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Lazare Fesnien

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Posts posted by Lazare Fesnien

    Number of modules in series

    in Problems / Bugs

    Posted

    Dear Moataz,

    In the system tab, when choosing the PV module, PVsyst displays the voltage Voc at -10°C. It is this value which is taken into account for the calculation of the maximum number of modules in series.

    Absolute Cell lower temperature for determining the Maximum possible voltage of the array. The default is set to -10°C for most European countries (best practice rule).

    For this limit, the cell temperature is considered as the ambient temperature (worst case when the sun suddenly appears on the field).

    You should define the lowest temperature ever observed during the day for this site.

    NB: these parameters are used for design only. They are not involved in the simulation in any way. 

    Please read : https://www.pvsyst.com/help/inverter_array_sizing.htm?zoom_highlightsub=Array+voltage+sizing

     Regards

    Capture d’écran 2023-03-03 132136.jpg

    Reactive power

    in Simulations

    Posted

    Dear Said Allaw,

    The "Reactive power" is not a real electrical power: you cannot produce any movement or heat with it.

    Reciprocally, the production of reactive power doesn't consume any "real" (active) energy.

    Now the output electronic circuits of some inverters are able to "produce" a reactive power on the grid, by "absorbing" power from the grid and "reinjecting" it with a phase shift. They may behave in the same way as a capacitor for "absorbing" reactive energy  (or possibly an inductor, but this is not useful). This feature is sometimes provided by PV plants to the grid, especially during night.

    This contribution is not treated by PVsyst, as it is not related to the PV production. PVsyst only treats the Reactive power associated with a PV "active" power  production. The reactive power treated in PVsyst is always proportional to the Active power.  

     

    The operating value will depend on the available irradiance. This always produces the active power  (POutInv = Parray * inverter efficiency).

    Now if you have defined a phase shift, the inverter will also produce a reactive  “power”  POutInv_R  = POutInv  * Sin(Phi).  But this doesn’t consume any additional power.

    Reactive and apparent energy values in the loss diagram

    in Simulations

    Posted

    Dear Said Allaw,

    PVsyst treats the Reactive power (or energy) linked to the PV production.  This is done by a constant factor (Cos(Phi)) specified/required by the Grid manager. This reactive power is proportional to the produced energy.

    See the help " Project design > Grid-connected system definition > Power Factor".

    A reactive power may be created or absorbed, depending on your definition (Leading or Lagging power factor)

    CABLE SECTION

    in How-to

    Posted

    Dear Ayad,

    The ohmic resistance of the wiring circuit induces losses ( ELoss =  Rw · I² ) between the power available from the modules and the power at the terminals of the sub-array.

    The relevant parameter for the simulation is the Rw value, which is an  equivalent resistance of the wires, as "seen" from the input of the global sub-array  (i.e. the set of MPPT inputs defined in this sub-array). You should define one Rw value for each sub-array in your system.

    A PVsyst tool allows you to easily calculate this information in "Detailed Losses" then "Ohmic Losses" then "Detailed Computation"

    Regards,

    Vmp and Imp RMS disperion values (Ageing tool)

    in Simulations

    Posted

    Hi,

    You can account for the aging of the PV modules in ‘Detailed losses -> Aging’. This allows you to make a simulation for one specific year of operation. You can also make multi-year simulations in ‘Advanced simul. -> Aging tool’.

    PVsyst will not change the nominal power of the PV modules, but simulate with a model of degraded PV modules. This means that the performance ratio PR will decrease with time, since nominal power stays the same, but effective generated power will decrease.

    The aging of inverters is not modeled in PVsyst.

    For more explanations on how to use the aging tools of PVsyst, please see the corresponding help page : https://www.pvsyst.com/help/ageing_tool.htm

    Available energy Stand Alone vs Grid Tied

    in Simulations

    Posted

    Hi,

    This difference is due to several reasons : 

    - In grid connected, the inverter has effective MPPT inputs to seek the maximum power point

    - Stand alone, regulators with MPPT don't have good efficiency.

    In the grid connected system, losses and gains are put by default in the tab "detailed losses" it's necessary to look at the two complete reports to visualize the differences.

    How can I correct this

    in How-to

    Posted

    Hi, 

    The value 165.6 MWh corresponds to the energy injected into the grid (coming from your PV production). 

    The value 158.9 MWh corresponds to the energy needed from the grid to supply your load profile.

    When your production is greater than you load profile, energy has to go  somewhere, either into batteries or into the grid.

    If you want to use only the energy of your PV array, you must either modify your load profile or set up a battery park.

    Regards

    Power factor doesn't affect energy output

    in Simulations

    Posted

    Hi, 

    Remember that the Active Power [kW] =  Apparent power [kVA] * cos(Phi).

    The real power (i.e. corresponding to a useable energy) is indeed the active power. This is what is produced by the PV array and transformed by the inverter into output power.

    The apparent Power  is the quadratic sum of the active power and the reactive power. But the reactive power IS NOT A POWER.  You cannot produce movement or heat with it.

    If the limit is specified as Active power, the actual limit is completely independent on the Power factor.

    How to set Series and Shunt Resistance?

    in How-to

    Posted

    Hi,

     In case of doubts, you should use the default values of PVsyst:

    • Rshunt and Rserie in order to get a low-light relative efficiency of -3%.

    You can play with these parameters. Please carefully read the Help " Physical models used > PV Module - Standard one-diode-model > Rseries and Rshunt determination procedure".

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