Microinverter

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saman1368
Microinverter

Hi
I am modeling simple residential building with a PV system, I would like to compare the result of using micro-inverter and string inverter under the same shading condition. For string inverter, I've used 3D shading calculator (12 module per string, 1 string parallel, and 1 inverter) however for microinverter 1 module per string,12 string in parallel and 12 inverters, I would like to know is there anyway that I can use 3D shade calculator to calculate the shading for my system, if yes how,will it take into account the presence of micro-inverter or not.

Paul Gilman

Hello,

In short, yes. However, SAM's 3D shade calculator only works with up to 8 strings per subarray. To illustrate this, I added a third attachment to your original post. It is a SAM file with several cases described below:

Original

This is the original case from your file.

Microinverters

In this case, I modified your original case as follows:

  • Change the inverter to one with a capacity of 250 Wac so I could compare it to a system with a 2000 Wac string inverter
  • Change the system design to a system with 1 module per string, 8 strings in parallel, and 8 inverters because SAM's 3D shade model cannot calculate shade losses for a system with more than 8 strings.
  • In the 3D shade scene, replace the single active surface with 8 active surfaces, each representing a single module wired as a separate string (Subarray 1 consists of 8 strings of one module each).
  • In the shade window, enable partial shading and set the number of strings to 8.
  • On the Losses page, set the module mismatch loss to 0, assuming that the microinverter system would not experience those losses

String Inverter

  • Use an inverter rated at 2000 Wac with a maximum MPPT voltage rating above the subarray open circuit voltage rating (appropriate for initial sizing)
  • On the System Design page, set modules per string to 8, strings in parallel to 1, and number of inverters to 1. This makes the system design capacities comparable to the microinverters case.
  • In the 3D shade scene, a single active surface represents the entire array.
  • In the shade window, enable partial shading and set the number of strings to 1.

Microinverter - One Module

This example uses a single module with one string inverter and partial shading enabled to show that SAM calculates partial shading for a single module in addition to doing so for a subarray of several modules.

Microinverter - One Module No Partial Shading

In this case, I disabled partial shading in the Shade window to compare with the previous case. When partial shading is disabled, SAM models external shading as a reduction in POA irradiance, and does not account for the effect of diodes on the module's DC output.

Please see the notes I wrote in the case (you'll see yellow post-it note icons in the navigation menu indicating where the notes are) for additional details.

Best regards,
Paul.

saman1368

Thanks a lot Paul
How can i download your attachment , i cant find it

saman1368

Thanks for clarification but i cant find the attachment

Paul Gilman

Sorry -- it should now be attached to your original post above.

Thanks,
Paul.

saman1368

Thank you so much Paul , It helped a lot

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