Parallel String Connection In SG250HX, -How to Simulate Pvsyst On Parallel String Connection

[Piyush Shah]

Hi,

I have one 200KW inverter with 12 MPPT and a load limit of 200KW at the inverter level. The DC capacity is 311.04 kWp, and I have a total of 16 strings, with 36 modules per string, each rated at 540Wp.

In both cases, when running PVsyst:

Case 1: If I run PVsyst on one inverter with 16 strings, the result is PR (Performance Ratio).

Case 2: If I run PVsyst with 12 MPPTs and 16 strings, the result for PR differs. (4 MPPTs with 2 strings and 8 MPPTs with 1 string)

In both cases, PR varies , and inverter losses over nominal inverter power loss are high in case 2.

 

which case is correct

 

[Linda Thoren]

Dear Pizush Shah,

The PR will be lower with higher inverter losses. In Case 2, if you have created a sub-array for each MPPT, 4 sub-arrays with two strings and 8 subarrays with 1 string (or alternatively a first sub-array with 4 MPPT and 8 strings and a second sub-array with 8 MPPT and 8 strings) you correctly have a number of strings that is a multiple of the the MPPTs used. By activating the Power sharing between the sub-arrays this should lead to similar results as in Case 1. The green led will be activated if Power sharing has been correctly defined

Regards

[Piyush Shah]

But in this case, due to power sharing, inverter losses are lower at the site."
But at the actual site, due to a 200 kW load curtailment, the higher-loading MPPT is performing poorly, leading to an overall increase in inverter losses

 

 

Inverter -1 Inverter.pdf Inverter -1 Power Sharing.pdf

[Linda Thoren]

Power sharing ensures that the power generated by each MPPT controller is efficiently distributed across the different strings or groups of panels. This prevents one string from overloading while others underperform, maintaining overall system balance and efficiency. In your case, by not ticking the alternative "Auto-equal. Pnom" you are strongly overloading the first 3 MPPT, resulting in a Pnom ratio of 2.35, and a quite low Pnom ratio of 1.18 for the remaining 9. The Pnom ratio being the ratio between the installed power of the solar panels and the inverter (usually around 1.25). In your case without activating the MPPT-feature, it is equally distributed over the MPPTs with a Pnom ratio of 1.47