Severe Bug in the software

[Aboud]

Dear All,

 

Let's imagine the following Scenario

 

PV installed Capacity 40KWp

Inverter size 80kW

choosing this size for the installed DC capacity prohibits the program from finishing the simulation although the MPPT voltage and current ranges are within the allowed limit when choosing array connection!

 

if the inverter size >>>> PV installed capacity, it shouldn't stop the program finishing the simulation. Me and the customer are aware that the Inverter size is almost double PV capacity, the reason for choosing the inverter size is there will future PV expansion up to 100kWp (DC)

 

My comment is:

PV sol should fix this bug and let the customer know the alert message without stopping the simulation. if not, this reduces the program reliability as Many customers choose a bigger inverter size for future PV system expansion.

 

Many thanks in advance!

 

[developer_fw]

Hello Aboud,

I am not quite sure what you mean, since PV*SOL is able to do exactly that.

The following example shows a configuration with ~40kWp and a sizing factor of 51.2%:

Even without enforcing it, the simulation finishes, albeit the warning as a user info.

 

When doubling the number of modules configured with the same inverter the warning disappears, and of course the simulation finishes without a problem:

 

I'd really like to help you out, so could you be more specific about when you do run into a problem? Can you give an example of the point at which the error you are talking about occurs? Can you send an example project?

Kind regards,
Frederik

[Aboud]

Hi Frederik,

 

Many thanks for your interest and your description.

 

I have tried the same approach you mentioned and the simulation is finished Even if using extreme values.

Kindly check the example below (sizing factor=51.7) 

Total installed DC =41.4 kWp / Inverter capacity 80kWac.

 

I have 2 queries

1. When inverter size > PV system size as shown above, Why the software prohibits the proper MPPT configuration and let the user to configure it manually?!!

the inverter can definitely host the PV system and you can clearly notice the 'Auto configuration' is deactivated!! (regardless the X sign near the inverters whose sizes?PV system which i think it should replaced by warning symbol)

 

2. The inverter model above has 4 MPPTs, each can be connected to 4 strings. I was trying to apply the following configuration

my question is how to configure each string in MPPT2 separately as shown above and therefore 72 Modules can be connected to MPPT2. I understand String 3 with 18 modules could lead to 'Mismatching'. However, this is not serious and the designer should decide to proceed forward. How to split MPPT strings so that I can apply the configuration above?

 

Once again, Many thanks for your valuable reply! Many thanks in advance!

 

[developer_fw]

Hi Aboud,

to the first part before your question:

As you can see in your first screenshot next to MPP1 the configuration check informs you about possible issues.

In your second screenshot, you are on the level of the inverter, as you can see by the marked entry in the treeview on the left.

When clicking onto the entry below (MPP1), you get detailed info about the values for the selected MPPT. In this case, you did connect too many modules which leads to a too high Open Circuit Voltage for your inverter. Be extra careful with voltage limitations! It is essential to comply with manufacturers limitations since this can lead to damage at the inverter!

 

On 8/17/2022 at 4:25 PM, Aboud said:

1. When inverter size > PV system size as shown above, Why the software prohibits the proper MPPT configuration and let the user to configure it manually?!!

For being able to use the automatic configuration, you have to select inverters from the database, which should be used for the algorithm. By limiting the number of inverters, the number of combinations is less and the calculation performs more quickly.

By clicking Inverter-Selection the Inverter database list opens and you are asked to select 1+n Inverters which should be used. In your case, I assume you maybe did select the Inverter; unfortunately our algorithm which identifies the suitability does not have parameter constraints like e.g. the maximum number of MPPTs you want to use, if you do want to put strings in parallel etc...
We are thinking of implementing something like this.

 

On 8/17/2022 at 4:25 PM, Aboud said:

2. The inverter model above has 4 MPPTs, each can be connected to 4 strings. I was trying to apply the following configuration

The 27 modules in row per string yield a voltage above the allowed maximum voltage of the modules:

The maximum number in this case is 24 modules, independent of the maximum input voltage of your inverter.

So in this case you have to either use a different kind of module which allows a system voltage of 1100V or not exceed the 1000V.

 

While writing this answer I stumbled upon the datasheet of the inverter and I guess there must be something wrong with the database entry!
https://www.rayleigh.com/media/uploads/RI_Data_Sheet_RI-EnergyFlow-3P-Series-80_W_24_06_22.pdf

The maximum input current sums up to 158, so the 44A and 35A maximum input currents lead to an estimation of 33kW and 26kW maximum input power of the two different MPPT types. By copying the database entry and changing those values you get a proper configuration check.

I also informed our database team so they get back to Rayleigh Instruments Ltd. for cross checking my assumptions.

I hope this clears several mysterious issues you did ran into!

Kind regards,
Frederik

[Aboud]

Dear Frederik,

 

Many thanks for your quick response and detailed illustration.

1. I think the 'automatic configuration' only works when the software recognize the convenient inverter size relative to DC installed capacity (or up to specific sizing factor). I have already selected the inverter (video attached). However, 'automatic configuration' is still inactive. To be fair it is not a big problem because the software allows the simulation although a significant 'sizing factor' is introduced. According to my modest opinion, PVsol algorithm should activate an 'automatic configuration' regardless the 'sizing factor' and suggest the maximum modules per MPPT as normal (when inverter size is convenient). Also, as long as 'Crossing out' sign is introduced next to the inverter, automatic configuration won't work.

 

2. According to PV module specs, Voc=36.8V, Vmp=29.5V and Maximum system voltage =1000V 

 

Using Voc value (worst case scenario), 27 modules will generate 27*36.8= 993.6V < (maximum sys voltage).  However, I understand this value is too close to 1000V but the inverter model used (as attached above) can handle up to 1100V per MPPT and therefore the simulation could proceed regardless the warning message below:

 

To be fair I am 100% satisfied with the software but I think some minor but I think some minor modifications with the algorithm will lead to outstanding performance.

 

Many thanks in advance Frederik, You did a significant effort!!!!

 

[developer_fw]

Hello Aboud,

On 8/19/2022 at 2:12 PM, Aboud said:

1. I think the 'automatic configuration' only works when the software recognize the convenient inverter size relative to DC installed capacity (or up to specific sizing factor). I have already selected the inverter (video attached). However, 'automatic configuration' is still inactive.

The Configuration Limits are respected for the Automatic Configuration, so to activate the automatic configuration you have to change the configuration limits first.

After changing the sizing factor:

Select Configuration gets available:

You are right though that there is no option to set MPP usage to max for example.

 

On 8/19/2022 at 2:12 PM, Aboud said:

2. According to PV module specs, Voc=36.8V, Vmp=29.5V and Maximum system voltage =1000V

The maximum system voltage is valid for the modules, be extra careful to not exceed it for not breaking any components with electric arcs. This maximum voltage is not the same as the maximum input voltage of the inverter. Even if the inverter allows for 1100V, your modules might not survive higher voltages. Of course this depends and it might work out nicely. In case there is an accident, no insurance company will be paying for the damage.

 

On 8/19/2022 at 2:12 PM, Aboud said:

Using Voc value (worst case scenario), 27 modules will generate 27*36.8= 993.6V < (maximum sys voltage).

The test conditions in PV*SOL for Maximum Open Circuit Voltage can also be set in the options. The standard is set to -10°C but can be changed. Due to the temperature coefficient of the open circuit voltage of PV modules, the critical value is reached earlier than under STC conditions. It might be possible to adapt this value automatically taking into account the local climate data plus a certain security buffer; so far you have to adapt it manually.

Kind regards,
Frederik

[Aboud]

Hi Frederik,

 

Many Thanks for your detailed explanation

3 hours ago, developer_fw said:

You are right though that there is no option to set MPP usage to max for example.

I have changed the configuration limits as you suggested, the 'automatic configuration'  worked this time.

 

I am not sure why the software lists many inverter although one inverter was selected. However, I am glad that the  'automatic configuration' was restored after changing the Limits.

 

4 hours ago, developer_fw said:

The maximum system voltage is valid for the modules, be extra careful to not exceed it for not breaking any components with electric arcs. This maximum voltage is not the same as the maximum input voltage of the inverter. Even if the inverter allows for 1100V, your modules might not survive higher voltages. Of course this depends and it might work out nicely. In case there is an accident, no insurance company will be paying for the damage.

Understood. will the software warn you when 'Maximum system voltage' is exceeded as well? regardless inverter Voc as shown below.

 

4 hours ago, developer_fw said:

The test conditions in PV*SOL for Maximum Open Circuit Voltage can also be set in the options. The standard is set to -10°C but can be changed. Due to the temperature coefficient of the open circuit voltage of PV modules, the critical value is reached earlier than under STC conditions. It might be possible to adapt this value automatically taking into account the local climate data plus a certain security buffer; so far you have to adapt it manually.

Many thanks for this information. it is very helpful indeed. Many thanks for your significant effort as well.