J Lanka - SolarEdge provides next generation solar power harvesting and monitoring solutions that effectively remove all known system constraints across the photovoltaic energy space. Our Smart DC ASIC technology and active electronics enable increased production of clean, grid-ready energy at a lower cost. Traditional photovoltaic installations suffer from a broad range of limitations that prevent them from reaching their full potential. Module mismatch and partial shading prevent systems from achieving their optimum. System design is made complex due to numerous constraints, such as the inability to leverage full roof real estate, to combine strings of different lengths, or to easily address differing roof facets. Traditional systems lack monitoring and analysis capabilities, as well as critical safety features. The systems can pose risks to workers installing or maintaining the system, as well as to firefighters dealing with fires in the vicinity of a PV installation.

1. The difference between
The SolarEdge distributed power harvesting system
And
Conventional Systems
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2. The typical specifications of a solar panel
Output Current (A) Isc – the output current of the panel when
output terminals are short circuited
Maximum power point Voc – The voltage at the output terminals
Isc without any load connected to the panel
Impp Maximum power point is the point which
gives the maximum value for the V x I
To harvest power from the solar panel
requires to monitor where this point is.
This process is called Maximum Power
Point Tracking or MPPT
Voc
The values of V and I at the maximum
Vmpp power point is referred to as Vmpp and
Output Voltage (V) Impp respectively.

3. The variation of maximum power point of a solar panel according to
solar irradiation
Solar irradiation level
Maximum power point at
Pout = 150W corresponding solar
irradiation level
Pout = 128W
1000Wm-2 is the sun light
Pout = 96W level at noon under clear sky
or bright day light
Pout = 66W
The panel output voltage is
Pout = 35W
almost constant, but the
output current significantly
varies with solar irradiation
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4. The variation of maximum power point between similar brand and
power rated solar panels for the same level of solar irradiation
All the three panels are
manufactured by the same
manufacturer, in the same
production line. But the power
output is not similar and
unmatched.
Also the maximum power
point is not same, and exists a
considerable variation among
each other. That is at the same
voltage, the output current is
different
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5. The panel layout of a typical solar power generation system
String of PV panels
+ - + - + - + -
+ - + - + - + -
Inverter Typical string may have up to 20 panels
per string and two or three such strings
DC
are connected in parallel to form the DC
230 Vac supply to the inverter.
AC
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6. The problems and disadvantages of a typical solar power generation
system
1.The panel mismatch
Averaged String current ( )
When several modules are connected in series,
each one has a slightly different MPP current. The
series connection does not allow the optimal MPP
current to be drawn from each module. The
Output Current (A)
inverter will select the current which gives the
average peak power point of the string or array.
This peak power is always less than the theoretical
sum of the individual peak power points of every
module.
This is referred to as mismatch loss. In standard
residential and commercial PV installations, it can
be as high as 5% !
Output Voltage (V)
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7. The problems and disadvantages of a typical solar power generation
system 2. Partial shading
Shading on any part of the array will reduce its output,
but this reduction will vary in magnitude depending on
the electrical configuration of the array. Clearly, the
output of any shaded cell or module will be lowered
according to the reduction of light intensity falling on it.
However, since this shaded cell or panel is electrically
connected to other unshaded cells and modules, their
performance may also be lessened since this is
essentially a mismatch situation.
Partial shading of crystalline solar modules will result in
dramatic reduction of solar module output. One
completely shaded cell can reduce a
solar module’s output by 40% to 95%.
In residential systems, partial shading losses are
estimated to contribute between 5% to 25% annual
power losses
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8. The problems and disadvantages of a typical solar power generation
system
3. Inefficient MPPT algorithms
The MPPT algorithms must be able to efficiently track the power point variation as the solar irradiation
changes time to time. If it is not, there will be tremendous amount of loss in the harvestable power.
4. System feedback and trouble shooting
A solar installation will cost a considerable amount of money. But the problem is, There is no way to find out
individual panel performance except entire systems performance. This becomes tragic since a malfunctioned
panel can be hidden inside the system, while the clouds being the guilty party!
5. Retrofit and long term fault tolerance
For conventional solar installations, it requires all the solar panels to be in same ratings. That is no way to
connect a different panel. The solar panels comes with a 20 years or more warranty period and the
technology behind the panels keeps developing each day like mobile phones. So after 10 years how can
some one can find a panel that is exactly similar to the ones that was installed 10 years ago! The
conventional systems becomes a dead end in this case.
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9. The problems and disadvantages of a typical solar power generation
system
6. System safety
When solar panels are installing it is very difficult to cover from the sun. There for the series connected solar
panel string is always live. Even a series connected three panels (36V) produce enough power to electrocute
a person if accidently touched.
Also in case of a fire, there is no way to shut down the strings. In such a cases these Dc power lines can be
short circuited and become another fire causing factor.
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10. Conclusion
We described the structure of PV systems and several drawbacks and disadvantages in the
way these systems are designed and built. Though previous works focused on improving
different aspects of photovoltaic systems, no single holistic approach was presented that
could solve many of the current problems present in PV installations.
Solar Edge Technologies distributed power harvesting system is the only power harvesting
system and architecture that offers a full, robust solution that harvests up to 25% more energy
and resolves the issues described in this paper.
The next sections describe how the SolarEdge distributed power harvesting system handle all
these issues.
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11. Back to some basics….
Power = Voltage x Current
That is a 100W can be expressed as,
Power (W) Voltage (V) Current(I)
100 10 10
100 20 5
100 25 4
100 50 2
The idea here is Power Conversion. To do this a special device known as DC-
DC converter has to be used. It does the same thing above. That is we can
input it a 100W (20V x 5A) and take a 100W of power at 50V x 2A. This also
can be done in the opposite way.
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12. The SolarEdge System
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13. The SolarEdge System…How this works
The method of connection
1. Each panel must be connected to a power optimizer
2. These power optimizers are then connected in series to form the strings
3. There must be at least 8 such power optimizers per string
The method of functionality
1. As the sun rises the panels start power production and wakes the power optimizers
2. The power optimizers check how much POWER can be take from the panel they connected
3. Then all the power optimizers send these details to the inverter
4. The inverter process these data and commands all of them to start power production. The output
voltage of the power optimizers will be changed so as to maintain a constant current and also to
response shading conditions. This will be explained in detail in coming sections.
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14. The SolarEdge System VS All known Mismatches
As we said earlier, solar panels are not matched even they are power
rating is similar and from same brand
The problems and losses due to the series connected such panels are were
also discussed in greater detail.
Since in SolarEdge system, the actual string is made of series connected
power optimizers and the panels are connected to the power
optimizers.
That is the panels are buffered by the power optimizers from the DC bus.
The power optimizer harvest energy from the panel and supply it to
the DC bus.
There for not only mismatched panels, but even different panels can be
used for the installation.
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15. The SolarEdge System VS Shadings
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16. The SolarEdge System VS Mixed panels
1. The solar panels are connected to the power optimizers
2. There for the panels and the string are independent from each
other.
3. So as the input of the power optimizer any panel can be connected.
The power optimizer converts what ever the available power from
the panels to the required level by the inverter as explained earlier.
4. This is the only system that can be used with mixed panel types.
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17. The SolarEdge System VS Monitoring and Safety
1. This is the only system that comes with a WEB based monitoring
facility as a standard feature.
2. It monitors entire system performance to each panels performance
in every 30 minutes and updates the web portal provided by the
manufacturer.
3. So isolating a fault is just a few minutes job and locating it in the
installation is even simpler and can be done even from the office.
There for only the required panel can be removed without shutting
down the system.
4. Also until inverter commands the power optimizers does not
output power and it will output only 1V. This very much helpful
since the number of panels installed is equal to the output voltage.
For example 15 series connected panels means 15V. Any loosely
connected panel or polarity changed panel can be identified easily.
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18. The SolarEdge System VS Power Point Tracking
1. A conventional system can have maximum of 2 maximum power
point tracking's. This too is not the optimum and it is a averaged
one as explained earlier.
2. But in solaredge system. The power point tracking is implemented
in each power optimizer. There for every panel has a dedicated
maximum power point tracking implemented for its own.
3. The end result is solaredge system has minimum of 8 maximum
power point tracking and increases with addition of every power
optimizer to the system.
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