André Mermoud

I don't know if this error is due to the size of the plant. However the "Module Layout" part is not suited for such big plants: see our FAQ How to use the Module Layout with very big plants?

In PVsyst (as in the reality) the overpower conditions is indeed achieved by a displacement of the operating point on the I/V curve (towards higher voltages). But in the present time PVsyst doesn't take the possible overpower (defined by some manufacturers) into account. See the FAQ How PVsyst treats the specified "maximum" power of inverters ?

The design of the PV array (namely the number of modules in series) uses a set of design temperatures, used at the design time only for parameter suggestions or system configuration checks. These temperatures may be specified for your project (button "Albedo-Settings"), and their default value for any new project may be specified in the Hidden parameters, topic "System design parameters". - TMin: Lower temperature for Absolute voltage limit: The Voc(Tmin) requirement corresponds to a safety requirement: The array voltage Voc should never overcome, in any case: - neither the inverter's VabsMax (absolute input voltage, corresponding to the input electronics circuit voltage limit), - nor the absolute array maximum voltage admitted for your PV modules (usually 1000 or 1500V). Therefore the reference temperature for this evaluation is the lowest temperature even observed on this site. - In middle-Europe climate (and not in altitude), a usual best practice is to choose -10°C. But this should be decreased for high altitude or northern regions. - In other situations, you should take the lower temperature ever observed during the day (eventually with an irradiance superior to 10 W/m2) for this site. Choosing 1000 W/m2 means that in worst case, in winter the sun may suddenly appear on the array (cloud), and in this case the cell's temperature may be the ambient temperature. Remember that the Voc is very slightly dependent on the irradiance. These conditions are a common practice, adopted by everybody. They are specified in the norm IEC TS 62738 (2018), paragraph 7.2.1. Now if you want to overcome these constraints (which is really not recommended), you can: - modify the reference low temperature in the Project's parameters (button "Project Settings"), - modify the muVoc coefficient if you don't believe the PVsyst's model value (in the PV module definition, page "Additional data > Secondary parameters" ). - artificially increase the maximum voltage limit in the Inverter's and/or PV module's definitions. NB: These modifications will alter the warranty of your PV system. If you do that this will be at your own risks. - ToperMin and TOperMax: the usual operating conditions of your array, during winter and summer (cell temperature). ToperMin will be used for the maximum number of modules in series, in order to stay below the VmppMax input value of the inverter. ToperMax will be used for the minimum number of modules in series, in order to stay above the VmppMin input value of the inverter. These values are not critical, and may usually be let to their default values. Slightly overcoming the voltage limits doesn't induce important losses (in case of doubtful sizing, you will observe an "Inverter loss over nominal voltage" or "Inverter loss due to voltage threshold" in the loss diagram of the simulation). - TOper: Usual operating (cell) temperature under 1000 W/m2, is an intermediate value, only used for the display of a usual "operating power" in the sizing dialog (and the report). In the version 6, these definitions are part of the parameters of your project, button "Albedo and Settings". They may eventually be modified according to your climate. The default values (initializing value for each new project) may be redefined in the Hidden Parameters, topic "System design parameters". These parameters are used for design only. They are not involved in the simulation in any way.

In the next version 6.18, there will be an "Hourly-Monthly" table of E_Grid, i.e. the production of each hour of the day for each month. You will be able to export it in EXCEL, and associate your specific tariff to each hour of each month.

The mismatch effect with strings in different orientations is indeed taken into account in the simulation with Heterogeneous fields "mixed orientation". However the mix of 2 strings in 2 orientations will have different currents, but about the same voltage: this doesn't produce a significant mismatch loss.

This is just a pedagogical tool, for understanding the mismatch phenomenon on one I/V curve. You can evaluate the mismatch loss between 2 different sub-arrays with strings in different orientations, connected on a same MPPT input, by performing a full simulation using the option "Heterogeneous fields - Mixed orientation", and compare with the results of 2 different systems in each orientation. For parallel strings, the mismatch effect due to different orientations is usually very low.

I can't reproduce this problem. It works quite well on my machine. Does it arise for any system, or just for a particulat one ?

This is a feature of the Forum engine. We don't know how to manage it.

In stand-alone (or pumping) systems, the Unused energy is the energy which could be provided by the PV array, but which cannot be used because the battery is full. I don't understand "Horizontal Global Orientation". This doesn't have any meaning. The Global horizontal irradiance is determined by the meteo data of the location. The orientation of the collectors is your choice. The irradiance in this plane is indeed dependent on the azimuth of your chosen plane orientation (through the "Transposition" model). The output of a PV module is the EArrNom value "array virtual energy at MPP", calculated from the one-diode model.

This should not damage the inverter. For the PV modules, it should be without effect except if some by-pass diode is damaged. In this case you can have hot-spot problems. NB: The by-pass diodes are usually Shottky devices, with a reverse maximum voltage of the order of 30V. They may sometimes be damaged by electromagnetic fields due to nearby lightnings, especially if the connections of your strings are not well "grouped". The induced parasitic voltage is proportionnal to the conductor's (string) loop area.

You should be able to define two different sub-arrays, with the same orientation ("Fixed tilted plane"). I did not try this but at first sight I don't see what would prevent this in the program. Let me know if there is a problem.

There is probably a problem with the driver of your active printer. Please try simply to change the default printer in your Windows installation. If this doesn't work,you can download the free tool PDFCreator (to be installed as a printer): http://www.pdfforge.org/products/pdfcreator And choose it as Default printer. To my knowing this works in any case.

You can have a look on the Loss diagram at the end of the report, and estimate whether the losses due to shading are acceptable for you.

This is another question. Here Ext is for "external" indeed. The waited value is the ambient dry bulb temperature, averaged over the month. A realistic daily profile will be constructed by the Synthetic hourly data generator, taking the concomitent irradiance into account. This will construct a sinus-like profile, with amplitude about proportionnal to the daily irradiance, and a delay of 2-3 hours (i.e. by clear day, the peak temperature is around 15H (solar time)). This model waits for the real average over 24H, not the "Average Daytime Temperarture" proposed by some databases.

In the present time, the only way of defining properly the terrain shape is to import a full system from the Helios3D program. When importing a system from this tool (with tilted basis sheds following the terrain), there is indeed a distribution of several "true" orientations and PVsyst works with an averaged value. However this possibility is not yet developed for systems directly developed within PVsyst. We will indeed think about a way of easily defining the terrain and PV tables on it for a next version, but probably not before some months.

Sorry, this problem was introduced n the version 6.16 by accident, and will be corrected in the next version 6.17, which will be released hopefully on 10/01/14

You should define the degradation effect using the "Module quality loss" parameter. Please see our FAQ How to define the "Module Quality Loss" parameter ?

The temperature specifications during the sizing - which you specify in the "Project's parameters, button "Albedo-Settings" - is only used for sizing purposes. It should give indications about the number of PV modules in series. You have a full explanation in the help "Project design > Grid-connected system definition > Array voltage sizing" - The "Lower temperature for absolute values" concerns the safety of the system: it is an "absolute" limit value. - The "Winter, Normal and Summer operational temperatures" have a low importance during the design (see the graph in the help or on the sizing tool). You can slightly overcome the MPP voltage limits without significant losses. The final test of the validity of your choice for the number of modules in series will be the Inverter loss below the minimum and over the maximum voltage during the simulation (on the loss diagram). NB: During the simulation, the array temperature is determined from the hourly ambient temperature and the irradiance, using a little energy balance model.

In the "Module Layout" part, you can analyse the electrical effect of a shade by clear sky conditions (when the modulelayout configuration is well defined, using the "Shading 3D" sweep, => "I/V curve"). This is indeed not simple ! You will see that with several strings in parallel, when one string is shaded the voltage of the MPP usually doesn't drop. As a contrary, with one only string per MPPT, the voltage drop due to beam shading may be important according to the shaded cells. However with a high diffuse ratio the "best" MPP will usually stay on the curve representing the diffuse, i.e. without significant voltage drop.

You are right. There is a problem above 10 MW, the unit change doesn't work correctly. You should indeed specify the value in kW although the displayed unit is in MW. I have corrrected for the next version 6.17.

The NEDO web site referenced above is fully in Japanese language. As we don't have Japanese people here at PVsyst, you can understand that we cannot propose anything for importing these data. Are these data in Hourly or in Monthly values ? If they are in hourly values, please us send a sample file, and we will see what we can eventually do with it.

The possibility of defining "heterogeneous fields" (multi-orientations), also with inverters mixed between orientation #1 and #2, is available in PVsyst since the beginning of the version 4. However in the versioon 6.13, you can define up to 8 orientations (and a "mixed" inverter between orientations #1 and #2), without the previous limitations about the mutual orientation difference limit.

For adjusting the maximum output of an inverter, you can simply modify the "Nominal AC Power" parameter in the definition of the device, and save it with under another filename, therefore creating a new device in your database. In your case you will define 1 sub-array with 2 normal 500 kW inverters, and one sub-array with your new 400 kW. Now since the version 6.11, under the button "Miscellaneous tools", you can limit the power of the whole system to a specified value. However the simulation will limit all Inverters identically, to a Pnom = 1400/3 kWax value.

We don't know how to access the Nedo database. Is is public ? Which kind of data does it provide ?

We cannot say anything if you don't mention which kind of wrong data. Please explain.