2012 Jim Dunlop Solar
Chapter 8
Inverters
Definitions and Terminology ● Types and
Applications ● Functions and Features ● Selection
and Sizing ● Monitoring and Communications
2012 Jim Dunlop Solar Inverters: 8 - 2
Overview
Defining the purpose for inverters in PV systems and other
applications.
Identifying basic electrical properties, waveforms and their
characteristics relative to inverter design and operation.
Explaining the basic types of inverter circuit designs and their
components.
Understanding the differences in operating principles and
specifications for stand-alone and interactive inverters.
Identifying key specifications and ratings for interactive inverters
required for systems design and installation.
2012 Jim Dunlop Solar Inverters: 8 - 3
Inverters
Inverters are used in PV systems to convert direct current (DC)
power from batteries or PV arrays into alternating current (AC)
power.
Other inverter applications include:
Fuel cells
Wind turbines and microturbines
Variable-frequency drives
Uninterruptible power supplies
Electronic ballasts and induction heaters
HVDC power transmission
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Inverters
Inverters are used in PV systems
to convert direct current (DC)
power from batteries or PV arrays
into alternating current (AC)
power.
The first inverters/converters
used motor-generator sets, but
were costly, heavy and inefficient.
Modern inverters use solid-state
designs and microprocessor
controls to produce high quality
AC power very efficiently.
SMA
TEMco
Rotary Converter
Solid-State Inverter
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Electrical Properties
Basic electrical properties and principles are fundamental to
understanding how inverters are designed and operate,
including:
Direct current and alternating current
Waveform types and parameters
Power and energy
Ohm’s law
Single-phase and three-phase power
Resistive and reactive loads
Real, apparent and reactive power
Power quality
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Direct-Current (DC)
Direct current (DC) is a unidirectional flow of electrical charge
that does not vary in polarity between positive and negative
values over time.
Solar cells and batteries are examples of DC devices.
Most electronic circuits also operate on DC power.
DC circuits are defined by a positive and negative polarity, or
poles. Electrons flow in one direction.
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Alternating Current (AC)
Alternating current (AC) is an oscillating flow of electrical charge
that periodically changes direction over time.
In an AC circuit, the two poles alternate between negative and
positive, continually reversing direction of the electron flow.
The changing polarity of AC over time is what distinguishes it
from DC.
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Waveforms
A waveform is graphical representation of how electrical
properties vary over time, for example with current and voltage.
Current and voltage for both DC and AC circuits can be
mathematically described by their waveform.
A periodic waveform repeats itself at regular intervals.
A cycle is a complete waveform set that repeats itself over time.
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DC Waveforms
Time >
0
Full wave rectifier
Half wave rectifier
Battery
0
0
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AC Waveforms
Time >
Sine Wave
0
Modified Square Wave
Square Wave
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Sine Waves
A sine wave is a periodic waveform commonly associated with
rotating generators and AC power systems.
Time >>
3π/2 (270°)
π (180°)
π/2 (90°)
2π (360°)
φ
Animation
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AC Waveform Properties
Time = 0
<< Negative 0 Positive >>
Peak to Peak
Amplitude
(peak)
One Cycle = 360 deg or 2π radians of phase angle
Voltage
Time >>
170 V peak
120 V rms
At frequency of 60 Hz, period is 1/60 sec (16.67 msec)
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Frequency
Frequency is the number of alternating current waveform cycles
that repeat in one second, expressed in units of hertz (Hz).
The frequency of the U.S electric grid is maintained at 60 Hz,
while 50 Hz is used in Europe and Asia.
Frequency establishes the speed of AC motors and generators,
and a critical parameter in synchronizing electrical utility
systems.
The period is the time it takes a waveform to complete one full
cycle before it repeats itself.
Period is the inverse of frequency.
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Peak and RMS Voltages
One cycle: 360°
Time >>
0
Sine wave has V
peak
= V
RMS
x √2
120
Voltage
170
Square wave has V
peak
= V
RMS
-170
-120
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True RMS Meters
Fluke 179
Fluke 87V
Fluke 337
Fluke
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Resistive Circuits
One cycle: 360°
Time >>
voltage
current
0
power
Positive >>
<< negative
Phase angle between current and voltage waveforms
equals zero, and power factor equals unity.
Voltage
Current
Power
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Time >>
Inductive Circuits
One cycle: 360°
0
voltage
current
Positive >>
<< Negative
Positive power
consumed by load
Negative power
returned to source
Phase angle between current and voltage waveforms
greater than zero, power factor is less than unity.
Voltage
Current
Power
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Inductive Circuits
voltage
current
Animation
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Power Quality
AC loads are designed to operate at prescribed voltage, phase
and frequency.
Power quality are effects that alter a nominal waveform
characteristics, including:
Power factor
Voltage regulation (sag and surges)
Frequency regulation
Voltage and phase imbalance
Harmonic distortion
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Oscilloscopes and
Power Quality Analyzers
Fluke 190 ScopeMeter
®
Fluke 43B Power Quality Analyzer
Fluke
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Harmonics
Time >
3
rd
harmonic
0
5
th
harmonic
Combination of fundamental &
3
rd
and 5
th
harmonic
Fundamental frequency
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Power and Energy
Power is the rate of transferring work or energy, and analogous to:
An hourly wage ($/hr)
Speed of a vehicle (mi/hr)
Water flow (gal/hr)
Energy is the total amount of work performed over time, and analogous
to:
Income earned ($)
Distance traveled (mi)
Water volume (gal)
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Power and Energy
Electrical power is expressed in units of watts (W).
1 megawatt (MW) = 1,000 kilowatts (kW) = 1,000,000 watts (W)
Electrical energy is expressed in units of watt-hours (Wh).
1 kilowatt-hour (kWh) = 1000 Wh
where
= energy (Wh)
= average power (W)
= time (hrs)
avg
avg
EP t
E
P
t
= ×
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Ohm’s Law
Ohm’s law defines the
relationships between voltage,
current and resistance in
electrical circuits.
By definition, a current of one
ampere passing through a
resistance of one ohm results in
a potential difference of one volt.
1 Volt = 1 Amp x 1 Ohm
Ohm's law can be expressed in
various forms:
where
= voltage (V)
= current (A)
= resistance ( )
V IR
V
I
R
V
R
I
V
I
R
= ×
=
=
Ω
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Power and Ohm’s Law
In DC circuits, electrical power is
equal to the product of the voltage
and current:
Power (W) = Voltage (V) x Current (A)
Power can be calculated in different
ways using Ohm’s law:
2
2
where
= power (W)
= voltage (V)
= current (A)
= resistance ( )
PVI
PI R
V
P
R
P
V
I
R
= ×
= ×
=
Ω
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Ohm’s Law Wheel
R
Resistance
(ohms)
V
Voltage
(volts)
I
Current
(amperes)
P
Power
(watts)
P
I
IR⋅
PR⋅
V
I
2
V
P
2
P
I
VI⋅
2
IR⋅
2
V
R
P
V
V
R
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Power in AC Circuits
The calculation of real power in AC
circuits takes into account the phase
angle difference between the current
and voltage waveforms.
In AC circuits, the product of RMS
voltage and current is called
apparent power:
Volts x Amps = Apparent Power (VA)
Power factor is the ratio of real
power to the apparent power and
equal to the cosine of the phase
angle:
PF = Cos θ
cos
where
= power (W)
= voltage (V)
= current (A)
= phase angle (deg)
cos = power factor (0-1)
In 3-phase circuits:
cos 3
PVI
P V I PF
P
V
I
PVI
θ
θ
θ
θ
= ××
= ××
= ×× ×
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Power Triangle
Apparent Power, S
(volt-amperes, VA)
Reactive Power, Q
(volt-amperes reactive, VAR)
True Power, P (watts, W)
θ= phase angle between
voltage and current waveforms
22
QPS +=
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Transformers
Transformers are used in PV inverters to convert AC voltage from
one level to another and to isolate the DC input from and AC
output.
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Transformers
The turns ratio is the ratio of the number of coils in a
transformer’s primary and secondary windings, and defines the
ratio of primary and secondary voltages.
For an ideal transformer, the ratio of the currents in the primary
and secondary circuits is inversely proportional to the turns
ratio.
112
221
12
12
12
where
and = number of turns in primary and secondary windings
and = voltage in primary and secondary windings
and = voltage in primary and secondary windings
NVI
NVI
NN
VV
II
= =
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Autotransformers
Autotransformers can be used to adjust inverter AC output
voltage from one level to another, but provide no isolation
because they use the same winding.
Primary:
240 V
Secondary:
208 V
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Types of Power Systems
Single-Phase Systems
Spilt-phase systems are commonly used for residential and small
commercial electrical services derived from a single-phase source.
Three-Phase Systems
Wye “Y” or “star” configuration
Delta “Δ” configuration
An understanding of different types of electrical services and
their compatibility with inverter output specifications is an
important aspect of designing and installing grid-connected PV
systems.
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Single-Phase Power Systems
Single-phase power sources have only one voltage waveform.
Split-phase power systems are single-phase power systems providing
multiple load voltages by center-tapping distribution transformers.
120 V~
∠=0°
120 V~
∠=180°
240 V
I
L2
L1
N
L2
I
L1
I
N
=I
L1
-I
l2
4,160 V – 35 kV
∠=0°
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One cycle: 360°
Time >>
Voltage
Three-Phase Power
0
Positive >>
<< Negative
Phase angle between voltage waveforms in 3-phase
motors and generators is 120 degrees.
Phase A
Phase B
Phase C
At 60 Hz = 1 cycle takes 1/60 second
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Wye Configuration
Wye “Y” Configuration
Phase and line currents are always equal.
For a balanced load, the line voltage between any two phases is equal to
the phase voltage x √3.
A
B
C
I
N
I
A
=I
L1
L1
L2
L3
N
I
C
=I
L3
I
B
=I
L2
120 V~
∠=0°
120 V~
∠=120°
120 V~
∠=240°
120 V
208 V
4-Wire, 120208 V - Wye “Y”
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Delta Configuration
Delta “Δ” Configuration
Line voltage and phase voltages are equal.
For a balanced load, the line current is equal to the phase current x √3.
L1
L2
L3
A
B
C
I
AB
I
BC
I
CA
I
L1
I
L2
I
L3
240 V~
∠=0°
240 V~
∠=240°
240 V~
∠=120°
240 V
240 V
3-Wire, 240 V Delta “Δ”
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Wye and Delta Configurations
3-Wire, 240 V Delta “Δ” 4-Wire, 120208 V - Wye “Y”
L1
L2
L3
A
B
C
I
AB
I
BC
I
CA
I
L1
I
L2
I
L3
240 V~
∠=0°
240 V~
∠=240°
240 V~
∠=120°
240 V
240 V
A
B
C
I
N
I
A
=I
L1
L1
L2
L3
N
I
C
=I
L3
I
B
=I
L2
120 V~
∠=0°
120 V~
∠=120°
120 V~
∠=240°
120 V
208 V
2012 Jim Dunlop Solar Inverters: 8 - 38
High-Leg Delta Configuration
A high-leg delta configuration center taps one winding for a ground and
neutral connection, providing 120 V and 240 V single-phase and 240 V
three-phase.
240 V, 4-Wire High-Leg Delta “Δ”
A
B C
240 V~
240 V
208 V
240 V~
120 V 120 V
240 V
240 V
L1
L2
L3
Neutral
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Three-Phase Power
Animation
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Inverter Circuit Designs
Inverters produce AC power output from DC power input using
different circuit designs and components.
Inverter
DC Power In
AC Power Out
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Switching Elements
Thyristors and Silicon Controlled Rectifiers (SCRs)
Metal-Oxide Field-Effect Transistors (MOSFETs)
Insulated Gate Bi-polar Transistors (IGBTs)
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Switching Control
Line-commutated inverters use an external source, such as the
utility grid to trigger switching elements and synchronize their
output.
Used for grid-connected inverters only.
Self-commutated inverters control switching elements and
regulate their waveform output with internal software and
controls.
Used for stand-alone or interactive inverters.
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H-Bridge Inverter
H-Bridge Square Wave Inverter
DC input
Negative (-)
Positive (+)
3
AC output
1 2
4
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H-Bridge Square Wave Inverter
One cycle
Time >>
Current
0
Positive >>
<< Negative
For 60 Hz, 1 cycle is 1/60
th
second,
switching occurs every 1/30
th
second.
Switches 1 and 4 closed, 2 and 3 open
Switches 1 and 4 open, 2 and 3 closed
DC input
(blue line)
AC output
(red line)
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H-Bridge Inverter
H-Bridge Square Wave Inverter
DC input
Negative (-)
Positive (+)
3
AC output
1 2
4
Animation
2012 Jim Dunlop Solar Inverters: 8 - 46
H-Bridge Inverter
This H-bridge inverter converts 12 VDC into a 120 VAC square
wave using a transformer with a 10:1 turns ratio.
H-Bridge Square Wave Inverter
12 VDC input 120 VAC output
1 2
4 3
Transformer
10:1 Turns Ratio
Switching
elements
Negative (-)
Positive (+)
2012 Jim Dunlop Solar Inverters: 8 - 47
Push-Pull Inverter
Push-Pull Modified Square Wave Inverter
DC input
Positive (+)
SW1
Positive (+)
Transformer
Negative (-)
SW2
AC output
Current flow w/ SW1 closed, SW2 open
Current flow w/ SW1 open, SW2 closed
Shorting
winding
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Low-Frequency Inverters
H-Bridge or
Push-Pull
DC Source
(Battery)
AC Output Transformer
Low-voltage DC Low-voltage AC Higher-voltage AC
Low-frequency inverter designs use an H-bridge or push-pull
inverter circuit, and the resulting AC output is stepped up to
higher voltages through a transformer.
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PWM Control
PWM control regulates the RMS voltage output by varying the
width of the output signal depending on peak voltage available
from the source.
Time >
Voltage
0
+170
-170
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Multistage
Low-Frequency Inverters
H-Bridge
DC Source
(Battery)
Transformer
1:1 ratio
Low-voltage DC
Multistage inverter designs use parallel circuits to synthesize
true sine waves.
Low-voltage AC
H-Bridge AC Output
Transformer
1:3 ratio
H-Bridge
Transformer
1:9 ratio
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PWM Sine Wave Inverters
Pulse-width-modulation (PWM) control is used to simulate multi-
step AC sine waves by superimposing square waves of varying
amplitude and width.
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High-Frequency Inverters
DC-DC
Converter
DC Source H-Bridge
High frequency inverters use DC-DC converters and smaller
transformers, resulting in highly efficient and lightweight
designs.
AC Output
Transformer
PWM Frequency
Regulation
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Types of PV Inverters
Stand-Alone Inverters
Operate from batteries and supply power independent of the utility grid.
Utility-Interactive or Grid-Connected Inverters
Operate from PV arrays and supply power in parallel with the utility grid.
Bi-Modal or Battery-Based Interactive Inverters
Operate as diversionary charge controllers, and produce AC power output
to regulate PV array battery charging when the grid is energized.
Transfer PV system operation to a stand-alone mode and provide backup
electric power to critical loads when the utility grid is not energized
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Stand-Alone & Interactive
Inverters
Battery
Stand-Alone
Inverter
AC Load
PV Array
Interactive
Inverter
Utility Grid
Interactive Operation with PV Array as DC Power Source
AC load is limited by
inverter power rating
PV array size is limited by
inverter power rating
Stand-Alone Operation with Battery as DC Power Source
Vs.
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Stand-Alone Inverters
Stand-alone inverters use batteries for DC power input
PV arrays or other DC sources are used to charge the battery independently.
Common DC input voltage 12 V, 24 V and 48 V for residential application, up to 480
V for industrial applications.
Supply power to AC loads isolated from the grid; inverter power rating
dictates maximum AC load.
Often include battery charger function for utilizing an independent AC
input source (e.g., generator or grid)
Can not synchronize with and feed power back into the grid.
Output power rating must be at least equal to the single largest
connected load [NEC 690.10].
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Stand-Alone Inverters
DC Load PV Array
Battery
Charge
Controller
Stand-Alone
Inverter/Charger
AC Load
AC Source
(to Charger Only)
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Stand-Alone Inverters
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Utility-Interactive Inverters
Interactive inverters use PV arrays for DC power input, and
supply synchronized AC output power in parallel with the utility
grid.
Site AC loads may be served by the inverter output, utility or
both. Excess power not needed by local loads flows to the grid.
Power ratings limit the size of the connected PV array; output is
independent of loads.
All listed interactive inverters produce utility-grade sine wave
output and include anti-islanding safety features to de-energize
inverter output to the grid upon loss of grid voltage.
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Utility-Interactive Inverters
Load
Center
PV Array
Interactive
Inverter
AC Loads
Electric
Utility
2012 Jim Dunlop Solar Inverters: 8 - 60
Types of Interactive Inverters
Module-Level Inverters
200-300 W, includes AC modules and micro inverters integral to or installed at the
PV module level.
String Inverters
2-12 kW, designed for residential and small commercial applications using 1-6
series-connected PV array source circuits.
Central Inverters
30-50 kW up to 500 kW, designed for commercial applications with homogeneous
arrays.
Utility-Scale Inverters
500 kW to 1 MW, designed for solar farms.
Bimodal Inverters
2-10 kW, battery-based interactive inverters that provide grid backup to critical
loads.
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Module-Level Inverters
AC modules are factory-
integrated PV modules with
interactive inverters.
Micro inverters are similar in
concept but are separate
equipment.
Typically 200-300 W rated
maximum AC output (approx. PV
module size).
Used primarily for residential
and small commercial
applications, and can achieve
greater energy harvest from
partially shaded and multi-
directional arrays.
Enphase Micro Inverter
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String Inverters
String inverters are small inverters in the 1 to 12 kW size range,
intended for residential and small commercial applications.
Generally single-phase, usually limited to 1 to 6 parallel-connected source
circuits, or “strings”.
Some integrate source circuit combiners, fuses and disconnects into a
single unit.
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Central Inverters
Central inverters start at 30-50 kW up to 500 kW, and interconnect
to 3-phase grids.
Best suited for homogeneous PV arrays having all the same modules and
source circuit configurations, and aligned and oriented in the same
direction with no shading.
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Utility-Scale Inverters
Most commercial PV inverters up to 500 kW installed on public
and private properties are interconnected to the grid at service
voltages less than 600 VAC.
These systems must comply with NEC requirements and use listed
inverters and other equipment.
PV arrays are less than 600 VDC.
Large inverters 500 kW to 1 MW and higher used in PV power
plant installations are interconnected to the grid at distribution
voltages up to 38 kV.
For utility-controlled sites, certain variances with the NEC and product
listing requirements may apply.
PV arrays may operate up to 1000 VDC
2012 Jim Dunlop Solar Inverters: 8 - 65
Utility-Scale Inverters
Utility-scale inverters use higher
DC input and AC output voltages
to reduce losses, and the size
and costs of the conductors and
switchgear required.
DC input from PV arrays 900 to
1000 VDC
AC output to grid at distribution
level voltages up to 35 kV.
Packaged systems include
inverters, transformers,
switchgear, climate-controlled
enclosure and mounting
platform as a pre-engineered
unit.
2012 Jim Dunlop Solar Inverters: 8 - 66
Bimodal Inverters
Bimodal inverters use batteries for DC power input and may
operate in either interactive or stand-alone mode.
In interactive mode, the inverter produces AC power output in
proportion to PV array production, while maintaining a
prescribed maximum battery voltage.
Upon loss of grid voltage, the inverter automatically transfers to
stand-alone mode, and powers backup loads isolated from grid.
Bimodal inverters may also include load control, battery
charging, and generator starting functions.
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Bimodal Inverters
Bimodal
Inverter/Charger
Critical Load
Sub Panel
Backup
AC Loads
Main Panel
Primary
AC Loads
Electric
Utility
Bypass circuit
Battery PV Array
AC Out AC In
DC
In/out
Charge
Control
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Bimodal Inverters
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Inverter Selection
Selecting and specifying the best inverter for a given application
involves considering the system design and installation
requirements.
Inverter specification sheets are critical.
Inverter selection is often the first consideration in system
design, and based on:
The type of electrical service and voltage.
Anticipated size and locations of the array.
For interactive inverters, optimal DC ratings for the PV array are
110-130% of the inverter maximum continuous AC power output
rating.
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Inverter Specifications
Stand-alone and interactive inverters have similar but different
specifications due to their different application.
Standard specifications for all types of inverters include:
AC output power ratings
DC input voltage
AC output voltage
Power conversion efficiency
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Interactive Inverter Specifications
DC Input
Maximum array voltage (open-circuit, cold)
Recommended maximum array power
Start voltage and operating range
MPPT voltage range
Maximum usable input current
Maximum array and source circuit current
Ground fault and arc fault detection
AC Output
Maximum continuous output power
Maximum continuous output current
Maximum output overcurrent device rating
Power quality
Anti-islanding protection
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Interactive Inverter Specifications
Performance
Nominal and weighted efficiencies
Stand-by losses (nighttime)
Monitoring and communications interface
Physical
Operating temperature range
Size and weight
Mounting locations, enclosure type
Conductor termination sizes and torque specifications
Conduit knockout sizes and configurations
Other Features
Integral DC or AC disconnects
Number of source circuit combiner and fuse/circuit ratings
Standard and extended warranties
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Inverter Standards
UL Std. 1741 Inverters, Converters, Controllers and
Interconnection System Equipment for Use with Distributed
Energy Resources
Applies to both stand-alone and interactive inverters.
IEEE 1547 Standard for Interconnecting Distributed Resources
with Electric Power Systems
Applies to interactive inverters and systems.
National Electrical Code (NEC), NFPA 70
Applies to all inverters and PV system installations.
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Inverter Power Ratings
Both stand-alone and interactive inverters are rated for their
maximum continuous AC power and current output over a
specified temperature range.
Inverter power ratings are limited by the temperature of their
switching elements. Larger inverters use cooling fans.
Stand-alone inverters limit power output by disconnecting AC loads when
their maximum DC input current is exceeded.
Interactive inverters limit their maximum power output by tracking the PV
array off its maximum power point.
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Inverter Power Ratings
Battery
Stand-Alone
Inverter
AC Load
PV Array
Interactive
Inverter
Utility Grid
Interactive Operation with PV Array as DC Power Source
AC load is limited by
inverter power rating
PV array size is limited by
inverter power rating
Stand-Alone Operation with Battery as DC Power Source
Vs.
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Inverter Voltage Ratings
For stand-alone inverters, the DC input voltage is based on a
nominal battery voltage:
Inverters less than 1 kW may use a 12 V battery, while large inverters use
a nominal DC bus voltage of 24 V, 48 V or higher.
For interactive inverters, the DC input voltage covers a wide
range (usually over 200 V) that permits the connection of
different voltage arrays operating under a wide temperature
range.
String sizing is used to match the array voltage and size to the inverter DC
input requirements.
The AC output voltage for all inverters is based on common
electrical system configurations and ANSI standards.
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Inverter Efficiency
Inverter efficiency varies with power level, input voltage and
temperature, among other factors.
Inverter efficiency is calculated by the AC power output divided
by the DC power input:
5700
0.95 95%
6000
where
= inverter efficiency
= AC power ouput (W)
= DC power input (W)
AC
inv
DC
inv
AC
DC
P
P
P
P
η
η
= = = =
AC Output:
5700 W
DC Input:
6000 W
Losses (Heat):
300 W
Inverter
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Inverter Efficiency
Inverter efficiency testing is conducted over a range of operating
voltages and power levels.
California Energy Commission
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Maximum Power Point Tracking
All interactive inverters employ maximum power point tracking
(MPPT) functions to extract maximum output from PV arrays.
Some inverters use MPPT at the source circuit or subarray level to
maximize array output.
MPPT is not usually incorporated in battery-based inverters,
although some charge controllers provide MPPT functions.
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Positive or Negative Grounding
Most interactive inverters allow configurations for grounding
either the positive or negative pole of the PV array.
Performance enhancements are achieved with certain PV modules using
a ground reference (SunPower).
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Grounded vs. Ungrounded Arrays
The grounding method for PV arrays affects the design of
inverter switching, as well as overcurrent protection and fault
detection for the system.
All U.S. inverters prior to 2010 use a grounded DC current-
carrying conductor from the array (positive or negative).
Ungrounded PV arrays are permitted by the NEC, and can help
facilitate fault detection within the array. Special requirements
apply to these inverters and systems.
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Bipolar Inverters
Bipolar inverters use two monopole PV subarrays for DC input,
with a positive and negative pole, and a center tap ground.
1200 VDC maximum voltage to inverter bus.
+600 VDC and -600 VDC PV output circuits referenced to ground.
Conductors and equipment need only be rated for 600 V if the PV output
circuits for each monopole arrays are run in separate conduit.
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SMA America
Interactive PV inverters from 700W to 500 kW
Stand-alone inverters 5 kW
www.sma-america.com
SMA America Family of Inverters
SMA
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Sunny Boy 2000HFUS /
2500HFUS / 3000HFUS
Residential string inverter
2-3 kW AC output
Integrated DC disconnect
Positive or negative ground
Indoor and outdoor rated
High-frequency, lightweight
10 year standard warranty
SMA
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Sunny Boy 2000HFUS /
2500HFUS / 3000HFUS
SMA
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Sunny Boy 2000HFUS /
2500HFUS / 3000HFUS
SMA
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SMA Sunny Boy and
Sunny Tower
3 to 8 kW single-phase string
inverters.
Integrated load-break rated DC
disconnect with fused combiner.
Tower configuration allows 6
inverters to connected to 3-phase
systems.
SMA
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SMA Sunny Boy 6000US
Configurations and Label
Locations and configuration for
GFID fuse and array grounding.
Listed interactive inverter
AC power, voltage
and current ratings
DC voltage and
current ratings
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SMA Sunny Boy 6000US
Wiring Terminals
DC input terminals AC output terminals
GFID and grounding configuration
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SMA Sunny Boy 6000US
Internal Components
DC input
capacitors
Monitoring display
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Sunny Boy Specifications
5000 US / 6000 US / 7000 US
SMA
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Sunny Boy Specifications
5000 US / 6000 US / 7000 US
SMA
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Sunny Tower 36 / 45
SMA
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Sunny Tower 36 / 45
SMA
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SUNNY CENTRAL 250U /
500U
250 kW and 500 kW AC power
output.
97% weighted efficiency with
integrated isolation transformer
Graphical LCD interface
Optional combiner boxes
Install indoors or outdoors
SMA
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Sunny Central 250U / 500U
SMA
2012 Jim Dunlop Solar Inverters: 8 - 97
SUNNY CENTRAL 500HE-US
500 kW high-frequency design,
lower weight.
SMA
2012 Jim Dunlop Solar Inverters: 8 - 98
SUNNY CENTRAL 500HE-US
SMA
2012 Jim Dunlop Solar Inverters: 8 - 99
Satcon PowerGate Plus Inverters
30 kW to 1 MW inverters for
commercial, utility scale and
hybrid off-grid applications.
www.satcon.com
Satcon
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Utility-Scale Inverters
Satcon
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Fronius USA
Interactive PV inverters from 2-12 kW
IG Plus units have separable wiring compartment and inverter power
stage, includes internal DC diconnect and source circuit fuses.
High frequency, multi-stage design and smaller transformers yield low
weight, 95%+ efficiency
www.fronius.com
Fronius
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Fronius IG Plus
Input Data
Fronius
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Fronius IG Plus
Output Data
Fronius
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Fronius IG Plus
General Data
Fronius
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Sizing PV Arrays for
Interactive Inverters
Interactive inverters can usually handle PV array DC power input
levels 110-130% or more of the continuous AC output power
rating.
Inverters thermally limit array DC input and power tracking at high
temperatures and power levels.
Array voltage requirements are critical:
Voltage must be above the minimum inverter operating and MPPT voltage
during hottest operating conditions.
Voltage must not exceed 600 VDC or the maximum inverter operating
voltage during the coldest operating conditions.
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String Sizing Tools
Interactive inverter manufacturers offer online string sizing tools
to determine the appropriate PV module configurations for their
products.
Inverter specifications define the operating limits for PV array DC current,
voltage and power.
PV module specifications and site temperature extremes are used to
estimate the range of array voltage and power output for specific series
and parallel module configurations appropriate for the inverter.
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String Sizing
Voltage
Array voltage decreases with
increasing temperature
0°C
-25°C
25°C
-50°C
STC
DC Input Operating Range
Inverter MPPT Range
PV Array IV Curves at
Different Temperatures
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SMA String Sizing Software
SMA
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SMA String Sizing Software
SMA
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SMA String Sizing Software
Predicted Results
SMA
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SMA String Sizing Software
Predicted Results
SMA
2012 Jim Dunlop Solar Inverters: 8 - 112
SMA String Sizing Software
Predicted Results
4) Estimated Inverter Maximum Output Power vs. High Temperature (°C/°F)
SMA
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SMA String Sizing Software
Predicted Results
5) Estimated Inverter Maximum Output Power vs. Low Temperature (°C/°F)
SMA
2012 Jim Dunlop Solar Inverters: 8 - 114
SMA String Sizing Software
Predicted Results
6) Estimated PV Array Maximum Output Power vs. High Temperature (°C/°F)
SMA
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Monitoring and Communications
All interactive inverters included integral monitoring and
communications interfaces to record, display and retrieve key
operating and performance information, including:
DC input operating parameters (array voltage, current and power)
AC output parameters (grid voltage, current and power)
Energy production (daily and cumulative)
Fault conditions and error codes
Data and operating status may be indicated on inverter panel
and/or retrieved remotely through communications interfaces.
Additional sensors for temperatures and solar radiation may be added to
some inverters and aftermarket monitoring systems.
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SMA Inverter Monitoring
SMA
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String Inverter Manufacturers
Fronius USA:
IG Plus 3 to 12 kW
KACO new energy:
1.5 to 5 kW
Motech: PVMate
2.7 to 5.3 kW
Power One:
3 to 6kW
PV Powered:
1.1 to 5.2 kW
SMA America:
700W to 7 kW
Solectria Renewables:
1.8 to 5.3 kW
Xantrex Technology:
2.7 to 5 kW
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Large Inverter Manufacturers
Advanced Energy
Fronius
Ingeteam
Kaco new energy
Power-One
PV Powered
Satcon Technology
Schneider Electric
Siemens Industry
SMA Solar Technology
Solectria Renewables
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Summary
Inverters are used in PV systems to convert DC power from batteries or
PV arrays into AC power suitable for loads.
Different components and circuitry are used in various inverter designs.
Stand-alone inverters operate from batteries and supply AC power to
dedicated loads off-grid.
Interactive inverters operate from PV arrays and produce AC power to
interface with the utility system. Types of interactive inverters include
module-level, string, central, utility-scale and bimodal inverters.
Most inverters incorporate monitoring and communications functions to
record and display system operating parameters, fault conditions and
performance information.
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Questions and Discussion