SolarEdge inverter efficiency as a function of string configuration

[smeredith]

I have noticed when modeling systems using SolarEdge architecture that the SolarEdge inverter efficiency (and overall, the system energy) doesn't change when the strings are configured differently - as long as the total number of strings of each string length remains the same.

As an example, compare the two variants below.

Simulation A:

Subarrays:

• Subarray 1: SE 33.3k inverter with 24 modules per string, 45 strings in parallel
• Subarray 2: SE 33.3k inverter with 22 modules per string, 45 strings in parallel

String configuration:

• 10x inverters with 3 strings of 24 mods/string and 0 strings of 22 mods/string
• 10x inverters with 0 strings of 24 mods/string and 3 strings of 22 mods/string
• 5x inverters with 2 strings of 24 mods/string and 1 string of 22 mods/string
• 5x inverters with 1 string of 24 mods/string and 2 strings of 22 mods/string

Results:

• Inverter efficiency loss: -1.77%
• Yield: 1944.584 MWh

 

Simulation B:

Subarrays:

• Subarray 1: SE 33.3k inverter with 24 modules per string, 45 strings in parallel
• Subarray 2: SE 33.3k inverter with 22 modules per string, 45 strings in parallel

String configuration:

• 15x inverters with 2 strings of 24 mods/string and 1 string of 22 mods/string
• 15x inverters with 1 string of 24 mods/string and 2 strings of 22 mods/string

Results:

• Inverter efficiency loss: -1.77%
• Yield: 1944.584 MWh

 

Although both simulations have a total of 45 strings of 24 mods/string and 45 strings of 22 mods/string, the string configurations are quite different.  Because the inverter loading is different, I would expect the overall efficiency loss to be different.  Yet when I run the simulations, I see that the efficiency loss and yields are identical.

Is this intended behavior?  If so, why?