Multiple inverter panel configurations

Tuesday, September 7, 2021
Training
by
Veli Markovic

Where we left off from last time

In part 1 we looked at how to create a spreadsheet for larger commercial solar projects in regards to panel and inverter configurations.

In part 2 we examined how to extract the various data; inverter and panel specs and in this final presentation we put it all together with a case study of a system that uses 4 x inverters and 2 x panel types with a system size aim of just under 320 kW.

Let’s get stuck into it!

Step 1: select your inverters and enter details




  • Inverter option number: 1
  • Inverter brand: Huawei
  • Model number: SunT100
  • Capacity in kW: 100
  • No. of MPPT: 6
  • No.of inputs per tracker: 2
  • Max. Input Voltage: 1500
  • Rated input voltage: 1080
  • Max. Current per MPPT: 22
  • Max. Isc  per MPPT: 33
  • MPPT Op Voltage Range: 600 -1500
  • Rated AC Active Power: 100,000


Step 2: select your panels and enter details


  • Solar panel option number: 1
  • Solar panel brand: ACME 1
  • Solar panel wattage: 445
  • Voc: 48.9
  • VocMax: 53.52
  • VocMax buffer: 1
  • VocMax with buffer: 53.52105
  • Vmpp: 40.9
  • Isc: 11.6
  • Impp: 10.89
  • Max series fuse ratings: 20
  • Temperature Coefficient (Vmax): 0.27%
  • Record low temperature of location, user input: -10
  • STC temperature of panel: 25.00
  • Vmpp x Impp: 445.401


Step 3: create formula to measure VocMax

Step 4: create formula to measure VocMax with buffer

The VocMax with buffer calculation takes into account the VocMax maths and then multiplies by the buffer which in this case is 1.

Step 5: first inverter, option 1, panel option 1



You can create a formula for the signage based on inverter number, MPPT number and string input number.

In addition there are formulas to calculate the VocMax of the string, is the rated input voltage exceeded etc. For more details see part 1 and 2.

Do the same for inverter 2,3 and 4


In this case the DC/Ac voltage has been exceeded so need to adjust

That’s better!

Step 6: Create the formulas for summary of inverter 1

  • ="Inverter no."&$W47 =F48
  • Inverter option no. =D48
  • Brand =XLOOKUP(D48,B21:K21,B22:K23)
  • Model =XLOOKUP(D48,B21:K21,B22:K23)
  • Capacity        =XLOOKUP(W48,B21:K21,B32:K32)
  • amount of solar in kW =S60/1000
  • DC/AC ratio =S60/W51
  • String with highest VocMax =MAX(M48:M59)
  • Total current in Amps =SUMIF(L48:L59,">0",Q48:Q59)
  • Panel brand =XLOOKUP(J48,B2:K2,B3:K3)
  • Wattage        =S60/SUM(L48:L59)
  • Number of panels =SUM(L48:L59)
  • Number of strings =COUNTIF(L48:L59,">0")

And you end up with a nice summarised table ( see below)




Perform the same procedure for all the inverter and panel configurations, in this there are 4.

Effectively the information extracted can be used for other things as BOM list or similar in addition to its primary purpose of inverter panel design for large commercial solar systems

What now?

We have collected all the relevant information for each of the inverter panel combinations and now we need to put together a summary of the summaries. . . . 

Step 7: List the inverters used

Components

  • Inverter no.1
  • Inverter no.2
  • Inverter no.3
  • Inverter no.4
  • ="Panel "&RIGHT($Z48,4)
  • ="Panel "&RIGHT($Z49,4)
  • ="Panel "&RIGHT($Z50,4)
  • ="Panel "&RIGHT($Z51,4)


In regards to the panels they reference the inverters used and extract the last 4 characters. For example Inverter no.1 matches with panel no.1 etc

Step 8: Find the inverter and panel brands

Model                                                               How many

=OFFSET(XLOOKUP($Z48,$V$47:$V$113,$W$47:$W$113),3,0) 1

=OFFSET(XLOOKUP($Z49,$V$47:$V$113,$W$47:$W$113),3,0) 1

=OFFSET(XLOOKUP($Z50,$V$47:$V$113,$W$47:$W$113),3,0) 1

=OFFSET(XLOOKUP($Z51,$V$47:$V$113,$W$47:$W$113),3,0) 1

=OFFSET(XLOOKUP($Z48,$V$47:$V$113,$W$47:$W$113),10,0) =OFFSET(XLOOKUP($Z48,$V$47:$V$113,$W$47:$W$113),11,0)

=OFFSET(XLOOKUP($Z49,$V$47:$V$113,$W$47:$W$113),10,0) =OFFSET(XLOOKUP($Z49,$V$47:$V$113,$W$47:$W$113),11,0)

=OFFSET(XLOOKUP($Z50,$V$47:$V$113,$W$47:$W$113),10,0) =OFFSET(XLOOKUP($Z50,$V$47:$V$113,$W$47:$W$113),11,0)

=OFFSET(XLOOKUP($Z51,$V$47:$V$113,$W$47:$W$113),10,0) =OFFSET(XLOOKUP($Z51,$V$47:$V$113,$W$47:$W$113),11,0)


There was no formula to determine how many inverters as there are only 4 but the formulas were used to determine the different amount of panels used.

Step 9: Finished summary of inverters and panels

What more can we do? 

Number of boxes needed

A bit extra

What is the combined currents of all the panel strings



What is the highest VocMax of any string on the project?

Conclusion

When commercial solar projects become large and more complex you really need to start utilising tools that can reduce the amount of time spent on tasks such as project design and the creation of a bill of materials. These presentations have used Excel and some functions such as XLOOKUP may be unavailable in other programs but everything shown here can be achieved with other functions.

The most important thing is to use your time wisely and efficiently and having certain tools at your disposal can help a lot.

Good luck on your next project.

If you’d like to see more of what Greenwood Solutions get up to in the real world of renewable energy, solar, battery storage and grid protection check out the following pages:

https://www.greenwoodsolutions.com.au/industry 

https://www.greenwoodsolutions.com.au/commercial

https://www.greenwoodsolutions.com.au/commercial/customer-stories

https://www.greenwoodsolutions.com.au/news


About the author

Veli Markovic

CEC Designer
Veli has nearly two decades of experience in the renewable industry. He is passionate about providing people with valuable education and is highly regarded throughout the industry as an educator and operator.
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