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Residential Battery Storage: The cornerstone of the
Nanogrid and distributed power systems
Antonio GinartSanta Clara, California
1
Power System Centralized vs. Distributed
Wind Farm
Rural
City
Solar Farm
Power plant
Industry
Rural
City
Industry
Distribution
Distributed Paradigm Shift - Renewables
Disadvantages More complex technologiesMore expensive in many casesLess centralized controlPotential for a less reliable gridNeed of new technology and
regulationsPotential for greater power
quality issues
Advantages Potential for better local resource useConsumers have greater
independence Environmentally friendlier Potential for a more robust and
reliable grid (non-single collapse point)CybersecurityNatural disaster
Potential for more economically sound macro-analysis
3
http://www.forbes.com/sites/erikkain/2012/06/27/wildfire-burns-homes-in-colorado-springs/http://www.forbes.com/sites/erikkain/2012/06/27/wildfire-burns-homes-in-colorado-springs/http://www.usatoday.com/story/weather/2013/09/14/boulder-colorado-floods/2813225/http://www.usatoday.com/story/weather/2013/09/14/boulder-colorado-floods/2813225/
Minimum-cost of Electrification Electrification Model (REM)
400,000 non-electrified buildings in the Vaishali district of Bihar, India.
Options
Grid extension (low-voltage lines) Stand alone system (Nanogrid)Microgrid
MIT News (January 2016)4
Nanogrid Operation Mode
Grid-Tied• Frequency
• VoltageBack-upIslanding
Reliability
Independence
Solar Autonomy:
Germany 60%USA 100%
Power PG= Pload
Control Stability
Volt. Freq. Droop
• Load Criticality
• Load sink• Load dumping
Fixed voltage and frequency
TransferSwitch
Fast Low cost
Power
Power
Tariff• Zero export
• Peak demand• Sell/Buy price
Power Quality Flicker
SagSwell
Control Load
Generation5
Power Quality Issues (Back up Mode) Voltage
Clipped current100A peak
Voltage sag
Voltage swell
The standard IEEE 1100• Short term voltage variations (sag ,swell, and transients)• Long term voltage variations (over and under voltages ,
harmonics and noise)
Line voltages under A/C 5 TON system start up
½ cycle8.3ms
1 cycle16.6ms
3600 cycles60 s
>3600 cycles> 60 s
1Transients
2Sag and swell
3 Noise4 Harmonics
5 Under andover Voltages
6
Residential Nanogrid DC-AC
• 12V- 400V • Advantages
• More efficient • Easy control, stable
• Disadvantages• Large investment required• Difficult interruption
(protection, fire)
• Advantages• Required no additional
investment• Easy retrofit
• Disadvantages • Control and stability are
more difficult• Region dependent
• 200-230V 50Hz• 120/240V 60 Hz US
DC Nanogrid AC Nanogrid
7
Basic DC and AC Nanogrids: Solar and Energy Storage
GRID
AC
DC
DC
DC
Bi-directional
Batteries
PV panel Inverter
Bi-directional
GRID
AC
DC
AC
DC
Bi-directional
Batteries
PV panel Inverter
Inverter
DC Nanogrid
DC
AC
AC Nanogrid
AC
8
DC Residential Nanogrid
GRID
AC
DC
Bi-directional
Batteries
PV pannel
Inverter
DC
DC
DC
DC
DC 380VDC
DC
DC
DC
DC
DC
DC
DCBi-directional
DCDC
DC
E or H car
Wind
Generator
DC
DC
DC
AC
Bi-directional
DC 380V9
DC Residential Nanogrid- Control Droop Voltage Control
Bus Voltages
V0V1V2
A B
Current
Source 1
Constant PowerConstant Voltage
PL1 PS1PL1
PL2
State 1
State 2
Overload
DC
DC
DCDC
DC
DC
DC
DCDC
DC
DC
AC
Renewable
Non-Renewable
Co1
Co1
DC BusMPPT
Load
Power
P1
P1
10
Schönberger, J., Duke, R. and Round, S.D., 2006. DC-bus signaling: A distributed control strategy for a hybrid renewable nanogrid. Industrial Electronics, IEEE Transactions on, 53(5), pp.1453-1460.
Control Example
AC Residential Nanogrid
DieselGas
Stirling
GeneratorsEnergy Storage
MasterController
Solar
DCAC
Wind
Renewable Generators
Transfer switch
@
Control Droop Control Voltages and Frequency
Residential Load
Washer DryerRange Water
HeaterA/CUnit
TVComputer Lighting
Fridge
~Grid
11
Load Handling and Criticality
Residential Load
Range WaterHeater
A/CUnit
Microwave
- Critical Loads +
Washer Dryer Lighting
v
MasterController
@
DumpLoadFridge
TV
Z-Waves
12
13
Droop AC control ( Inverter)
The Bode plots of the output impedance of InvertersL-inverter (with L = 7 mH, R = 0.1Q, and Co = 0 µF)R-inverter (with L = 7 mH, R = 8Q, and Co = 0 µF)C-inverter (with L = 7 mH, R = 0.1Q, and Co = 161 µF).
DC LINK
+
-
FilterInverter
~
Battery / solar
DC
DC
DC/DCConverter
Impedance Inverter
14
Droop AC control
iii QnEE −*~
iii Pn−*~ ωω
QiQ*i
*E
*ω
iP*iP
Assuming δ∼0 and Inductive
δ0
0~Z
EVP0
20
0
0~ZV
ZEVQ −
δ~P EQ ~
Universal Droop Control of Inverters
15
Zhong, Qing-Chang, and Yu Zeng. "Universal Droop Control of Inverters with Different Types of Output Impedance."
Droop controllers for L-, R-, C-, RL-, and RC-inverters.
FundamentalsBack up battery storage
Energy Storage (Why Battery & Capacitor?)
Air CompressorHydraulicsThermal (Molten Salt) Inertia Wheels MagneticsCapacitor (Super)BatteryFlow Batteries
Dynamic Power Compensation (very fast – few milliseconds)Sized according its nanogridAble to regulate the nanogrid Weather prediction via internet
DC LINK
+
-
FilterInverter
Grid
~
Transformer
Battery
DC
DC
DC/DCConverter
Storage Power Conversion @
17
Time responses
18
DC Bus
Battery
AIR
Generators
Intermittent Power Power
Fast Energy Storage
19
Ultra-capacitorElectrolytic capacitor
BatteryElectrolyte
Dielectric
Electroactive material
• 1000M cycles • 95-98% charge efficiency• -40 to 85 oC
• 1M cycles • 99% charge efficiency• -40 to 85 oC
• 10000 cycles • 85-99% charge efficiency• -10 to 60 oC
Batteries: State-of-the-Art • Lead Acid • Nickel–Cadmium• Lithium-ion
• Lithium cobalt oxide LiCoO2 (metal oxide)• Lithium manganese oxide LiMn2O4 (tunneled structure)• Lithium iron-phosphate LiFePO4 (olivine structure)
20
IOXUS super capacitor
21
Batteries
22
• Basic structure• Battery cell• Cell arrangements• Balancing circuits
• Modeling• Life and modeling
• Cycles• Current dependence • Temperature
dependence
• Positive electrode
• Negative electrode (carbon-graphite)
• Electrolyte and separator
Modeling
23
Life Model- Charge capacitace
24
Capacity loss as a function of charge and discharge bandwidth.
Nissan Leaf case https://www.nrel.gov/docs/fy13osti/58550.pdf
http://batteryuniversity.com/learn/article/bu_808b_what_causes_li_ion_to_die
Life model _Impedance Real Part and Aging
25
Battery dimensioning Charge and discharge
Solar –storage relation
27
Peak demand ( other aspect )
Battery Spec TemperatureCharge and Discharge
28
DC LINK
+
-
FilterInverter
Grid
~
Transformer
Battery
DC
DC
DC/DCConverter
Storage Power Conversion @
IN (1C)
Curr
ent p
.u
Temp (oC)
+
-~
DC
AC
DC/AC
-
IACVAC
IDCVDC
Chart1
DisCharge-20-15-10-50510152025303540455011111111111110.80.8Charge-20-15-10-5051015202530354045500.250.250.80.80.80.80.80.80.80.80.25
Sheet1
Units 5000/year (30 amps)USAEuro largeEuro
Power in KW7.26.93.63680
Price w/$$0.114$0.119$0.201
Inductor inverter$70$60
Inductor DCDC10070
Silicon Inverter6060
silicon DCDC6060
heatsink inverter3030
heatsink DC/DC3030
enclosure and fan150120
PC ( driver , voltage sensor)5050
PC microcontroller7070
ATS and connection5050
current sensors 3030
web connection4040
connectors4025
filters and high volatge protection4030
$820$725
Battery Specs TemperatureCharge and Discharge Energy storage
29
+
-~
DC
AC
DC/AC
IAC VACIDCVDC
IDC_ CHARGE = 0.8 P.UIDC_ DISCHARGE=1.0 P.U
+
-~
DC
AC IACVAC
IDCVDC
ACRMSRMSDCDCDC PVIVIP =⋅== .. ηη η
IDC_ DISCHARGEηIDC_ CHARGE = η >0.8
Energy and Power Arrangement
30
3 ampere-hours, 3.2 V 14x16
+
-~
DC
AC
DC/AC
IAC VACIDCVDC
Power= kW
η
Energy = kW/h
Battery system in a nanogrid go from 4kw/h to 16 kW/h
Inverters Fundamentals
Solar Inverter Evolution
* Kouro, S. Leon, J.I. ; Vinnikov, D. ; Franquelo, L.G. “Grid-Connected Photovoltaic Systems: An Overview of Recent Research and Emerging PV Converter Technology” Industrial Electronics Magazine, IEEE Volume:9 , Issue: 1 P:47 - 61 March 2015
LF- Transformer HF-Transformer Transformerless
Safety Parasitic current
32
Bi-directional Inverter ( Voltages based)
33
• Inverter Topology Type (Basic topologies and their advantages and disadvantages)
• Inverter Connection Type• Low-frequency transformer:
• The basic structure consists of one or more H-bridges Single H-bridge, high PWM • Center tap• Multiple H-bridges with interleaving
• The course contains some design examples.• High-frequency transformer
• The isolation is accomplished by high-frequency switching on the DC side using a high-frequency core, traditionally ferrite. Recent developments in low-cost and low-loss materials are challenging ferrite use.
• Topology and Design examples, including inverter and magnetic parts • Use of new semiconductors GaN and SIC
• TransformerlessEliminating the transformer reduces cost and significantly improves efficiency. This course analyzes the topologies that can achieve transformerless operation
Voltages Based Bi-directional inverter
Voltage Based Inverter
LF- Transformer (UPS)
HF-Transformer
Transformerless
Low Frequency Bi-directional inverter
Voltage Inverter
NAfBVRMS .44.4 max=
)()( tdt
Ntv ωΦ∂−=
Φ
Low Frequency Bi-directional inverterinterleaving
V
20kHz
HF Inverter _Hard Switch
High frequency ZCS
Vicor solution
Xiaoyan Yu and Paul Yeaman, “A new high efficiency isolated bidirectional DC-DC converter for DC-bus and battery bank interface
Transformerless Design _Motivation
• Cost reduction with additional weight and size reduction
• Efficiency increase and low cost
Average Parameter Comparisonsfor PV Inverters up to 6.5kW
Transformerless LF-Transformer
HF-Transformer
Avg. Efficiency (%) 95.7 94.5 94.1Avg. Power per Weight (kW/kg) 0.213 0.0753 0.168
Avg. Power per Volume (kW/m3) 115.2 84.7 80.2
EXAMPLE OF TRANSFORMERLESSINVERTER
GRID
500uH
20uf
V
+
_
V
+
_
DC-LinkBattery
11 12 13 14
DC-DC Split phase Inverter
BidirectionalControl 15
INVERTER DEVICE, ENERGY STORAGE SYSTEM AND METHOD OF CONTROLLING AN INVERTER DEVICEPublication number: 20170077836
https://patents.justia.com/patent/20170077836
With interleaving7KW 2- Split phase system 240/120V
2000uf
GRID
500uH
20uf
V
+
_
V
+
_
PRINCIPLE OF OPERATION 3-LEVEL
V2
V2
+
+
-
-
Positive Buck
SW
Negative Buck
on
PWM1
2
3
4
1
3
4
2
V2
+
-
V2
+
-
Positive Buck
Negative Buck
SW
NCP NCP2
Reverse energy transfer
on
PWM1
2
3
4~
+
-
Short circuit the inductor
VL
OFF
PWM1
2
3
4~
+
-
Regenerating Stage Charging the capacitor
VL
DC/DC basic operation
1
2
V
+
-
Discharge Charge
PWM1
2
V
+
-
PWMONOFF
OFF OFF
1
2
V
+
-
PWM
ON
OFF
1
2
V
+
-
PWMOFF
OFF
TRANSFORMERLESS OPERATION
DC LINK
+
-
Filter
Inverter
Grid
~
Transformer
Battery
DC
DC
DC/DCConverter
+
-
L
Para
sitic
cap
acita
nces
L
DC LINK
+
-
FilterInverter
Grid
~
Transformer
Battery DC/DC
Converter
LPa
rasi
tic
capa
cita
nces
(a)
(b)
dA
QVC
AdQdzEV o
o
d εε
==⇒== ∫.
0
A: total area of the plateD: distance between the platesεo: permittivity constant
8.8541× 10−12 F/m
Ground current for 1uF total parasitic capacitance
0
0.2
0.4
0.6
0.8
1
0 0.002 0.004 0.006 0.008 0.01 0.012
Tota
l Par
asitc
Cap
acia
tanc
e (u
F)
Distance beetween the plates d ( mm)
Total Parasitic Capacitance for 100 m2
C P=1uf , F DC= 10kHz F INV=16kHz
1A>0.47A
Evaluation Ground Current UL 1741
DC LINK
+
-
FilterInverter
Grid
~
Transformer
Battery DC/DC
Converter
L
Para
sitic
ca
paci
tanc
es
1mH
C P=10uf , F DC= 10kHz F INV=16kHz
1A
C P=1uf , F DC= 10kHz F INV=16kHz
1A>0.47A
Current Based Bi-directional inverter
DC AC DC AC DC AC
AC-link and bidirectional switches
SOFT SWITCHED HIGH FREQUENCY AC-LINK CONVERTER
ANAND KUMAR BALAKRISHNAN
Inverter tied-grid control
Generalized d,q control
Decoupling
Battery DC BUS Current Control PWM
Modulator Transformation
BAT + PI PI
Lω
Lω
Id
abc
dq
abc
dq
abc
dq
abcαβ
PI0
Grid
ACFilter
BAT
PLL
+ ++Error
+
Id
VDC
+
++++
+--
Inverter
+ +- ++ +
Iq
Vd
Vq
-
Iqref
+
POWER RELATION BETWEEN A BATTERY SYSTEMAND A SINGLE PHASE AC SYSTEM(
DC LINK
+
-
Filter
Inverter
Grid
~
Battery
DC
DC
DC/DCConverter
V DC
IDC(t)
I(t)AC
V(t)AC
200
100%
122%
(%)
(a)
(b)
Inverter Control
Power ACVrms ACIrms AC
I(t)AC Ref
V(t)AC
VDC(t)Battery
P(t)AC
VDC(t)Link
IDC(t)Battery
Power ACVrms ACIrms AC
I(t)AC Ref
VBattery
P(t)AC
VDCLink
Ibatt_ref
V(t)AC-
+
I(t)ACPIPWM
+
PI
PWMIBattery
-(b)(a)
Stand Alone
GUI
GUI and Weather Prediction
Energy Storage Prices • 10,000 cycles and/or 10 years, 80% charge
DC Battery PackAC System
http://eupd-research.com/59
Nanogrid-Energy Storage: Why Now?
Renewables Intermittence (generate “the need”)Price (large price reduction)Regulation (zero export to the grid)Tariffs (peak demand) Weather Prediction via Internet Power grid reliability and safety Smart Grid
Technology Conversion
To Availability and Affordability
60
Thanks! Questions?
61
Residential Battery Storage: �The cornerstone of the Nanogrid and distributed power systemsPower System Centralized vs. Distributed Distributed Paradigm Shift - RenewablesMinimum-cost of Electrification �Electrification Model (REM) �Nanogrid Operation Mode Power Quality Issues (Back up Mode) Residential Nanogrid �DC-AC Basic DC and AC Nanogrids: �Solar and Energy StorageDC Residential Nanogrid DC Residential Nanogrid- Control AC Residential NanogridLoad Handling and Criticality Droop AC control ( Inverter) Droop AC control Universal Droop Control of InvertersFundamentals�Back up battery storageEnergy Storage (Why Battery & Capacitor?)Time responses Fast Energy Storage Batteries: State-of-the-Art IOXUS super capacitor BatteriesModelingLife Model- Charge capacitace Life model _Impedance �Real Part and AgingBattery dimensioning �Charge and discharge Solar –storage relation Battery Spec Temperature�Charge and DischargeBattery Specs Temperature�Charge and Discharge Energy storageEnergy and Power Arrangement Inverters Fundamentals Solar Inverter EvolutionBi-directional Inverter ( Voltages based) Voltages Based Bi-directional inverter Low Frequency Bi-directional inverter Low Frequency Bi-directional inverter�interleavingHF Inverter _Hard Switch High frequency ZCSVicor solutionTransformerless Design _Motivation Average Parameter Comparisons� for PV Inverters up to 6.5kW�Example of Transformerless�Inverter With interleavingPrinciple of Operation 3-LevelReverse energy transfer �DC/DC basic operation Transformerless Operation Ground current for 1uF total parasitic capacitance Evaluation Ground Current UL 1741 Current Based Bi-directional inverter AC-link and bidirectional switchesInverter tied-grid controlGeneralized d,q controlPower relation between a battery system and a single phase AC system�Inverter ControlStand AloneGUIGUI and Weather Prediction Energy Storage Prices Nanogrid-Energy Storage: Why Now?Thanks! Questions?