traj123

Hey Andre, Is the E-W mis-align with bactracking plan to be introduced in PVsyst in upcoming versions? Is there a timeline on it? Thanks! Taran

Hi all, I am hoping to get some advice on exactly how to use the external transformer losses in PVsyst 5_56. 1) Is it possible to calculate the Iron and Resistive/Inductive losses from the Transformer input, output, X/R and %z values? 2) Could you please give me an example of exactly what specifications I need to look for in a transformer to fill out the PVsyst requirements. Thanks,

Very interesting question indeed and one that has been debated for a while now. To add to what Marvin mentioned, I think that constantly operating the inverter at a higher voltage (yet within its limits), while shifting the MPPT seems to have unintended consequences that inverter manufacturers don't seem to be very clear about. I've hear a wide range of speculation ranging from DC:AC ratios not exceeding 1.12 to ones above 1.5, and some of the impacts particularly with instantaneous spikes in current when the inverter is constantly operating in the steeper part of the curve is still an open question. On the other hand, with Marvin's second and third points, I'm a little confused, since correct MPPT tracking would imply that the energy from the modules was never realized. This would imply that there shouldn't be a temperature derate effect due to over-powering either at the inverter or the module, since the area under the IV curve is itself reduced, so the power is never produced. So, could you please clarify your points Marvin?

Hi Marvin, Thanks for your response. So, per your explanation the nominal power gets split evenly between the MPPTs in multiple MPPT inverters. You also state that, "If you are using the same rating modules in both strings you will have more power from one string than the other and if this results in one MPPT input being overpowered or underpowered it will effect the results since PVsyst is going to split the power 50/50." I have a couple of follow up questions based on that: 1) So if the 12 module string overpowers its respective MPPT, its (ONLY that MPPT) output gets clipped to 50% of the nominal rating of the inverter. However, this seems like the correct response expected. Am I correct? 2) If multiple MPPT systems require 2 subfields defined, then would you happen to know why PVsyst 5 has the entry for number of MPPTs in the inverter file? Since it appears that each MPPT needs to be modeled separately. 3) Can you direct me to a data sheet of an inverter with asymmetric power ratings for its MPPTs. I looked at the SMA Tripower series and didn't see anything different relating to this. 4) Lastly, could you please clarify this point "If you have multiple inverters with multiple MPPT inputs you have to assign the number of MPPT inputs to the subfield that is equal to the power output of that subfield. The fewer inverters you have the closer to a 50/50 power split the subfields have to be" Thank you very much!! Taran

Hi Andre, Could you please clarify exactly what you mean with the following example: Scenario 1: Inverter A - 1 MPPT 2 strings of 11 modules in parallel to the input Scenario 2: Inverter B - 2 MPPT 1 string of 10 modules to first input 1 string of 12 modules to second input How would I model these two scenarios in PVsyst? Also, as far as I understand, inverters with multiple MPPTs can be have different string configurations connected to them. So what is the difference between a regular inverter with 2 MPPTs and an "unbalanced inverter" with 2 MPPTs? Thanks, Taran