SolarEdge Architecture

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SolarEdge Architecture

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See also Power Optimizers for generalities about these devices.

The SolarEdge distributed architecture is based on a unique system design approach, characterized by a distributed DC-DC power optimizer for each PV module (or group of PV modules). These optimizers, with a current-driven output, are connected in series as strings, which are then connected in parallel to the input of a special (proprietary) inverter.

Each power optimizer can manage 1 to 4 PV modules, and performs the MPP tracking at the input module (or group of modules) level.

The SolarEdge optimizers work in Buck-Boost mode.

The specificity of the SolarEdge inverters is that the voltage of the full optimizers string is fixed  (usually 350V or 700V for most inverters), so that the current of the whole string  (i.e. each optimizer output) is imposed according to the available PV power at Pmpp of each input module.

During the simulation, the efficiency of each optimizer is evaluated. It depends on the Current boost ratio (the longer optimizer string, the lower efficiency).    

Operating at a fixed voltage means that the Power Optimizers in a string operate completely independently one from the other, so that at a given time the module productions may be different without any effect on the system (shadings, mismatch, different orientations, etc).

In PVsyst this requires a very special procedure for the elaboration and sizing of the system.



The main relevant parameters of a SolarEdge Power Optimizers are:

-Input parameters VmppMin, VmppMax and VabsMax, which determine the possible number of PV modules to be connected at the input, in the same way as for any MPPT inverter input.
-POptMax: the maximum power admissible on the device.  As a contrary of usual PVsyst practice (i.e. nominal Pnom of PV modules), the Maximum power to be considered for SolarEdge devices is the Power obtained  by clear sky conditions.  
-VOptOutMax : the maximum output voltage of the Power Optimizer  (for example 60V).
-VOptOutMin : the minimum output voltage of the Power Optimizer (for example 5V).
-IOptOutMax . the maximum output current of the Power Optimizer.

The main parameters used for the sizing of the inverter are:

-PmaxAC: The nominal output power to the grid.
-PMaxDC: the corresponding power at the DC input, i.e.   PmaxAC / efficiency at PMax
-VinvNom: fixed input operating voltage
-IDCMax:  corresponding to the maximum power  (= PMaxDC / VinvNom).


The sizing rules for SolarEdge devices are extremely complex:

- only specific optimizers are compatible with specific inverters.

- the minimum and maximum number of optimizers in a string is defined for each association  Optimizer-Inverter.

- the maximum number is also limited by a maximum admissible power for one string.

- each inverter may be undersized by a Pnom Ratio specified for each model  (usually 1.35, some models with 1.55).

These complex rules lead to define the SolarEdge systems with a very new concept in PVsyst, i.e. create a list of "physical" inverters, and associate different strings to each of them.  See the "SolarEdge Procedure"  page for further details.

Power Optimizer parameters definition

The available Power Optimizers and their parameters may be displayed in the SolarEdge optimizer definition (specialized optimizer parameters dialog). As the Power Optimizer are proprietary devices of SolarEdge, their parameters are not directly modifiable, but only defined in the original database of PVsyst.

System sizing

As with any usual system, you are advised to start by specifying the required power for your subfield (or the available area). After that you have to choose a PV module.

When choosing a SolarEdge optimizer, the system sizing dialog will change to a suited dialog for the SolarEdge architecture, and predefine the number of required optimizers for your system size.

You have first to choose the Power Optimizer to be used in your system (in the PV module group).

Then in the Array design part, please define the Power Optimizer input configuration, i.e. the number of PV modules connected to each Power Optimizer (according to number of available inputs).  

Then you define the inverter input:

-The number of Power Optimizers in Series. The limits described above are shown on the right of the edit box. The nominal power corresponding to a whole string is shown, as well as the part of the inverter capacity (in percent).

This very important information indicates how many identical strings you can connect on one inverter. For example if more that 50%, only one string of that length can be connected to each inverter.

-The number of Strings in Parallel. When one only string is allowed per inverter, this will be limited to the number of inverters. Below 50% capacity, this will be 2 times this number, or more…

You are of course advised to use the  "Show Sizing" tool for visually checking the sizing of this sub-field.

Systems with different strings

When you have strings with different lengths, you should define different sub-arrays, one for each length to be defined.

In each sub-array, you have to define a number of strings, and a number of concerned inverters. This means the number of physical inverters which will receive one or more of the strings defined in this sub-array.

The attribution of different strings to different physical inverters is done in a specific dialog to be open with the button "Strings configuration". This dialog is described in the previous page SolarEdge Procedure.


With distributed SolarEdge architecture:

-there are no mismatch losses,
-the optimizer efficiency is now evaluated in detail, using modifications due to the Current boost ratio into account.  
-the electrical effect has to be evaluated using the "Module Layout" tool, which is adapted for SolarEdge optimizers.
-the shadings option "according to module strings", as usually used with rectangle-strings corresponding to the modules of one optimizer input, is not really suited. It will give under-evaluated Electrical Shading loss.