André Mermoud

In PVsyst the relevant capacity parameter is th C10 value. It may be slightly different from the rated capacity, usually set for 0.2C (discharge in 5 hours) or 0.5C (discharge in 2 hours). In the above dialog: the stored energy is calculated from the global values just mentoned above: 9830 V * 473960 Ah * 0.9 = 4193.295 MWh. However, in your screenshot, I can't understand the global capacity value of 473'960 Ah. The product 13'872 * 205 in parallel gives 2'843'760 Ah, i.e. as if there were 6 racks in parallel in your Battery pack. I can't reproduce this problem on my PVsyst installation. Probably there is something incoherent in the definition of your battery file. Please send it to us (support@pvsyst.com), in order that we can analyse this problem.

Many questions in a single péost ... Bifacial: I don't see well what you mean by the "calculation in EXCEL". The bifacial model calculation is fully described in the help " Project design > Bifacial Systems" The bifacial feature of the PV modules is described by the only parameter "Bifaciality factor", which is the STC performance of the rear side with respect to the STC performance of the front side. Shading calculations: except with the "Unlimited sheds" option, which uses an analytic calculation in 2D, the shadings calculations require indeed the 3D construction. The Transformer losses may be calculated from the transformer's datasheets parameeters, or generic loss factores for the Copper and the Iron losses. See the help "Project design > Array and system losses > External transformer losses" The auxiliaries losses represent the consumption of auxiliary devices (like cooler, computers, tracker motors, etc) that you want to be "deduced" from your sold electricity in the final balance. PReactive power losses: in the present time, PVsyst doesn't take the impedance (reactive "energy" loss) of the AC circuit and transformers into account. Therefore the power factor defined at the inverter output is the power factor as required by the grid manager.

There is no "a priori" constraints. This completely depends on what you want to optimize, the available area, etc... A "normal" DC:AC ratio, ensuring an oveload loss of, say, less than 1%, would be 1.25 to 1.3 (to be checked by the simulation). Now for some PV plants, the power injection to the grid may be limited by the grid manager. In this case it can be interesting to increase the PV array, in order to produce more energy, at the price of some additional overload loss, and therefore a diminution of the PR. Now the PR is not necessarily the good parameter to be optimized. In many cases this may be the total produced energy, the final system profitability, etc... .

I don't know how you did your calculation. In EXCEL, we calculate:

In PVsyst, the wearing state of the battery is evaluated through two variables: - SOWCycl = wearing state due to cycling - SOWStat = static wearing state (specified lifetime whatever it is used or not). These indicators are evaluated during each simulation. When using the "Aging tool", they are "chained" from one simulation to the next one. This indicates when you have to replace the battery pack. You can get them in the results: These losses are based on the battery definition properties. Now in the reality, the aging of the battery results in a continuous diminution of the capacity. The lifetime is usually defined as the time when you attain 80% of the nominal capacity. The simulation of PVsyst doesn't take this capacity diminution along the years into account. This is not very important, as the Capacity is not a crucial parameter during the system running: a variation of 20% has a very low effect on the final performance.

In the "detailed losses", you can define "Auxiliaries": this defines some auxiliary consumption, which may be a fixed value, or with a part proportional to the produced power (because the cooling needs may compensate the Power inefficiency loss of the inverter, about proportional to the produced power. This auxiliaries is accounted as a loss of the system, i.e. deduced from your PV production when selling it to the grid. Now it is you job to decide which losses you want to include in this contribution, i.e what you want to deduce from the produced energy. The aging tool (button "Advanced simulation" => Aging tool) ") takes the ageing of the battery pack into account from year to year. It will define when changing the batteries if necessary.

In a fixed planes system (sheds), the only effects of the pitch is the mutual shadings, i.e. the shading calculations. In tracking systems with backtracking strategy, the pitch also acts on the tracker's orientation when operating in backtracking mode (i.e. in the morning and evening).

This frame "Medium Voltage line" is supposed to treat the line from the output of this MV transformer to the injection. If you have 3 MV transformers, and one only connexion to the injection, the easiest way is to use the same length and a third of the section of the real line. NB: The objective is to evaluate the resistance of the full circuit, as seen from each MV transformer. If you have more complex circuits, you should calculate the global resistances of all your circuits by yourself, and define sections/length corresponding to your external calculation.

This is explained in our FAQ https://forum.pvsyst.com/topic/44-how-to-define-the-quotmodule-quality-lossquot-and-the-quotlidquot-parameter/#comment-44

Yes, the twin half-cut cells layout is speciified with each module (page "Sizes and technology"). This is taken into account in the "Module Layout calculation", see for example the help " Project design > Shadings > Electrical shadings: Module Layout > Shadings 3D calculation " In the partition in rectangle-strings, you should correctly define the partition. This is explained in the Help " Project design > Shadings > Electrical shadings: Module strings > Partitioning to account for electrical shading losses "

I don't understand well. Your system defines indeed 5 MPPT inputs (1+1+2+1). Are you sure that your inverter is defined with 5 MPPT inputs (this is not in the PVsyst database) ? It probably defines 6 MPPT, so that the number of inverters is 0.83 (with one only decimal). The simulation will work correctly. The only effect would be the possible overload losses, as it is not possible to use the Power sharing option with incomplete inverters.

I have already answered this question in "https://forum.pvsyst.com/topic/3401-modeling-of-inverter-power-limitation-based-on-input-and-output-voltage-also-temperature-derating-for-multiple-input-voltages/#comment-9502

IIn PVsyst, the transformer losses are defined as a sum of - the ohmic losses, proportional to the square of the current or power, calculated at each hour of the simulation. The annual ohmic loss value is not identical to the specified loss fraction, which is specific to a reference power. See the help "Project design > Array and system losses > AC ohmic loss from inverter to injection point". - the iron loss, a fixed constant loss, permanent as soon as the transformer is connected to the grid. This may give a high contribution as it is permanent and doesn't depend on the PV production. See the help "Project design > Array and system losses > External transformer losses"

This PNom deratig according to the input voltage is not yet implemented in PVsyst. PVsyst puts a fixed voltage limit (here 1250 V) for the MPP tracking. However the PVsyst results should be rather correct. They will only be affected if you define high string lenghts (Vmpp close to these maximum operating voltages). As the falling slope of the P/V curve is close to the falling edge of this derating, the overload losses of PVsyst (by displacing the operating point on the I/V curve) are correctly evaluated when the MPP point is over PNom. The conditions for "stopping" the inverter will be similar (see the FAQ just below). https://forum.pvsyst.com/topic/194-why-sometimes-the-overload-losses-increase-significantly-without-reason/#comment-369 NB: This is on our roadmap. We will work on this topic during the next months.

Yes, this is normal. NB: In your voltage definitions, a current of 11A * Voltage of 235V means that you have an inverter with PNom = 11*235 = 2.58 kW (per MPPT input). This doesn't correspond to you previous posts where you had a voltage limitation of 235V for an inverter of 5 kW, i.e. a current of 21.28 A

1. - Temperature derating In PVsyst, there is indeed one only value for the temperature derating Nominal power. However the effect on the simulation will be extremely low because: - The inverter temperature is usually not known/defined with such an accuracy of 2-3 °C at each time step. - There are usually very few hours in the year with such an inverter temperature (this is the environmental temperature around the inverter) - When such temperatures are attained, the error will be effective only when the PV array Power is higher than the PNom of the inverter (overload conditions). 2. - Input voltage conditions This is indeed not implemented in PVsyst. But the behaviour of the simulation is rather close to these limitations. - On the left (low voltages), this corresponds to the input current limitation, defined in PVsyst by the "VmppMin for PMax" parameter (see the help " Component Database > Grid inverters > Grid inverters - Main interface > Grid inverters, main parameters") - On the right (high voltages), this curve corresponds to the increase of voltage when the inverter is in overload conditions (displacement of the operating point). Again, an error in the simulation will only occur in overload conditions, when the falling edge of the I/V curve is close (i.e. crosses) this PNom curve of the inverter. 3. - Grid voltage condition This is not applicable as the Grid voltage is not known during the simulation (it is not an input parameter). Again, this may only affect overload losses, in very particular Grid voltage situations.

We name "Module Mismatch" the mismatch between modules in a PV array. However this is highly dominated by the mismatch due to current differences (i.e. within a string). Because the current of the string is driven by the current of the weakest module in the string. The mismatch in voltage between 2 strings with "reasonable" voltage differences (some few percents) is very low. You have a tool for analyzing this in PVsyst, button "Detailed losses" => "Module quality - LID -Mismatch", page, button "Detailed study".

Thank you for this information. I correct this immediately for the next version.

In practice, the initial SOC for a new system may be anything: the battery from the manufacure may be charged, or not. If it has been stored for a long time, it may be quite discharged. The initial SOC may be specified in the Advanced parameters, topic "Batteries", item #301 "initial SOC for simulation". However this doesn't have any significant importance for a simulation over a long time.

This is on our roadmap. But it involves a very deep change in PVsyst, we will not find possibilities to develop this before probably more than one year.

You are right, the wind velocity measured according to the WMO standards (World Meteorological Organization) specify that the measurement should be done at 10 m height. The Uv value of 1.2 W/m²K / m/s proposed by PVUSA or Tim Townsend is referred to this measurements (i.e. values of all standard meteo data files). This is well explained in the help (topic "Array Thermal losses", paragraph "U-value"):

This is on our roadmap. But sorry, we cannot give a reliable delay. At least several months.

These parameters are basic specifications of each PV module. You can change them within the PV module (using the PV module definition dialog). Then you have to save this PV module as a new PAN file for using it in your simulations.

When defining the AC losses, the loss percentage is proportional to a specified reference power. Now this reference power may be either the POut(AC) when the system is working at STC, or the maximum output power PNom of the inverters. This choice may be done in the project's parameters. See the Help https://www.pvsyst.com/help/ac_ohmic_losses_ref_power.htm In your case, the "STC: Pac = 339 kW" means that the reference power has been chosen as the Pac when the system is running at STC (Nominal PV power = 346 kWp, multiplied by the inverter efficiency). NB: If you change this reference, the relative ohmic loss [%] will change, but not the absolute (real) energy loss in [kW]. NB: PVsyst proposes a cable section, but you may obviously modify this choice.

Please carefully read the help "Performance Ratio" https://www.pvsyst.com/help/performance_ratio.htm The PR corrected for the temperature is a very special evaluation, to help for the evaluation of the global annual PR from a little period data for in-site production assessments.