PV*SOL 2023 Test Version - How to do Power Clipping

[Ricardo Rei]

Dear Team,

I'm using the test version to try some PV*SOL features.

The system that I'm trying to simulate is composed by 2 module areas: 1st area 3 x 110 kW inverters connected to 3 x 255x450 Wp PV modules; 2nd area 2x110 kW inverters connected to 2x 279x 255x450 Wp PV modules. Overall 595,35 Wp DC to 550 kW nominal AC power without consumption. For AC power above 250 kW due to DSO rules the system should have an interconnection protection with several functions, one of those is power feed-in limit. Say that I should limit 20% of power feed-in (110 kW) to a absolute maximum of 440 kW.

Question 1: In "project option" -> "AC Mains" checking the "Maximum Feed-In Power Clipping" box I just have the option "at inverter" not "at feed in-point" (it's grey) why the later option is not available and whats the difference between this two options?

Question 2: If the manufacturer allows to establish a power limit at the inverters, can I simulate this by creating a new versions of the same inverter in the database, by copy paste and then changing the "Max. AC Power in kVA" field "Electric Data - AC"? (I create 110 kW "virtual" inverters with max AC power in kVA of 84 kVA and 94 kV to be applied respectively to the above named 1st and 2nd area: 3x84 + 2x94 = 440 kVA).

Question 3: Trying to understand the behaviour of the diferent power clipping methods (if it can be named like that) I tried some diferent scenarios:

1) Running the simulation with "standard" inverters without "Maximum Feed-In Power Clipping" the grid export is 1 006 272 kWh/year;

2) Running thes simulation with "standard" inverters with "Maximum Feed-In Power Clipping" 440 kW "at inverter"  the grid export is 962 356 kWh/year;

3) Running thes simulation with "virtual" inverters (limited at 84 kVA and 94 kVA) without  "Maximum Feed-In Power Clipping", the grid export is 962 386 kWh/year;

4) Running thes simulation with "virtual" inverters (limited at 84 kVA and 94 kVA) with  "Maximum Feed-In Power Clipping" 440 kW, the grid export is 960 722 kWh/year;

If grid export at scenario 2 is lower than the scenario 3 why then the grid export is even lower in scenario 4 (that actually merges scenario 3 and, more resctrictive scenario 2, regarding power clipping options)?

Which of the above scenarios should be adopted?

Thank you in advance.

Kind regards,

Ricardo

[developer_fw]

Hello Ricardo Rei

thank you for your request.

Might you be so kind and send the project file(s) via private message here in the forum?

There could be differences/greater errors when simulating with hourly values.

Thank you in advance and kind regards
Frederik

[Peter_]

Hi Ricardo,

regarding question 1: In order to make the "at feedin" option box  clickable you need to add an own-consumption.   

you can change the type of system to as follows: change the type of system to gridconnected with electrical appliances.

if you dont have any own consumption then I would suggest adding a yearly consumption of 1kwh as this is neglectable 

The main differences between the two options is,as the name says,  where the feed-in power clipping is done. in the first option you will clip at the inverter,  550 kW nominal AC power is always clipped at the inverter to 440kw. 

However if you have an own consumption, you dont want to reduce the power of the pv system at the inverter because you can use its electricity yourself. hence you want to clip at the feed in. in that case after own consumption you check at the grid connection if the power is 440kw and if it is more it will do the feedin power clipping.

** note: in practical situation the grid feed in meter sends a value to the controller and the controller active-dynamically adjusts the inverter output ** 

if you dont have own consumption you can check either options however be aware of the following:

if you check inverter clipping it shows it in PV system energy balance as down regulation on account of the max ac power/cos phi.

  

however if you use grid feed in checkbox. It does not show in the energy balance  because the  clipping is done at feed in   (which isnot in the scope of the pv system energy balance)

in that case look at the simulation results where it shows:

 

hope it helps!