RE08
Complete Inverter Design Training:
Focus on 3Ph vs. Central Inverters
Outline for today’s training
•Company Overview
•Commercial Design Considerations
•SolrenView web-based Monitoring
•Residential Solutions
•Utility-Scale & Medium Voltage PV Systems
•NEC 2014, Arc Fault & Rapid Shutdown
Company Overview
History – Products – Quality – Service
Solectria – A Yaskawa
Company
Overview – History - Highlights
Solectria History
Yaskawa Electric Acquires Solectria
Renewables as wholly owned subsidiary
ARCCOM (AFDI String Combiner)
Introduction
•
•
•
•
1989 – Solectria Corporation founded
2005 – Solectria Corp. EV division sold to
Azure Dynamics
2005 – Solectria Renewables founded
2014 – Solectria became wholly owned
subsidiary of Yaskawa Electric
Introduced the SGI 500XTM & SGI 750XTM
External Transformer
Introduced SGI 500 Premium Efficiency model with
97.5% CEC efficiency – highest in the industry
Disconnecting String Combiners
Introduced
PVI 14-28TL, 3-phase
transformerless inverters
New SolrenView GUI
Introduced
Solectria divests
vehicle products to
Azure Dynamics
Introduced PVI 50/60/75/85/100KW
& Premium Efficiency Models
PVI 13-15KW
UL Listed
Capacity Expansion to
200MW
SolrenView Web
Monitoring Introduced
Original 10kW
UL Listed
PVI 60/77/90KW
UL Listed
Solectria
Corporation
Founded
1989
60/82/95KW
UL Listed
Solectria
Renewables
Founded
Capacity
Expansion
to 350MW
SGI Series
UL Listed
SGI 500XT transformerless 600V
DC inverter introduced
PVI 3000-5300
Introduced
MSS
Introduced
2005
2006
PVI 3800-7600TL,
1Ph transformerless
inverters
2007
2008
2009
2010
2011
Capacity Expansion to
800MW
2012
2013
2014
Solectria - North American Support
Nationwide service locations to support
Commissioning
Rapid response times
Strategies in place for international expansion
Service
Solectria Sales
Solectria Office/Sales/Service
Solectria’s Steady Growth
2009 to present
Cumulative Sales (MW)
1,000
800
600
400
200
2009
2010
2011
2012
2013
2014e
2013/2014 Company Highlights
•
•
•
•
Introduction of three-phase string inverters
Introduction of ARCCOM arc fault detection and rapid shutdown
combiner boxes for 600VDC and 1000VDC central inverters
Introduction of SGI 500XTM and SGI 750XTM
Acquisition of Solectria Renewables by Yaskawa Electric Corp.
Solectria & Yaskawa
Yaskawa Electric Corp:
• $3.6 billion Japanese firm focused on motor drives, automation controls
and other electrical components
• Company founded in 1915
• 5th largest Japanese inverter supplier
• Global leader in quality
• Manufacturing locations in strategic PV markets
• Track record for technological advancement and leadership
Solectria & Yaskawa
So what does this mean for our customers?
 Immediately enhanced bankability
 Warranty backing by bigger company
 Solectria is 100% wholly owned subsidiary
 Same team in place as before (sales, marketing, customer
services, executives)
 Same manufacturing locations and product offerings
 Potential for new market entry in the future
 Access to world class quality systems
… Even More Solutions from the Industry’s
Best Inverter Lineup
PV Inverters
Utility
External Transformer Inverters
Megawatt Solar Stations
500-750 kW
1-2MW
Commercial
Central Inverters,
3-Phase String
50-100, 225-500 kW
14-28 kW
Residential
String Inverters
3.8-7.6 kW
String Combiners
Web-Based Monitoring
PVI 3800-7600TL
SGI 225-500PE
PVI 14-20TL
PVI 23-28TL
SGI 500XT
PVI 50-100KW
SGI 500XTM
SGI 750XTM
What Makes Solectria
Different
Performance
•
•
•
•
Products compliant with NEC 2014
Market leading CEC efficiencies
Proven 99%+ uptime performance
Over 10 years’ experience in the marketplace
Reliability
•
•
Founded on 20 years of electric vehicle manufacturing
Proven 99%+ uptime performance
•
Strategically located service technicians and third party
service providers
Serviceable design minimizes downtime and
maximizes energy harvest
Serviceability
•
•
Bankability
•
Backed by Yaskawa, a proven global leader in inverter
drive systems
7 consecutive years of profitability and financial health
Design Considerations
DC Considerations
AC Design Considerations
Solectria Commercial Solutions
String Sizing
Recommendations
String Sizing
RECOMMENDATION #1
Use Max Allowable String Size to…
•
Reduced BOS Costs - Fewer strings means fewer
combiner boxes and fewer PV source and output
circuits
•
Reduce System Losses - fewer circuits and higher
voltage/lower total current
•
Maximize Production for System Life
o
Ensures string Vmp stays within the MPPT range of
inverter for array life.
o
Protects from Vmp calc “shortcomings” and high
AC voltage
Of course, using max. number of modules is not always possible or preferred for other
reasons (complex layout, odd string size, carport…)
Next Stage in Design Evolution: 1000V Systems
String Sizing
RECOMMENDATION #2
Use ASHRAE Low Temperature
(a.k.a. Extreme Annual Mean Minimum Design Dry Bulb Temperature)
•
•
•
•
Often yields higher max string size
Supported by:
o
NEC 2011 690.7(A) Informational Note
o
“Array Voltage Considerations”, B.
Brooks, SolarPro Oct/Nov 2010
CHECK WITH INSPECTOR IN NEC 2008
OR 2005 LAND!!
SolarABC’s Map Tool
www.solarabcs.org/about/publications/reports/expedited-permit/map/
String Sizing – (example)
Use Solectria PV System Builder (www.solren.com)
• Location: Atlantic City, NJ
• Array Size: 600kW DC
• Module: Sharp NU-U235F1
• Inverter: PVI 500
Record Low/Average High
(Traditional Approach)
-23°C/29°C
 13 Modules Per String
 196 Strings
ASHRAE
-16°C/33°C
 14 Modules Per String
 182 Strings
THAT’S ONE LESS
14-STRING COMBINER AND HOME RUN
WIRING/CONDUIT!!
String Sizing
RECOMMENDATION #3
• Make sure that your string voltage is well above the min.
MPPT voltage of the inverter
Remember:
• Voltage Drop – The voltage at the inverter will be lower than the
string voltage due to voltage drop.
• Cell Temp – Is an Estimate
Based upon “Average High” or “ASHRAE”
Include estimated racking adder
• Different methods for calculating k_Vmp
• High Line Voltage – Increases the Min. MPPT voltage
String Mismatch (Voltage
Mismatch)
BEST PRACTICE:
Avoid combining different “Sting Types” to the same MPPT channel.
String Types
•
String Size
•
Tilt Angle
•
Azimuth Angle (Orientation)
•
Different module types
•
New and Old of the same module
•
Shaded and Unshaded Strings
Combining dissimilar strings results in String “Mismatch Losses”
(Each string type has a specific MPP voltage, but when
combined in parallel all strings are forced to operate at the same
voltage...)
String Mismatch (Voltage Mismatch)
×
6.084kW when
on same MPPT channel
= 1.2% Mismatch Loss
12 Module Strings:
3.12kW @MPP
11 Module Strings:
2.94kW @MPP
××
6.15kW
Oversizing
Oversizing
What is the Array-to-Inverter Ratio?
• The ratio of Array’s STC Nameplate Power to Inverter’s Rated Power
• Also called: DC/AC Ratio, Oversizing Ratio, Overloading Ratio
Example:
Array: 120kW
Inverter: PVI 100KW
120kW = 1.2
100kW
…the Array-to-Inverter
Ratio is 1.2 (120%)
120kW PV Array
PVI 100KW
Oversizing
Historically:
•
•
Due to high module prices, optimal oversizing: 1.10 to 1.25
Design Goal:
o
o
o
Optimize Annual Energy Harvest per Panel = Optimize Specific Yield (Annual
kWh/kWdc)
Little to No clipping
Minimal shading
Today:
•Cheaper Module Prices
Larger array feeding a fixed size inverter results in greater production
Greater production across the same fixed AC costs
•Time-of-Use Utility Rates
Generate most energy when it has the most value
Designers are exploring vary tilt angle and power density and encroaching into shaded regions
Daily Output Profile: Clipping Day
• Oversized systems produce more energy
• Oversized systems match TOU rate structures
Daily Output Profile: Non-Clipping
Day
How to determine “Optimal” Array
to Inverter Ratio
Perform Oversizing Analysis
using simulation program
(PVsyst, PV*SOL, SAM) =>
Feeds Financial Model
Higher or Lower A-I Ratio?
The further away your system is from “Optimal” the Higher the “Best” Array-to-Inverter Ratio
HIGHER Array-to-Inverter Ratios:
•
•
•
•
•
•
•
•
Large Commercial/Utility Scale Projects
TOU Rate Structure
Cheaper Modules
Low/No Tilt Angle
High Soiling/Don’t want to clean
Off-optimal orientation
Shading (inter-row, obstructions)
Fixed ACkW interconnection
LOWER Array-to-Inverter Ratios:
•
•
•
•
High Altitude
Constant “Cooler” temps year round
Residential Systems, Light Commercial Systems
Clipping???!!! Customers
Oversizing Reverences
SolarPower World: “Supersize It,” J. Fiorelli, M. Zuercher, June 2013
SolarPro Magazine: “Designing for Value in Large-Scale PV Systems,” G.
Everts and M. LeDucq, June/July 2013
SolarPro Magazine: “Optimal PV-to-Inverter Sizing Ratio,” A. Gregg, C.
Adcock, B. Brooks, April/May 2010
Voltage Drop
Voltage Drop
DC and AC conductors are sized to meet:
• Code Requirements (NEC) …..Safety
• Voltage Drop Requirements ….. Performance/Efficiency
Best Practices for Voltage Drop
•
•
DC Voltage Drop – Limit to 1-1.5%*
AC Voltage Drop – Limit to 0.5 to 1%*
Voltage drop specs are often called out in RFP Spec.
*See next slide
Voltage Drop
*Of course, there are always exceptions….
Inverters
Why Limit Voltage Drop?
Reduce Resistive
Losses
Voltage Drop % is a Power Loss Fraction.
Vdrop
I
+
+
Vnom
-
-
1% Voltage Drop
means DC circuits
are 99% Efficient
(at max power…
more efficient at
lower power)
Why Limit Voltage Drop?
Minimize Voltage Rise
The inverter sees the grid voltage plus the AC Voltage Drop. If grid
voltage is high and voltage drop is high >>> Nuisance Tripping
Trip
+10%
Vrise
Vnom
-12%
Voltage at
Inverter output
terminals
Voltage along
AC output
cables
Voltage at
Point-ofInterconnection
DC Design –
Overcurrent Protection
DC Overcurrent Protection
DC OCPD…Fancy Name for:
Fuse
LOCATION:
FUNCTION:
Circuit Breaker
Combiner Boxes
and Subcombiner Boxes
Subcombiner
= Recombiner
Combiner Box
= String Combiner Box
= Array Combiner Box
DC Overcurrent Protection
DC OCPD…Fancy Name for:
Fuse
Circuit Breaker
LOCATION Combiner Boxes and Subcombiner Boxes
:FUNCTION: Protects cables
FAULT!
Subcombiner
= Recombiner
Combiner Box
= String Combiner Box
= Array Combiner Box
DC Overcurrent Protection
[NEC 690.8]
Number
of String
Feeding the
OCPD
Example Calcs:
1.25 for OCPD
Derating
Module
Short Circuit
Current
1.25
Factor for
Increased
Irradiance
Isc = 8.46
What is the min. size string fuse?
1 x 8.46 x 1.56 = 13.2A …………………..=> 15A
What is min. size fuse for 12 string combiner box?
12 x 8.46 x 1.56 = 158.4………….……..=> 175A
Select
next standard
fuse size up
in NEC 240.6
PVI 50-100KW Subcombiner Options
Ground
Bars
DC
Surge
arrestor
PV
Negative
Ground
Bars
PV Positives, breaker option
(2 positions, 300A fuses)
DC DISCONNECT
With SUBCOMBINER
SolZone
Sensors
PV Positives, fuse option
(6 positions, 100A fuses)
SGI DC Disconnect Connection
Current Transducers
(CT’s)
Positions
Fuse Range
Fuse Range
8 Breaker Option
(7, 400A; 1, 350A)
16 Fuse Option
(4, 150A; 4, 125A; 8, 175A)
AC Design
Commercial Service
Types
Commercial Service Types:
COMMON
3-Phase, Four-Wire Grounded Wye
Voltage
Phase-to-Phase
Phase-to-Neutral
208
120
480
277
Commercial Service Types:
COMMON
3-Phase, Three-Wire Unrounded Delta
Voltage
Phase-to-Phase
Phase-to-Neutral
208
---
240
---
480
---
Commercial Service Types:
UNCOMMON
High-Leg Delta (Red Leg, Wild Leg, Bastard Led Delta, Crazy
Leg)
Voltage
Phase-to-Phase
Phase-to-Neutral
240
120 (A-to-N)
120 (C-to-N)
208 (B-to-N)
Commercial Service Types:
UNCOMMON
Corner Grounded Delta
Voltage
Phase-to-Phase
Phase-to-Neutral
240
---
480
---
Commercial Service Types:
UNCOMMON
Open Delta
Voltage
Phase-to-Phase
Phase-to-Neutral
240
---
480
---
Commercial Service Types:
SERVICE TYPE
Grounded Wye
NOTES
SUPPORTED?
Most common type of 480V,
208V service
Y
Ungrounded
Delta
Common for 480V, 240V, 208V
motor control centers
Y
High-Leg Delta
240V service sometimes found
in agricultural and older urban
areas
Y
Corner Grounded Uncommon
Delta
Open Delta
Uncommon
N
N
Commercial Service Types:
How to confirm the electrical service type?
•Transformer/Transformer Nameplate
•Call Utility
•Have qualified person measure all voltages line-to-line and line-to-ground
…Also confirm kVA rating of utility transformer…
Is a Neutral Required?
Solectria inverters output balance three-phase current, as a result a neutral is not
required for inverter operation
If required by a utility (for effective grounding or establishing ground reference),
Solectria PVI 50-100 and SGI 225-500 are available with 4-Wire Option, where
neutral connection point is solidly connected to the isolation transformer neutral
point.
When connecting the inverter as a 4-wire device currents may flow on neutral due to
voltage imbalance and harmonics on the distribution line feeding the site.
Size Neutral conductor cable equal to line conductors.
Example Inverter Block Diagram (from PVI 50-100KW Manual)
What About on TL Inverters???
3 Phase Solectria TLs often require a neutral reference.
The PVI -20 TL is the only inverter in the 3 phase TL family that
can work with a 480V Delta or WYE
The PVI-14, 23, 28 TL inverters do require a neutral reference.
The neutral IS NOT a current carrying conductor! > Can be sized
differently than other conductors.
Bonding Jumper between ground and the neutral terminal has
been tested and CAN work but not recommended.
Likelihood that installers will double up wire in terminals
Has been know to not always provide the appropriate neutral
reference.
Solectria Recommendation: Plan on a neutral conductor for
sensing
AC Design Interconnections
Interconnections
One of the factors that can limit the size of a
project….
Limiting Factors (Design Constraints)
•Interconnection
Existing Electrical Infrastructure (Service Rating, Utility Transformer,
Interconnection Panel…)
Utility
•Space/Area
•Budget
•Utility
Interconnection Types
Where to interconnect?
Supply Side
Interconnection
Grid
Utility Meter
Service
Disconnecting
Means
Load Side
Interconnection
To Loads
To Subpanel
Main Service
Panel
Rules of Interconnections
•NEC 2011 and 2014 – Found in 705.12
•NEC 2008 – Found in 690.64
Them’s the rules!
Supply Side Connections
• “Line Side Connection” = “Line Side Tap”
•Between Utility Meter and Service Disconnecting Means
Supply Side
•Connection made via:
Connections
3
1. Splicing Utility Feeder Conductors
2. Tapping bus bars on line side of service disconnecting means
3. Double Lugging on load side of utility meter or on line side of service
disconnect
4. Junction Box between meter and service disconnecting means and
installing junction box with terminal block
Check with manufacturer to find out what is allowed per UL listing…
Work with the utility b/c you’ll have to disconnect power…
1
4
2
3
Supply Side Connections
1. Splicing Utility Feeder Conductors
Insulation Piercing
Tap Connector
Supply Side Connections
2. Tapping bus bars on line side of service
disconnecting means
Supply Side Connections
3. Junction Box between meter and service
disconnecting means and installing junction box with
terminal block
Polaris
Insulating Terminal Block
Gutter/Parallel Tap
Connector
Supply Side Connections (Cont.)
Must also follow rules of NEC 230 “Services”
•Service disconnecting means shall have of at least 60A rating (230.79(D)) (Smaller fuses
can be used)
•Six Switch Rule (230.71)?
•Overcurrent protection must be integrated or adjacent to the disconnecting means (230.91)
•Min conductor size of #8 Cu and #6 Al between point of connection and disconnect
(230.23(B), 230.31(B)) (60A disco will require #2 terminals anyways)
OTHER RULES
•kAIC of overcurrent protection devices must exceed available fault current from the service
(110.9 and 110.10)
•LIMITING FACTOR: Sum of overcurrent protection devices from power producing sources
can’t exceed the rating of the service (705.12(A))
•CHECK WITH YOUR UTILITY for additional requirements (ex. Lockable disconnect,
Location… Labeling)
Load Side Connections
•NEC 705.12(D)
Load Side
•Typically backfeeding a breaker
Connections
Breaker must be suitable for backfeeding
•Connection can be made in any distribution
equipment (subpanel)
•Dedicated circuit breaker/fused disconnect
To
•120% Rule – Breakers from sources feeding a
Loads
panel can exceed panel rating by 120%
Panel must be labeled that it is supplied by
multiple sources
Can downsize the main breaker in some cases
To
120% Does not apply to combining panel
Subpanel
When 120% rule limits system size (supply
side connection)
Main Service
•Ground fault breaker must be suitable for
Panel
backfeed
Understanding Interconnections
What does this tell us?
Grid
•Overcurrent at POI protects the inverter output circuit
conductors.
•Each inverter output circuit requires overcurrent (Dedicated
Circuit Rule of NEC)
•Integrated AC breaker or fusing does not protect inverter output
Inverter
cables
Output
Circuit
To Loads
Array
Inverter
FAULT!
Main Service
Panel
Other Design Topics
Ungrounded
Systems
Ungrounded Systems
Also called “Floating Systems,” but not this
type!!!
Far Niente Winery, Oakville, CA, Napa Valley, ~400kW across land and lake
3-P String vs. Central Inverters
There are many considerations…
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
DC Wiring
DC Wiring Type
Combiner Boxes
AC Combining Panel
AC Collection System
Mounting (wall vs. pad)
Communications Wiring
Monitoring Granularity
Ground Fault
Arc Fault
PID
Full Power Temp
Wire Coloring
Wiring Isolation?
Central Point of Utility Control
Weight
Shipping Cost
Efficiency
Oversizability
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
MPPT Range
String Balancing
NEMA Rating
Design Flexibility
Failure Points/Part Count
Noise
Permitting
AC Voltage
1000Vdc Module?
DC Disconnects
Revenue Grade Metering
Utility Acceptance
Protective Relaying
Remote Shutdown
Mismatch Losses
MPPT Range
Commissioning
Service
O&M
PVI 14TL, 20TL
PVI 50-100KW
Topics Covered


Examine $/W vs. kW for String and Central
Architectures
Architecture Considerations
 Performance
 Monitoring
 Design
 Other (Code, Safety, PID, EG)
Project Specific Variability








Inverter Pad/Mounting Costs
Monitoring/Metering Level
Home runs length (Roof-to-ground length)
Arc-fault
Ground Fault
Rapid Shutdown
Effective Grounding
PID
Why 480Vac?






DC circuits are sized to:
1.25 x 1.25 x Short Circuit Current =
1.25 x 1.25 x 1.1 x DC Rated Current =
1.72 x “Rated Current”
AC circuits are sized to:
1.25 x Rated Current
3-phase system is better use of conductor than a 1-phase
system even at 1000V
DC Combining gear is more expensive than AC combining
gear
Run favors AC even considering ground conductor and
communications cable/conduit.
Exception: Very long run (due to need to upsize for
voltage drop)
AC run has:
• Less Cable Volume
• Smaller conduits
Why 480Vac - Example
Performance
3ɸ-String Inverters
 Efficiency 0% to 1% CEC Efficiency Gain
 *Minor Benefit* Lower Mismatch Losses
 *Minor Benefit* Lower Start Voltage
 Array may be susceptible to PID
 Downtime: More failures/shorter duration/duration of
downtime may vary (higher percentage of the array that
down, the short the downtime)
Central Inverters
 Array not susceptible to PID
 Downtime: Less failures/shorter duration/greater
percentage of the system down
Design Considerations
3ɸ-String Inverters
 String Sizing/Layout Flexibility Tied to More/Smaller MPPT Zones
 Standardize designs with a certain product
Central Inverters
 Greater sub-array size flexibility tied to subcombiner fuse size
increments
 Oversizing flexibility allows optimization array-to-inverter ratio
 Granular inverter increments with Solectria PVI/SGI
Design Considerations

3ɸ-String Inverters have an 8 string input

Racking designed around 8 strings per row allows for
scalable “cookie cutter” designs
Design Considerations
30MW: Qty. 504- PVI 82kW Inverters

Depending on system
size, a distributed
approach can still be
achieved with “Central”
inverters.

Redundancy is based on
number of inverters, not
inverter kW rating.
Design Considerations

1.1MW: PVI 95kW Inverters
3ɸ-String Inverters
installed in carports
made inaccessible
require additional
planning for service
New/Imminent Code
Requirements
NEC 2011
Arc Fault on Roof Tops (690.11)
Fuse Servicing Disconnects
(690.16)
NEC 2014
Arc Fault Everywhere (690.11)
Grounded Conductor Ground
Fault (690.5)
Rapid Shutdown (690.12)
NEC 2014 Adoption
Currently 22 States following NEC 2014
Ground Fault Detection

3ɸ-string inverters have residual ground fault detection.
 Shorter DC runs decreases likelihood of ground fault.

2014 NEC requires grounded conductor (Blind-spot) ground fault
detection.

During ground fault only 3ɸ inverter
is taken offline rather than the
entire array.
 Better system uptime
 More focused troubleshooting
Figure from “Ungrounded PV Power Systems in the NEC,”
SolarPro, Aug./Sept. 2012
Potential Induced Degradation (PID)
3ɸ-String Inverters – Ungrounded Arrays/Bipolar
 Ungrounded arrays may be susceptible to PID.
 PID “offset” box can be used to reverse the effects of PID
Central Inverters – Grounded Arrays
 Grounded Arrays do not experience PID.
+
Glass
N-Type
P-Type
+
-
+
+
-
+
Frame
Inverter Topology
DC Input and Filtering
*DC +/- Fusing Not Shown
Boost
Stage
Inverter
Circuit
AC Filtering and Output
Effective Grounding
3ɸ-String Inverters
 Require grounding transformer for effective grounding
Central Inverters
 Can be effectively grounded via 4-wire solid ground (neutral kit),
4-wire impedance ground (grounding reactor), 3-wire with
grounding transformer
Smart Inverter Functions
…PF adjustment, Ramp Rate, Curtailment, Volt-VAR
3ɸ-String Inverters
 Have smart inverter functions
 Multiple points of communication and control
Central Inverters
 Have advanced smart inverter functions
 Single point of communication and control
Service and Warranty
3ɸ-String Inverters




Service Frequency: More points of failures
=> More visits (may not be more frequent)
Smaller percentage of system effected
Duration of Downtime: Shorter
Service: “Rip and Replace,” Replacing on
roof may be a challenge.
Service and Warranty
Central Inverters





Service Frequency: Fewer points of failure => Fewer visits
Larger percentage of system effected
Duration of Downtime: Longer
Service: Manufacturer Trained Rep
Warranty: 5 year
What Architecture is Best?


The “best” architecture is the one that optimizes the financial
performance of the project.
Financial performance is determined by:
 Engineering Cost
 Installation Cost (Equipment and Labor)
 Performance/Uptime
Answer: It depends. Best
architecture will be project
specific.
Advanced
Inverter Features
Remote Shutdown
Why remotely shut down the inverter?
•Utility control
•Disabling inverter during back-up generator operation
•Integrating with Relaying
o
o
AC Relaying - Protective Relaying
DC Relaying - Residual ground fault detection systems
•Integration with BMS/Sprinkler System
Remote Shutdown
•PVI 50-100 and SGI 225-500 inverters come standard
with a 24V isolated Digital Input terminals to shut down
the inverter
•How is works:
Apply 24V to terminals → Inverter shuts down
Remove 24V from terminals → Inverter waits for 5min of stable grid, then
resumes conversion
•Shutdown rate is adjustable - 4 sec (default), As fast
as 0.16s
•Other options for remote shutdown
Modbus RTU/RS-485
Shunt Trip (not available in all models)
Remote Shutdown
24V Remote
Shutdown
Terminals
ve Comparison
Advantages/Benefit
s of using our
1000VDC inverters
Overview
Utility-Scale, External Transformer, 750 kW and 500 kW Inverters
•
•
•
•
•
•
External Transformer Inverter
98.2% Peak Efficiency
98.0% CEC Efficiency
Built-in redundancy
Fully-integrated design
RS485/MODBUS
communications
Options for utilities
–
–
–
–
–
Real power curtailment
Reactive power control
Voltage ride through
Frequency ride through
DMS Tie-in
Design Advantages/Benefits
•
Offers greatest amount of array isolation when the inverter is off
Standard DC disconnect & contactors – no external disconnect required
Less wiring = more cost savings
SMA – no disconnect option offered, only DC contactor
ABB/Sungrow – optional, external only
•
Only company to offer DC breaker option
Subcombiners – fuses or breakers – 4-16 positions
Utilizing breakers instead of fuses saves customers $10-15K
No need for external disconnect within 50 ft. (with fuses, this is required)
Most fused positions offered (SMA/ABB/Sungrow – 6-10 offered)
•
Only company to offer option for internal or external AC breaker
Others offer external option only (750kW)
Provides overcurrent protection
Only company to offer AC breaker with shunt trip
Allows the owner or utility to remotely disconnect the inverter from the grid
General Advantages/Benefits
•
Can operate in extremely cold/hot weather
Best operating temperature range: -40⁰F to +122⁰F
•
Lowest shading set back standards
Power Stage
Shortest height
Power stage contains all sensible/power/control electronics
Easily swapped in the field – minimizes downtime
More fault tolerance
Stainless steel enclosure option
Threaded inserts & knock outs on sides of unit allows for
attached mounting of communications, electronics, weather,
security etc.
Easy connections – saves time and $$
Greatest skid design options for both the 500/750
XTM Transformer Selection
External Transformer
Selection
Most often use “External Transformer” Inverters…
Higher Efficiencies/Less Losses
Used in both Stations and Stand-alone
SGI 500kW 480V System
MV XFMR
ISO.
XFMR
208V
480V
13.2kV
Two Transformers
1. Isolation XFMR
2. MV XFMR
SGI 500kW 480V
208V (“Native Output Voltage”)
SGI 500XTM 208V System
MV/ISO
XFMR
380V
13.2kV
One Transformer
1. MV/ISO XFMR
SGI 500XTM 380V
IMPORTANT - Follow inverter manufacturer’s transformer spec.
External Transformer Selection
Most often use “External Transformer” Inverters…
 Higher Efficiencies/Less Losses
 Used in both Stations and Stand-alone
SGI 500XTM 380V System
MV/ISO
XFMR
13.2kV
380V
One Transformer
1. MV/ISO XFMR
SGI 500XTM 380V
IMPORTANT - Follow inverter manufacturer’s transformer spec.
External Transformer
Selection
Most often use “External Transformer” Inverters…
 Higher Efficiencies/Less Losses
 Used in both Stations and Stand-alone
SGI 500XTM 380V System
MV/ISO
XFMR
13.2kV
380V
One Transformer
1. MV/ISO XFMR
SGI 500XTM 380V
IMPORTANT - Follow inverter manufacturer’s transformer spec.
External Transformer
Selection
See Isolation Transformer Specification
for Minimum Requirements
3 Windings
Low-High-Low
Minimum Impedances
Vector Groups
Electrostatic Shielding
External Transformer
Selection
See Isolation Transformer Specification
for Minimum Requirements
Fe
Low #1
High
Low #2
External Mounting
Provisions
External Equipment Mounting
•
8 Threaded inserts
o ¼-20 threads,
o .310” thread depth
•
Mount Uni-Strut
o for Communications
Enclosures
o Security
o Weather station
Ground Fault Detection
Ground Fault Detection

Bakersfield Target Fire

Blind spots in GFDI

XTM has DC contactors
 Segments the array

Residual Current Sensor
 500mA vs 5A
Figure from “The Ground Fault Protection Blind Spot”
Bill Brooks, January 2012
Ground Fault
Detection

PVI 3ɸ-string inverters have residual ground fault detection.
 Shorter DC runs decreases likelihood of ground fault.

2014 NEC requires grounded conductor (Blind-spot) ground fault
detection.
Figure from “Ungrounded PV Power Systems in the NEC,”
SolarPro, Aug./Sept. 2012
Overview
Communications
SolrenView web-based monitoring uses MODBUS
and RS-485/RS232 to communicate through
SCADA
SCADA is a computer system used to gather and
analyze data in real time
MODBUS is the communication protocol
RS-485/RS232 are the physical serial
layer/interface
MODBUS =
Way of communication
(ie. English language)
RS interface =
Paper (ie. physical medium)
SolrenView Home Page
Web-Based Monitoring
OVERVIEW - Web-based monitoring
Inverter Direct
Revenue Grade
Performance Charting
Real-time status notifications
Detailed system data
Reliable, safe, secure data storage
Options
Sub-Array Monitoring (SolZone)
Weather Station
Flash View
Agency Reporting
Hardware
Standard LCD Display
SolrenView Hardware is Fully Integrated for 3-Phase products
LCD Display provides:
o
o
o
o
o
kW, kWh, AC & DC Voltages,
AC Current, other data
Check and adjust settings
Direct interaction with
SolrenView and web-based
monitoring
Simple, user-friendly control
(no knocking)
Standard on all inverters,
50-95 kW
Hardware for Residential
Inverters (Inverter Direct)
SolrenView Hardware is not fully-integrated, but simple to install and set-up
Hardware for Residential
Inverters (Revenue Grade)
Hardware for Commercial
Inverters (Inverter Direct)
Factory Installed
Integrated SolrenView
Inverter-Direct Data Logging
Internet
Router
CAT 5 Cables
Each inverter connects individually to the internet router via the integrated
(factory installed) SolrenView
• “Plug-n-play” hook up
• Gateway connects to any number of inverters
• 3, 5, 10 years of internet support
Web-based Monitoring
STANDARD FEATURES
Inverter Monitoring
Login
Login
Site Overview Page
Various pages you
may cycle through
• Site overview
• Environmental
Footprint
• Project Details
• Analytics
• Detailed
Analytics
Photo of Project
AC Power Now
Weather information
(if no weather station,
weather data is pulled
from weather.com)
Lifetime Energy
Production
(MWh)
Energy Production Graph
Site Overview Page
Site name and Site Owner
Shows if system is online or offline
Date & current time
•
•
Amount of time
before next data
refresh
•
Feedback
Animated View
(Kiosk View now
available to all
customers)
Switch to “old
view”
Environmental Footprint
Page
Lifetime Energy Generated
Savings shown:
• CO2 tons of emissions avoided
• Gallons of gas offset
• Electric cars charged
• Days of powering 1 search engine data center
• Offsets pilgrim nuclear power plant for # of hours
• Offsets keystone coal power plant for # of hours
*NOTE: Calculations are based on straight multipliers
Shows various savings
Moves automatically,
but user can move
back and forth
manually as well
Project Details
Your photos of the
site; can add up to 6
If you order the kiosk
view option, this
scrolls automatically
If not, it is a manual
scroll
Shows:
• System size
• Location
• Inverters and amount of
inverters
• Can have text which would
be located below
Inverter Direct
Select 1 or 2 devices
you’d like to
compare:
•Inverter(s)
•Indirect information
(AC Energy, AC
Power, AC Current,
AC Voltage)
•Revenue grade
meter(s)
•Weather station(s)
•You may only select
rev. grade meters or
weather stations (&
their options) if you
have purchased
these options
Select any
2 items to
compare;
this allows
you to view
inverter
direct and
revenue
grade data
(if revenue
grade
and/or
weather
station has
not been
purchased,
these
options will
not show)
Inverter Direct
Move forward or
backward
dependent on
time settings
Select various time
periods OR a range to
view default is today
Download CSV data
for further analysis
Select various time
periods OR a range to
view default is today
Additional Features of Inverter
Direct Monitoring: Notifications
Automatic Email Notifications Based on Sensitivity Preference
AC power failures
AC voltage and frequency fluctuations
Ground faults in array
Inverter faults
Preventative alarms (fan life impending)
Underperformance (with SolZone)
Example Notification:
System Offline
System Name
Level of Severity
Error Message with
Time Stamp
Link to SolrenView
Live Site
Example Notification:
Check SolrenView Live Site
Status may be
listed as online or
offline
If system is “offline,”
resolution:
Either the internet is
unavailable, or the
SolrenView has lost power
Web-based Monitoring
OPTIONAL SERVICES
SolZone: Sub-Array Monitoring
Array
String combiners
Integrated
SolrenView
Integrated
Subcombiner
with Current
Transducers
PVI 60/82/95KW
SolZone – wired example
Current
Transducers
(CT’s)
Fuses
PVI95KW
95KW
PVI
Inside the DC Disconnect
SGI 225/250/266/300/500
SolZone – wired example
Inside (left side)
CT’s & Fuses
SGI 500
Fuses
Current
Transducers
(CT’s)
SolZone Site Example
Compare various zones & inverters
SolrenView Weather Station
Type 4 sealed enclosure
Weather Station Site Example
Weather station data; if weather station is not chosen as an option, the
weather icon and temperature outside will still show
SolrenView AIR cellular option
Cellular option (ethernet is standard) for PVI 60/82/95KW and
SGI Series
Great for remote sites – especially utilities
Low power consumption
Certified for hazardous environments
IPsec VPN to protect your data from unauthorized access
Standard SolrenView data package included
5 year standard warranty
Single-Phase, Transformerless Residential
Solutions
PVI 3800-7600TL
Transformerless string inverters
600 VDC
Highest industry peak and CEC efficiencies
Lightweight, compact design - smallest in the
industry
Quick and easy installation
Wide operating voltage range
DC disconnect
Options
Web-based monitoring
Revenue grade monitoring
DC arc-fault detection and interrupt (available
May/June 2014)
Equipment Overview
Wiring Box Info
Utility AC Voltage
Grid tied
60 Hz
Available for 208 or 240 Vac
These inverters should never
be connected to a 120 Vac
utility service
NEC 690.64(b)(1)
requires that the
inverter be
connected to a
dedicated circuit
with no other
outlets or devices
connected to the
same circuit
Utility AC Voltage
AC Voltage loss with different
size wires and lengths
Monitoring
RS-485 communication interface
Can address up to 31 daisy chained inverters
External SolrenView
Rapid Shutdown
Option
Rapid Shutdown Combiner Option
Solution to NEC 2014,
Article 690.12 (1Ph systems
must be able to shutdown
immediately at the source)
Integrates seamlessly with
Solectria’s PVI 38007600TL
1 Rapid Shutdown Box per
inverter (NOT per MPPT –
our RSD solution is built for
1 or 2 MPPTs)
Up to 4 string inputs
Specifications
12.4 x 10 x 2.2 in. (316 x 255 x 55.5 mm)*
*Dimensions do not include DC input wiring shown in photos; input wiring is included when RSD is
ordered
RSD Box for up to 2 MPPT, 4
strings
Mounting Rail
(included in
dimensions)
RSD Dimensions & Alternate Views
12.4 x 10 x 2.2 in. (316 x 255 x 55.5 mm)*
*Dimensions do not include DC input wiring shown in photos; input wiring is included when RSD is ordered
Mechanical Layout
Solectria Solution for 1Ph
Installations to Meet NEC 2014
Requirement
Method – 1 story, no additional
electronics
Method – 2 story, no additional
electronics
Method – 2 story, rapid shutdown
combiner
Method – 2 story, micro inverters
Medium Voltage Systems
Medium Voltage Vocabulary















Loop Feed
Radial Feed
kVA
Switch Gear
Potential Transformer (PT)
AC Collection System
Bushings
Elbow Arrestors
Protective Relays
Primary Metering
Riser Pole
Native Output Voltage
Current Limiting Fuse
ANSI Device Numbers
Shunt Trip






SCADA
RTU
DNP3
Tap Changer
Hot Stick
Expulsion/Bayonet Fuse
Medium Voltage Vocabulary
Medium Voltage Applications
Most Common Application:
Utility Scale Projects
Other Common Applications:
Primary Metering - Sites that are
primary metered (many large
commercial and industrial customers are
metered at medium voltage)
Long Runs - Sites with long runs from
inverter to the point of interconnection
Two Approaches for Inverters:
Medium Voltage Stations
Field integration of Inverter(s) with
External Transformer
Solectria Megawatt Solar Station
SGI 500XT Inverter(s) and MV XFMR
field integrated
Solectria SGI 500XT
Utility-Scale, External Transformer, 500 kW Inverters
External Transformer Inverter
98.4% Peak Efficiency
98.0% CEC Efficiency
Built-in redundancy
Fully-integrated design
RS485/MODBUS
communications
Options for utilities
Real power curtailment
Reactive power control
Voltage ride through
Frequency ride through
DMS Tie-in
Megawatt Solar Station:
225 kW - 2 MW
•
Direct connection
o
•
Multiple step sizes
o
•
Solar array to medium voltage utility power
1 MW-2 MW
Integrated Unit
o
Inverter, transformer, and medium voltage
switchgear
•
•
Provides quick and easy installation
May use any SMARTGRID series inverter:
• SGI 225-500
• SGI 500PE
• SGI 500XT
•
Options for utilities
Real power curtailment
Reactive power control
Voltage ride through
Frequency ride through
MSS shipping
MSS shipping
MSS 1MW or MSS 1MW-XT:
30,000-40,000 lbs (depends on options)
MSS 1.5MW: 50,000-55,000 lbs (depends on options)
MSS 2MW:
60,000-62,000 lbs (depends on options)
MSS Installation
Station vs. Stand Alone
What is best?... It’s the Project Team’s Preference!
PRE-ENGINEERED
STATIONS
- Pre-Engineered: Saves
engineering and procurement time for transformers, auxiliary
equipment, and cabling
- Pre-Engineered: Ensure
inverter/xfmr compatibility
- Factory Integrated
- Factory Tested
FIELD INTEGRATED
STATIONS
Lead time
Explore pricing from existing
or multiple vendors for
transformer, auxiliary
equipment, and integration
Work directly with
transformer, auxiliary
equipment vendors
... It’s the Project Team’s Preference!
Inverters in MV Systems
Most often use “External Transformer” Inverters…
Higher Efficiencies/Less Losses
Used in both Stations and Stand-alone
SGI 500kW 480V System
MV XFMR
ISO.
XFMR
208V
480V
13.2kV
Two Transformers
1. Isolation XFMR
2. MV XFMR
SGI 500kW 480V
208V (“Native Output Voltage”)
SGI 500XT 208V System
MV/ISO
XFMR
208V
13.2kV
One Transformer
1. MV/ISO XFMR
SGI 500XT 208V
IMPORTANT - Follow inverter manufacturer’s transformer spec.
External Xfmr Inverters in MV
Systems
Most often use “External Transformer” Inverters…
 Higher Efficiencies/Less Losses
 Used in both Stations and Stand-alone
SGI 750XTM 380V System
MV/ISO
XFMR
13.2kV
380V
One Transformer
1. MV/ISO XFMR
IMPORTANT - Follow inverter manufacturer’s transformer spec.
External Inverters in
MV Systems
Most often use “External Transformer” Inverters…
 Higher Efficiencies/Less Losses
 Used in both Stations and Stand-alone
SGI 750XTM 380V System
MV/ISO
XFMR
13.2kV
380V
One Transformer
1. MV/ISO XFMR
IMPORTANT - Follow inverter manufacturer’s transformer spec.
Inverters in MV
Systems
See Isolation Transformer Specification
for Minimum Requirements
3 Windings
Low-High-Low
Minimum Impedances
Vector Groups
Electrostatic Shielding
Inverters in MV
Systems
See Isolation Transformer Specification
for Minimum Requirements
Fe
Low
#1
High
Low
#2
MV Design: AC
Collection System
“Everything from the Inverter’s Output to the POI”
To Point-of-Interconnection
 MV Cable
 MV Transformer
 Switchgear
AC Collection System
 OCPD
 Disconnect Switches
 Protective Relaying
 PT’s/CT’s
 Revenue Metering
 Surge Arrestors
Inverters
Medium Voltage
Transformers
Loop vs. Radial Feed
Radial Feed
Loop Feed
Medium Voltage Transformers
Other Medium Voltage
Transformer Topics
kVA rating
High Voltage Winding
Low Voltage Winding
Efficiency/DOE Efficiency
Cooling/Dielectric Fluid
Fusing/Disconnect Switches
Tap Changers
Elbow Arrestors
Switch Gear
“Medium Voltage AC Combining Panel”
LOCATION OF:
… Feeder OCPD
… Protective
Relay?
… Revenue Meter?
Made by companies like Eaton, GE, Siemens, …
(Digital) Protective Relays
“Microprocessor based devices that that control PV plant in
response to voltage and current measurement”
USED WITH:
… Interconnection Breaker
… Instrument Transformers
Potential Transformers (PTs) … for measuring Voltage
Current Transformers (CTs) … for measuring Current
…Sometimes
Uninterruptible Power Supply (UPS)… for Powering Relay when
grid goes down (not required in all systems)
“I thought inverters had voltage/frequency trip
setpoints??!!
They do. Required when utility desires
Additional or Redundant protection
Made by companies like SEL, ABB, Cooper, GE,
…
ANSI Device Numbers
“Standard numbers used by utilities/relay companies to
indicate protective function”
From PVI 50-100 Installation Manual
Example One Line
…Showing Protective
Relay w/ ANSI Device
Numbers
Utility Control
What is SCADA?
“Supervisory Control and Data Acquisition”
= Control and Monitoring
What would utility want to control?
On/Off (Remote shut down)
Ramp rate
Real Power/Reactive Power/PF
How is this implemented?
Control of Interconnection Breaker
24V Remote Shutdown
Shunt Trip
Modbus RTU, Modbus TCP, DNP3
Utility usually interfaces with inverters
through RTU’s, Protective Relays, Plant
Controller
Example One Line
INVERTERS
INVERTERS
INVERTERS
…Showing a bunch of
equipment
I
Medium Voltage
Projects
TOP RECOMMENDATIONS
1.
Work closely with your utility
Due to requirements for:
Transformer Winding Configuration
Switchgear
Relaying
UPS
Consider requesting
courtesy progress inspection
2.
Work closely with your Inverter
Applications Engineer
Transformer requirements,
design optimization, product
recommendations…
You
Utility Engineer
Medium Voltage
Architectures
600V vs. 1000V
 More modules per string means less strings,
combiner boxes, home runs
 Less strings and home runs means less
losses
Radial vs. Loop Feed
Radial Feed Architecture
SGI 500XT-1000V and
SGI 750XT-1000V
Loop Feed Architecture
Medium Voltage
Design
Considerations
Fixed vs. Tracker
Inter-Row Separation (Power Density)
Oversizing
Other Medium Voltage
Design Considerations
Wood vs. Metal Racking
Bird House Placement
Livestock Considerations
Effective Grounding
of PV inverters
Non-Grounded
CB
Synchronous
DG
Distribution
Feeder
CLOSED
OPEN
Load
VVa b= =VV
b c==V173%
c = 100%
SLG
Fault
Sync. Gen.
Consider an islanded operation where the grid is disconnected and a single line to
ground fault is applied to the island.
Generator neutral shift generates the over-voltages on unfaulted phases.
Single phase loads can be damaged from the overvoltage.
Solidly Grounding Synchronous
CB
Distribution
DG
CLOSED
OPEN
Feeder
Load
VaV=b =VbVc==V100%
c = 100%
SLG
Fault
Sync. Gen.
Grounding the generator neutral prevents over-voltages on unfaulted phases.
Effective Grounding allows 125% over-voltage and impedance grounding
(for protection relay coordination)
Ref: IEEE Std. 142, IEEE Std. C62.92 series
Does same happen with PV inverters?
Distribution
Feeder
CB
CLOSED
OPEN
Load
VaV=b =VbVc==V100%
c = 100%
SLG
Fault
PV Inverter
Even without the inverter neutral grounding (3-wire connection), over-voltage
will not be generated if the load is predominantly wye-connected.
In contrast to the synchronous generator, a PV Inverter is a current source and
no overvoltage will be generated due to the neutral shifting.
“… When the inverter-based DG is isolated from the utility voltage source, there is no
derived neutral shift.”
- Dr. Michael Ropp, 39th Annual Western Protective Relay Conference, Oct. 2012.
PV inverter with pure delta
CB
loads
Distribution
Feeder
CLOSED
OPEN
Load
VVa b= =VV
b c==V173%
c = 100%
SLG
Fault
PV Inverter
Solectria’s simulation results showed a negligible voltage rise in unfaulted phases with
50% delta load and 50% wye grounded loads. With 80% delta-connected load, phase
voltages went up to 120%, which is still less than the maximum over-voltage with the
effective grounding. (125%)
In practical cases, most of the loads will be wye grounded in 3-phase 4-wire system.
Industry Trends
 Several utilities require effective grounding by meeting X0/X1 ratio
1.5 < X0/X1 < 2.5
NGRID, HECO, XCEL, PEPCO, BGE, Indianapolis…
 Some utilities use separate guidelines for inverter based distribution generation(DG)
which makes more sense as the inverter characteristics is quite different from the
rotating machine type generators
XDG0 = 0.6*Zbase +/- 10%
GMP, Hydro One…
 “effectiveness” of effective grounding of inverters is being debated in the PV industry
and there is no consensus yet.
 Solectria uses short circuit test results to define X1 and provides zero sequence (X0 )
impedance table when project requires effective grounding.
Suggested Design Practice
Case 1. PV plant effective grounding with one or multiple inverters (universal solution)
Grounding
Bank
51G
 Minimal hardware and installation cost
 Need to coordinate with the main circuit breaker
 Can be used with any medium voltage transformer configuration
Grounding bank (transformer)
Grounding
bank
51G
PV Inverter
 A grounding bank is a small special transformer configured in Zig-Zag or Delta-Wye.
 A grounding bank is external to PV inverters and provides effective grounding, so
that it does not impact the inverters transformer life.
 A single grounding bank can provide effective grounding for a large PV plant, which
minimizes the installation cost.
 For a SGI 500kW inverter installed at 480V distribution feeder, grounding bank cost
can be several $K.
Suggested Design Practice
Case 2. PV plant effective grounding with grounding inductor and a dedicated wye-delta MV Transformer
Grounding
inductor
51G
 Can be used with a wye-delta medium voltage transformer only
 Can be effectively grounded with a grounding bank also
 Minimal hardware and installation cost
Suggested Design Practice
Case 3. Effective grounding of a single PV inverter using a grounding inductor on an existing electrical service
Grounding
inductor
51G
 Neutral current will flow through the internal transformer, but the current magnitude
is relative low as the grounding inductor provides impedance.
 PV inverter internal magnetic contactor can be used for overcurrent protection
Suggested Design Practice
Case 4. Solid grounding of a single PV inverter
(not recommended for sites with more than 2 inverters)
51G
 Neutral current will continuously flow through the internal transformer.
 Configuration is not recommended for sites with more than 2 inverters.
 Heat generation and unwanted losses inside the internal transformer.
 Configuration is not recommended as it can desensitize the utility side fault current
protection (MV level).
Effective Grounding Summary
Most 3-phase 4-wire systems support single phase loads, which puts the effective grounding requirement for
PV inverters in question.
Many utilities request effective grounding with a controlled impedance for relay protection coordination.
Solectria provides impedance tables for all commercial and utility scale PV inverters to help customers design
an effectively grounded PV system.
Effective grounding using Zig-Zag transformer is a universal solution for ungrounded DG.
Many Solectria inverters have an internal wye-delta isolation transformer with a neutral connection which can
be used to provide effective grounding. When used, neutral over-current protection is strongly recommended.
Smart Inverters
Power Curtailment
80kW  50kW  80kW
90
Power in KW
80
70
60
50
Pcmd
40
Pout
30
50
60
70
80
percentage
90
100
Advantages of Power Curtailment
100kW interconnection Limit
700k
W
~50k
W
750k
W
PLC
Monday through Friday
Advantages of Power Curtailment
•
100kW interconnection Limit
70kW
~100kW
170k
W
23% limit
PLC
Saturday and Sunday
Inverter Capacity for VARs
Inverter and AC interconnection have to be sized to carry both real
and reactive current
156 kVAr
Example: 500kVA @ 0.95 PF
475 kW
Inverter Capacity for VARs
Inverter and AC interconnection have to be sized to carry both real
and reactive current
156 kVAr
Example: 500kVA @ 0.95 PF
475 kW
475 kW
Inverter Capacity Allocation for VARs
Inverter and AC interconnection have to be sized to carry both real
and reactive current
Example: 500kVA @ 0.95 PF
156 kVAr
475 kW
475 kW
Inverter Capacity Allocation for VARs
0.8
0.6
Q Reactive p.u.
0.4
0.2
0
0
0.2
0.4
0.6
-0.2
-0.4
-0.6
-0.8
 Power factor control = +/- 0.8 (+/- 0.95 preferred)
 Maximum reactive power control = 60%
 May require power curtailment for reactive power control
 May conflict with the islanding detection
P Active p.u.
0.8
1
VAR support
(remote utility option)
1000
800
600
400
200
0
-720
-630
-540
-450
-360
-270
-180
-90
0
90
180
270
360
-200
-400
-600
-800
-1000
voltage
current
power (rms)
real power (rms)
• PPA owned (“in front of the fence”)
o UL1741 enforces a PF > 0.95
450
540
630
720
Reactive Power Control
The waveform shows instantaneous transient response of the inverter
output current (red) from full inductive to full capacitive.
DNP3 Compliant Smart Grid
Inverters
High Penetration Scenario
Example:
1.7 MW site in Cedarville NJ
4.7 miles from substation 12kV feeder, 6MW mid-day load
Concerns of local overvoltage
Utility has closed circuit for more PV
1.7 MW
0.5 MW
Overvoltage Concerns
3.0% of points
exceed +5% limit
The effect of reactive power on
distribution lines
VAR Generation
PCC voltage is being
pushed up.
VAR Absorption
PCC voltage is being
pulled down.
Example: PF control
Feeder could be reopened for PV after PF adjustment to 0.97
“Flicker” Mitigation (cloud induced voltage transients)
< 0.1% of points
exceed 5% limit
Benefit to Utility
Example: Volt-VAR
control
• Reduced wear out of electromechanical voltage regulators
• Flatter voltage profile overall
Possible additional
Voltage Regulator
action
Inverter Volt-Var Control
20% PV Penetration
Baseline – No PV
Medium Voltage
Showcase Projects
Case Study – True North
Largest Solar Site in New England (4.75MW)
Product: MSS 1MW x5
System Size
4.75 MW
Modules
Canadian Solar
Installer
Mastek Renewables
Location
Salisbury, MA
IND Airport Solar Farm
Largest Airport Installation in
the World Product: (20) SGI 500XT
System Size
10MW
Installer
Location
Indianapolis, Indiana
Modules
44,128 Sharp 280W
Entropy North Carolina Solar
Product: (69) SGI 500XTM
Farms
System Size
34.5 MW AC
Installer
Location
Various Sites in NC
Modules
Canadian Solar 305W
Case Study – Xcel Energy
Product: 504, PVI 82KW – SCADA controlled, VAR supports
System Size
30 MW
Modules
Amonix
Installer
Amonix, Cogentrix
Location
Alamosa, CO
Arc Fault & Rapid Shutdown
ARCCOM
Arc-Fault Enabled String Combiners
• ARCCOM-16X & ARCCOM-24X
16 or 24 Fused Inputs
• Critical Component for:
• Arc Fault (690.11)
• Rapid Shutdown (690.12)
• Fuse Servicing Disconnects
(690.16)
What is an arc-fault?
Current
Healthy Wire
•
Current
The same amount of current must flow through a smaller conductor
Conductor heats up and eventually melts
Current
•
•
Air Ionizes and plasma allows current to flow across the gap
Temperatures can reach 9000 degrees Fahrenheit
New/Imminent Code
Requirements
NEC 2011
Arc Fault on Rooftops (690.11)
Fuse Servicing Disconnects
(690.16)
NEC 2014
Arc Fault Everywhere (690.11)
Grounded Conductor Ground Fault
(690.5)
Rapid Shutdown (690.12)
New/Imminent Code
Requirements
Inside the ARCCOM
Optional 120Vac
Power Supply
DC Vacuum
Contactor
Optional Type 2
DC SPD
Finger Safe Fuse
Holders
Arc Fault
Detection
Circuitry
DC Conduit Entry Location
690.12 (C) Facilities with Rapid Shutdown PV system
circuits installed on or in buildings shall include a rapid
shutdown function that controls specific conductors in
accordance with 690.12(1) through (5) as follows.
(1) Requirements for controlled conductors shall apply only to PV system conductors of
more than 1.5m (5 ft) in length inside a building , or more than 3m (10 ft) from a PV
array.
(2) Controlled Conductors shall be limited to not more than 30V and 240 volt-amperes
within 10 seconds of rapid shutdown initiation.
(3) Voltage and power shall be measured between any conductor and ground
(4) The rapid shutdown initiation methods shall be labeled in accordance with 690.56(B)
(5) Equipment that performs the rapid shutdown shall be listed and identified.
To Inverter
10 ft boundry
ON
ON
To Inverter
ON
ON
10 ft boundry
24V
dc
OFF
OFF
To Inverter
OFF
OFF
10 ft boundry
24V
dc
DC Bus Capacitance
SGI, SGI XT, and SGI XTM all have DC Vacuum Contactors
DC Contactors in the inverter
ON
open when AC is off
ON
ON
ON
ON
ON
24V
dc
AC
Disconnect
DC Bus Capacitance
SGI, SGI XT, and SGI XTM all have DC Vacuum Contactors
DC Contactors in the inverter
OFF
open when AC is off
OFF
OFF
OFF
OFF
OFF
24V
dc
AC
Disconnect
DC Bus Capacitance
SGI, SGI XT, and SGI XTM all have DC Vacuum Contactors
DC Contactors in the inverter
OFF
open when AC is off
OFF
OFF
OFF
OFF
OFF
24V
dc
AC
Disconnect
ON
To Panelboard
ON
ON
ON
10 ft boundary
AC
Disconnect
OFF
To Panelboard
OFF
OFF
OFF
10 ft boundary
AC
Disconnect
690.56 Identification of Power Sources.
(C) Facilities with Rapid Shutdown
Buildings or structures with both utility service
and a PV system complying with 690.12 shall
have a permanent plaque or directory
including the following wording:
PHOTOVOLTAIC SYSTEM EQUIPPED
WITH RAPID SHUTDOWN
The plaque or directory shall be reflective,
with letters capitalized and having a minimum
height of 9.5mm (3/8 in.), in white on red
background.
Where do you put
this?
Arc-Fault Detection

Detection based on telltale frequency characteristics

Inverters generate noise in the same range

UL 1699B
Source- Implementing Arc Detection in Solar Applications
Brett Novak, Texas Instruments
:690.11 ARC-Fault Circuit Protection (Direct Current)
Photovoltaic Systems with dc source circuits, dc output circuits, or both, operating at
a PV system maximum system voltage of 80 volts or greater, shall be protected by a
listed (dc) arc-fault circuit interrupter, PV type, or other system components listed to
provide equivalent protection. The PV arc-fault protection means shall comply with
the following requirements
(1) The system shall detect and interrupt arcing faults resulting from a failure in
the intended continuity of a conductor, connection, module, or other system
component in the dc PV source and dc PV output circuits.
(2) The system shall require that the disabled or disconnected equipment be
manually restarted.
(3) The system shall have an annunciator that provides a visual indication that the
circuit interrupter has operated. This indication shall not reset automatically.
690.11 ARC-Fault Circuit Protection (Direct Current)
Photovoltaic Systems with dc source circuits, dc output
circuits, or both, operating at a PV system maximum
system voltage of 80 volts or greater, shall be protected
by a listed (dc) arc-fault circuit interrupter, PV type, or
other system components listed to provide equivalent
protection. The PV arc-fault protection means shall
comply with the following requirements:
(1) The system shall detect and interrupt arcing faults resulting from a failure in
the intended continuity of a conductor, connection, module, or other system
component in the dc PV source and dc PV output circuits.
(2) The system shall require that the disabled or disconnected equipment be
manually restarted.
(3) The system shall have an annunciator that provides a visual indication that the
circuit interrupter has operated. This indication shall not reset automatically.
Maximize SNR to Minimize Nuisance
Tripping
• NEC 690.11 requires manual reset
• Every arc-fault trip requires a truck roll
• ARCCOM has undergone 1 year of
product compatibility testing to minimize
nuisance tripping.
• Single sensor, reflection based
technology is significantly more prone
to nuisance tripping and more costly to
maintain
String Level
Detection
Three-Phase String Inverters
PVI 23TL, 28TL, 36TL
Introducing the PVI
23/28/36TL
Yes!
23kW
480V 3ɸ/4W
Dual 480V-800V MPPT
8 fused inputs
98% CEC
28kW
480V 3ɸ/4W
Dual 500V-800V MPPT
8 fused inputs
98% CEC
36kW
480V 3ɸ/4W
Dual 540V-800V MPPT
8 fused inputs
98% CEC
Recommended OCPD
Yes!
23kW
480V 3ɸ/4W
27.7A
28kW
480V 3ɸ/4W
38.5A
36kW
480V 3ɸ/4W
43.3A
35A OCPD
45A OCPD
55A OCPD
Note: new max. output current values
Introducing the PVI 23TL, 28TL, 36TL
New for 2015
• Prototype Arriving January 2015
Yes!
• Pricing Available February 2015
• Shipping Product June 2015
• Same
Wiring Box as 23TL, 28kW
28TL
23kW
480V 3ɸ/4W
480V 3ɸ/4W
Dual 500V-800V MPPT
Dual 480V-800V MPPT
• Similar
Size, Weight, and
Footprint
8 fused
inputs
8 fused inputs
98%
CEC heavier)
(Maybe
an inch taller and
10lbs
98% CEC
50A Breaker
40A Breaker
36kW
480V 3ɸ/4W
Dual 500V-800V MPPT
8 fused inputs
98% CEC
Topology and
Design
Inverter Topology
DC Input and Filtering
*DC +/- Fusing Not Shown
Boost
Stage
Inverter
Circuit
AC Filtering and Output
Electrical/Performance
Benefits
Dual MPPT Zones
PVI 23TLM >>> 2 x 11.5kW MPPT Zones
PVI 28TLM >>> 2 x 14kW MPPT Zones
PVI 36TLM >>> 2 x 18kW MPPT Zones
Design Flexibility – Strings of
different tilt, orientation, length,
module type per zone, shading,
snow zones
Increased Performance –
Reduced mismatch losses
Ease of Installation
and Service
Compact and Lightweight
Weight: 122lbs
Can be lifted and
mounted by two
people!
Mount to:
Exterior, Interior,
or Parapet Walls,
Racking Structure,
Carport Frame
Save on inverter
pad cost!
Easy to Install
Connectorized Wiring Box
• Zero Wires to Connect
• Fast and Simple Installation & Removal
1
2
3
1
2
3
Mounting Considerations
90º - 15º tilt
for placement versatility
Mounting Considerations
Bentek
AET
Wiring Box
Wiring Box with No Options, prior
to recent upgrades
All fuses are touch safe
DC Disconnect Cover
(cost adder)
Transparent
protection cover
New Wiring Box with Available
AC Disconnect Cover
Options
(cost adder)
SolrenView
Hardware
(cost adder)
DC fuse holder
30A 1000Vdc, 16 poles
For cable 4AWG max
Entrance
for 1.25”
conduit
Partition insulator between
DC cable and AC cable
Entrance
for 1.25”
conduit
AC terminal block
150A 600Vdc, 4 poles
For cable 4AWG max
Bypass Lug Options
Dual MPPT
Combined MPPT
Bottom of Wiring Box – PVI 23-28TL
Knockout for 1” & 1.25” conduit
5 spots for DC & AC cable
Knockout for ¾” conduit
for communications cable
AC & DC Disconnect
Cover Option
AC & DC Disconnect Cover
Option
DC
Disconnect
AC
Disconnect
DC or
AC & DC Disconnect Cover
Installation
Only a non-locking tamper-resistant cover is offered
Offered due to customer request at accessible sites
Locking not offered in case fire department needs to access
the disconnect
Shade Cover Option
Shade Cover
•
•
•
•
•
•
Simple, quick (<10 minute install)
o
Only 1 person needed
o
Easy on/off cover
o
Lower mount - installed with nuts/bolts
o
Upper Mount - No tools required, hand mount tool
Especially for 15 degree mounting in sun
Simple cover helps protect inverter
Powder coated steel
Light weight (~15 pounds)
Fold up/hinged lower section for easy LCD/Key Pad access
PVEvolutionLabs Testing Results
Sunshield will:
Protect the inverter against
harsh weather and direct
sunlight/very hot temperatures
Reduce thermal gain on
inverter chassis
(= lower operating temps)
Increase energy harvest by
preventing derating
Results:
Lower Temperature
1% More Energy
3% Higher Power
Engineered to Maximize Uptime
Choice of swapping
entire inverter or only
top section for service.
Replacement unit is
provided for field swap
of down unit.
Standard 10 year
warranty (15 and 20
year options available)
Safety, Code, and
Other Requirements
New/Imminent Code
Requirements
NEC 2011
Arc Fault on Rooftops (690.11)
Fuse Servicing Disconnects
(690.16)
NEC 2014
Grounded Conductor Ground
Fault (690.5)
Rapid Shutdown (690.12)
Arc Fault Everywhere (690.11)
NEC Compliance
PVI 3ɸ-string inverters are listed to UL1741 for use with
ungrounded/floating arrays (only)
Ungrounded systems must comply with NEC 690.35:
“Ungrounded Photovoltaic Power Systems”

Even though array is “Ungrounded,” DC Equipment
Grounding of metal frames, racking, exposed metal
parts is still required

PV Wire on module and exposed cable instead of
USE-2 [690.35(D)]
Far Niente Winery, Oakville, CA,
~400kW across land and lake
NEC Compliance
Disconnecting Means
Integrated DC Disconnect opens both
(+) and (-) Poles of the Array.
[690.35(A), 690.13]
NEC Compliance
Overcurrent Protection
Fusing on both (+) and (-) inputs [690.35(B), 690.9].
Inverter
Connection
Box
Positive
Bus
Negative
Bus
* Only 1 MPP tracker shown
Ground Fault Detection

PVI 3ɸ-string inverters have residual ground fault detection.
 Shorter DC runs decreases likelihood of ground fault.

2014 NEC requires grounded conductor (Blind-spot) ground fault
detection.

During ground fault only 3ɸ inverter
is taken offline rather than the
entire array.
 Better system uptime
 More focused troubleshooting
Figure from “Ungrounded PV Power Systems in the NEC,”
SolarPro, Aug./Sept. 2012
Arc-Fault Detection

PVI 3ɸ-String Inverters have integrated arc-fault detection.


Detection based on telltale frequency characteristics
Fault is isolated to one inverter
Source- Implementing Arc Detection in Solar Applications
Brett Novak, Texas Instruments
Rapid Shutdown –
2014 NEC 690.12
Applies to PV systems
on buildings
Shutdown of circuits
10ft from array
5ft inside a building
Less than 30V and
240VA in 10 sec.
(Between any two
conductors and between
any conductor and
ground)
Signage requirements
Listed and identified
equipment
2014 NEC Compliance by Shutdown at String Inverter
ON
To Panelboard
ON
ON
ON
10 ft boundary
AC Disconnect
2014 NEC Compliance by Shutdown at String Inverter
OFF
To Panelboard
OFF
OFF
OFF
10 ft boundary
AC Disconnect
Effective Grounding
PVI 3ɸ-String Inverters
 Require grounding transformer for
effective grounding,
 Zig-Zag or Yg-Δ
 Only one grounding bank
needed for each service
Our Power Systems Team has
developed a calculator to
define Zig-Zag Ratings
PVI 23TL, 28TL, 36TL
Monitoring Flexibility
Solectria’s Web Based Monitoring Software
 Benefit: Work with one
company for monitoring and
inverter
 Benefit: Site visibility by
Solectria Service and Apps
for troubleshooting system
issues
 Download Data
 Create email fault
notifications (email or SMS)
 Kiosk View - Standard
 Upgrade Options:
Reporting Services (with
Revenue Grade Meter)
Configuration 1: Daisy Chaining via Modbus RTU/RS-485
 Requires at least one PVI TL/TLM with SolrenView Board.
 All inverters are displayed on same SolrenView site
SolrenView
Board
RS-485
RS-485
RS-485
Max 16 devices, 1,500 ft*
Ethernet
Cable
(300ft max)
To LAN
*More devices/longer network length possible in low noise environment or with use or isolator/repeaters)
Revenue Grade Metering and Reporting
 Monitor the combined output of
multiple inverters with revenue
grade accuracy (1%)
 Agency Reporting Option through
Solectria SolrenView Software
Inline Fusing
Meter Body
 Meter kit installed in downstream
panel or CT cabinet (enclosure
provided by customer)
Current Transducers
(CT’s)
Voltage Sensing
Leads
Example: Multiple Inverters w/ RGM
RS-485 Termination Resistor
 The inverter furthest away from the gateway needs its termination resistor set.
 The termination resistor helps maintain data signal quality and prevents Ghost Data
RS-485 Termination Resistor
 The inverter furthest away from the gateway needs the termination resistor enabled.
S402
On means the
termination resistor
is enabled
 The termination resistor helps maintain data signal quality and prevents Ghost Data
Temperature Derating
Voltage Derating
Potential Induced Degradation (PID)
3ɸ-String Inverters – Ungrounded Arrays/Bipolar
 Ungrounded arrays may be susceptible to PID.
 PID “offset” box can be used to reverse the effects of PID
Central Inverters – Grounded Arrays
 Grounded Arrays do not experience PID.
N-Type
P-Type
+
Glass
+
-
+
+
-
+
Frame
Replacement of Legacy Inverters



600V DC
208V, 240V, 480V
6 fused inputs
Old arrays are typically wired with USE-2 conductors
TL inverters operate ungrounded and require PV wire (690.35)
Old modules designed for grounded arrays should stay grounded
Using a TL inverter will create PID production losses
Thank you!
/SolectriaRenewables
@SolectriaRen
Solectria Renewables, LLC
Solectria –
A Yaskawa Company
/105590461511696994974
360 Merrimack Street
Building 9, 2nd Floor
Lawrence, MA 01843
/SolectriaRenewables0