Pnom ratio too high, and not allow for simulation

[garf]

Hi All,

I have a system where I use CSI 545W PV and Ginlong Solis-100K-5G inverter.

The Solis-100K-5G has 10 MPPT and 2 input per MPPT.

I wanted to configure the following string configuration in Pvsyst. In my sub-array #3, I have 2 x 22PV per string to one MPPT. So, each input of the MPPT has a 22PV per string.

By default, Pvsyst said the Pnom ratio of the MPPT is 2.42... And Pvsyst not allow for simulation.

In that case, can I use Power sharing to allocate more power to the said MPPT and make it pass for simulation?

Thanks in advance for advices.....

 

 

[dtarin]

The DC/AC ratio is very high, to the point that the inverter manufacturer may not warrant the product in a PV-only system. The maximum DC/AC ratio according to the datasheet is around 150%, or 1.5, which is fairly common. Is this a DC-coupled battery system?

Edited February 22, 2023 by dtarin

[dtarin]

After having a second look (and since I can't edit), use power sharing for sub arrays 2-5 and balance the DC/AC ratio across all inputs.

[garf]

6 hours ago, dtarin said:

The DC/AC ratio is very high, to the point that the inverter manufacturer may not warrant the product in a PV-only system. The maximum DC/AC ratio according to the datasheet is around 150%, or 1.5, which is fairly common. Is this a DC-coupled battery system?

Hi, thanks for your time reviewing. It is a grid tied system, no battery involved.

 

[garf]

6 hours ago, dtarin said:

After having a second look (and since I can't edit), use power sharing for sub arrays 2-5 and balance the DC/AC ratio across all inputs.

I see, so as long as I balance the DC/AC across the input to say below 1.5, it is acceptable right? thanks again 

[André Mermoud]

One of your strings is 550W * 22 = 12.1 kW.  One inverter input allows  100 kW / 10 = 10 kW "nominal".  Therefore putting 2 strings on one MPPT input leads to a PNom ratio = 2.42. which is not reasonable.

In a multi-MPPT inverter like this one, you can indeed charge a MPPT more than the other ones (i.e. define some  MPPT inputs with 1 string, and some MPPT with 2 strings). But not with such an individual PNom ratio (as dtarin said, 1.5 or a bit more).

However if the difference is too high: this will probably not be allowed by the manufacturer, and you will have high current losses in the more charged MPPT.

See the help  "Project design > Grid-connected system definition > Multi-MPPT inverters > String inverters, current limiting"

 

 

 

 

 

 

 

[garf]

15 hours ago, André Mermoud said:

One of your strings is 550W * 22 = 12.1 kW.  One inverter input allows  100 kW / 10 = 10 kW "nominal".  Therefore putting 2 strings on one MPPT input leads to a PNom ratio = 2.42. which is not reasonable.

In a multi-MPPT inverter like this one, you can indeed charge a MPPT more than the other ones (i.e. define some  MPPT inputs with 1 string, and some MPPT with 2 strings). But not with such an individual PNom ratio (as dtarin said, 1.5 or a bit more).

However if the difference is too high: this will probably not be allowed by the manufacturer, and you will have high current losses in the more charged MPPT.

See the help  "Project design > Grid-connected system definition > Multi-MPPT inverters > String inverters, current limiting"

 

 

 

 

 

 

 

Hi, thanks for sharing your view.

How about if I balance the Power over the MPPT like the following, end up each MPPT is about 1.39 DC:AC?

Some of the MPPT power go up to 17.39kW though.... 

Appreciate your view on this... thanks again

 

[dtarin]

I don't know this inverter specifically, but with other string inverters I have worked with, the inputs can be 'jumpered', so that power is shared across all inputs. Power sharing emulates this behavior. Select "use the sharing...." and select all four sub-arrays onto one Inverter config, then press All PNom ratios identical. Since it looks like you have done that (all have Pnom ratio the same), you should be good. 

Edited February 24, 2023 by dtarin

[garf]

On 2/24/2023 at 11:51 PM, dtarin said:

I don't know this inverter specifically, but with other string inverters I have worked with, the inputs can be 'jumpered', so that power is shared across all inputs. Power sharing emulates this behavior. Select "use the sharing...." and select all four sub-arrays onto one Inverter config, then press All PNom ratios identical. Since it looks like you have done that (all have Pnom ratio the same), you should be good. 

ok, noted.. thanks for sharing ...