 12/1 13/1
Advanced Electric Machines & Power Electronics (EMPE) Lab 2323
24/2 12/1 13/1
Results
Fixing the outer permanent magnet ring provides a full gear ratio increase over fixed-stator operation
po/piPercent Torque Ripple of Inner Rotor
Stator Fixed Outer Rotor Fixed
22/6 13 92 14 41Percent torque ripple was not detrimental in this change
22/6 13.92 14.41
34/6 10.58 10.93
35/6 1.94 3.01
31/5 3 44 3 5531/5 3.44 3.55
34/5 3.57 3.85
22/4 14.12 13.75
28/4 156.10 155.23
29/4 3.70 3.57
30/4 11.14 17.06
31/4 4.42 3.37
20/2 73.38 72.39
21/2 15.13 15.53
Advanced Electric Machines & Power Electronics (EMPE) Lab 2424
24/2 64.23 64.10
Electromagnetic Gear
Advanced Electric Machines & Power Electronics (EMPE) Lab 25
High Frequency AC/AC Convertersg q y
Introduction
Types of AC/AC Converter:
Indirect AC/ AC ConverterIndirect AC/ AC Convertero DC Link AC/AC Converterso AC Link AC/AC Converters
Direct AC/AC Converter
Advanced Electric Machines & Power Electronics (EMPE) Lab 27
DC Link AC/AC Converter
This type of converter is composed of two back-to-back voltage or current source converters connected via a DC link capacitor or reactor
Two power conversion stages (AC/DC + DC/AC)Rectifier and inverter systems DC t i th d li kDC energy storage in the dc-link
Most ASD in the current market
Advanced Electric Machines & Power Electronics (EMPE) Lab 28
DC Link AC/AC Converter
Diode Rectifier based Inverter (Diode Rectifier+ DC Link+PWM-VSI)
Problems:• High voltage and current stress over device• High dv/dt• Acoustic noise• Highly polluted by harmonics• DC link capacitors are bulky and are usually electrolytic
Advanced Electric Machines & Power Electronics (EMPE) Lab 29
DC Link AC/AC Converter
Back-to-Back Converter (PWM-VSR+DC Link+ PWM-VSI)
• Sinusoidal input/output currentsp / p• Bi-directional power flow• Large DC link capacitor & input inductors required for operation
• Large size and volume• Limited lifetime & limited high temperature operation
The harmonics problem is solved, but other problems still exist here.
Advanced Electric Machines & Power Electronics (EMPE) Lab
p , p
30
DC Link AC/AC Converter
Six step current fed converter
• Requires a relatively large reactor• Dynamic response is slowerDynamic response is slower
Advanced Electric Machines & Power Electronics (EMPE) Lab 31
Direct Conversion
Matrix Converter
Problems:Problems:• Output/input voltage ratio limitation• No input/output Isolation
Advanced Electric Machines & Power Electronics (EMPE) Lab 32
Our Proposed High Frequency AC Link Converter
Novel soft switching ac link converterHigh frequency ac linkIn ac ac case it uses 12 Bi directional SwitchesIn ac-ac case, it uses 12 Bi-directional SwitchesLink is formed by an inductor-capacitor pair (low reactive ratings)Switches are turned on at zero voltageSwitch turn offs are capacitance bufferedLow switching lossesVery compacty p
Advanced Electric Machines & Power Electronics (EMPE) Lab33
Comparing our proposed inverter with some of the existing inverters
Our proposed Kaco Blueplanet 1501 xi Fronius IG inverter series IGp pinverter
pGrid-Tie Inverter 15
http://www ecodirect com/Kacohttp://www.energymatters.com.au/images/fr
Referencehttp://www.ecodirect.com/Kaco-
Blueplanet-1501xi-p/kaco-blueplanet-1501xi.htm
onius/Energy%20Matters%20Fronius%20IG%20inverter%20series%20IG%2015%20-
IG%2060.pdf
Power rating 1.5 kW 1.5 kW 1.5 kW
PriceLess than
$1000$1,429.95 $3,074.00
$1000
Weight 13 lb. (6 kg) 30.8 lbs (14 kg) 19.84 lb (9 kg)
Efficiency 97% 94% 94.2 %
Advanced Electric Machines & Power Electronics (EMPE) Lab 34
Principle of Operation
Link inductor charged using inputs
Charged link discharged to outputsCharged link discharged to outputs
The Inductor Current
Advanced Electric Machines & Power Electronics (EMPE) Lab 35
Principle of Operation
Three input phases and one link to charge
Link charging is split into two Close to unity or desired PF at input
Link discharging is split into two intervals as wellLink discharging is split into two intervals as well.
The sequence and the pairs calculated so as to minimize the partial resonance times while meeting the desired harmonic levels
Advanced Electric Machines & Power Electronics (EMPE) Lab 36
Principle of OperationMode 1 Mode 2
Advanced Electric Machines & Power Electronics (EMPE) Lab 37
Principle of OperationMode 3 Mode 4ode 3 Mode 4
Advanced Electric Machines & Power Electronics (EMPE) Lab 38
Principle of OperationMode 5 Mode 6Mode 6
Advanced Electric Machines & Power Electronics (EMPE) Lab 39
Principle of OperationMode 7 Mode 8
Advanced Electric Machines & Power Electronics (EMPE) Lab 40
Principle of Operation
M d 9 16 h d 1 8 h h li k i d
Advanced Electric Machines & Power Electronics (EMPE) Lab 41
Modes 9-16 are the same as modes 1-8, except that the link current is reversed
Principle of Operation
1st
Power Cycle
Advanced Electric Machines & Power Electronics (EMPE) Lab 42
Principle of Operation
2nd
PowerPower Cycle
Advanced Electric Machines & Power Electronics (EMPE) Lab 43
Applications of the proposed Inverter
Our proposed converter can be used as :
AC‐AC, AC‐DC, DC‐AC, DC‐DC
And the most important applications are:AC drives
S lSolar Inverter
Wind Turbine Inverter
Battery‐Utility Interface
Advanced Electric Machines & Power Electronics (EMPE) Lab 44
Simulation Results
AC-AC (15 kW)
Li k 10 kHLink frequency
10 kHz
Peak Link current
110 A
Link Inductance
140 µH
Link Capacitance
0.2 µF
Advanced Electric Machines & Power Electronics (EMPE) Lab 45
Simulation Results
Advanced Electric Machines & Power Electronics (EMPE) Lab 46
Simulation Results
Advanced Electric Machines & Power Electronics (EMPE) Lab 47
Simulation Results
DC-AC: Solar Converter
Advanced Electric Machines & Power Electronics (EMPE) Lab 48
Simulation Results
Advanced Electric Machines & Power Electronics (EMPE) Lab 49
Simulation Results
Power Reversal
DC/AC We have achieved DC/AC power reversal time of less than 1 ms.
AC/DC
Advanced Electric Machines & Power Electronics (EMPE) Lab
AC/DC
50
Simulation Results
Input Filtered current Input Voltage
Advanced Electric Machines & Power Electronics (EMPE) Lab 51
Simulation Results
Output Filtered current Output Voltagep g
Advanced Electric Machines & Power Electronics (EMPE) Lab 52
Actual Converter
Advanced Electric Machines & Power Electronics (EMPE) Lab 53
Actual Converter results
Low power results
Advanced Electric Machines & Power Electronics (EMPE) Lab 54
Actual Converter results
Link voltage and Link Current
Advanced Electric Machines & Power Electronics (EMPE) Lab 55
Conclusion
The proposed converter is a soft switched high frequency AC link converterThe efficiency is high (around 98%)It is very compactIt is very compactSwitching losses are very small due to the design and control methodThe size of the converter is very compactIt can even be used for power reversal application, and simulations have shown 1ms power reversal time.
Advanced Electric Machines & Power Electronics (EMPE) Lab 56
Flywheel Energy Storage System Fundamentals
Charging Mode of the Flywheel Power in Input electronics Motor Flywheel (stored)
TRp
LriAvA
TAp TBp TCp TSp TTp
uA iRuR
rA
uB
uC
vB
vC
iB
iCTCTBT T TS T
PMSMuS
uT
iS
iT
vRS
vST
C
Flywheel
Line-Side Converter Machin-Side Converter
Cr
TCnTBnTAn TRn TSn TTnT
Advanced Electric Machines & Power Electronics (EMPE) Lab
Discharging Mode of the FlywheelPower out Output electronics Generator Flywheel
57
Comparison of High Speed and Low Speed 2 MW Machines
Height 73” (1.85 m)
Conventional 2MW Machines
Height 73” (1.85 m)
Conventional 2MW Machines
73”(1.85m)
hi h
Weight 11,310 lbs. (5130 kg)
Power Density 0.39 kW/kg (326 kW/m3)
Length 90” (2.28 m)
Weight 11,310 lbs. (5130 kg)
Power Density 0.39 kW/kg (326 kW/m3)
Length 90” (2.28 m)
high
28” Height 28” (0 71 m)
Calnetix 2MW High Speed Machines
Height 28” (0 71 m)
Calnetix 2MW High Speed Machines28
(0.71m) high Weight 1650 lbs. (748 kg)
Power Density 2.67 kW/kg (3770 kW/m3)
Length 53” (1.34 m)
Height 28 (0.71 m)
Weight 1650 lbs. (748 kg)
Power Density 2.67 kW/kg (3770 kW/m3)
Length 53” (1.34 m)
Height 28 (0.71 m)
Advanced Electric Machines & Power Electronics (EMPE) Lab 58
Limiting Geometric Design Considerations
Stored Energy Moment of inertia of the flywheel• Radius
212
E Jω=
• Mass
• Height (length) of the flywheel
The square of the rotational velocity of the flywheel
2
2r mhJ =
Limiting Geometric Design ConsiderationsTip speed ( ) due to the strength of the materialstV r ω=p p ( ) g• Steel constructions: 220 to 240 m/s
• Composite structures: more than 1000 m/s
Rotor dynamic behaviors• The various rotor critical (resonant) speeds
• The ability of the flywheel assembly to avoid or traverse them without failure
Advanced Electric Machines & Power Electronics (EMPE) Lab 599/1/2009
High Speed Flywheel
High Speed FlywheelOperate above 10,000 rpm up to 100,000 rpmA flywheel with a low mass but a highA flywheel with a low mass but a high limit for the mechanical tensionThe flywheel has a compound construction with a strength 5 times higher than steelhigher than steelThe mass moment of inertia, weights and dimensions are relatively smallThe rotor runs in a vacuum and is supported by magnetic bearingssupported by magnetic bearingsThe magnetic bearing requires a second set of bearings for emergencyThe output frequency of the synchronous generator is in the kHzsynchronous generator is in the kHz rangeDue to thermal reasons the rotor has no windingsA drawback is the high price of the
Advanced Electric Machines & Power Electronics (EMPE) Lab 609/1/2009
A drawback is the high price of the system
An Example of Flywheel Energy Storage System (source: VYCON)
Non‐contact fully levitated rotorSecondary Mechanical Bearings for back‐up only
High CycleFull Cycle every 15 minutes
DSP Controlled
140 kW for 15 Seconds
1. Flywheel 4. Flywheel Controller
2. GUI 5. Power Stack
Advanced Electric Machines & Power Electronics (EMPE) Lab 619/1/2009
3. Master Controller 6. Vacuum Pump
Experimental Set up
Advanced Electric Machines & Power Electronics (EMPE) Lab 62