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    How can i chose the resistor value to simulate a PV cell in ADS

    Hello all ;

    How can i chose the value of the resistor (Rs and Rsh) to simulate a PV cell (electrical circuit model)?

    Regards ,

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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    This may be to late! Rs can be calculated from the voltage drop from VOC to VMPP divided by IMPP that are all normally quoted both for panels and cells. Rsh (shunt ?) in the forward sense is immaterial as it is shorted by the junction anyway, in reverse I have not seen it quoted but would be the typical reverse breakdown characteristic of a junction, so a wee bit of leakage followed by a sharp breakdown at the reverse voltage rating. I think from memory I used a meg. Unfortunately all my models are in LTspice so not much help to you.



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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Is the question about a photovoltaic panel? I did measurements on my solar panels, and I found they put out greatest voltage when unloaded (0 Amperes), and greatest Amperes at 0V. However both those conditions produce no Watts. There is a middle range where maximum power is conveyed.

    A 12V pv panel puts out 18-23v unloaded. Therefore when I simulate a 12V PV panel, I create a 24v source, and add an inline resistor equal to the ohm value of the load. This automatically creates 12V to the load.

    If load is removed, voltage rises above 20v (as occurs with a real pv panel).

    If I'm charging a battery, more current flows when the battery is weak, and less current flows as the battery rises to 15v. (Same behavior with a real pv panel.)

    When I first tried to simulate a pv panel I used a plain voltage source. This is incorrect. Something needs to be added so the voltage drops as you draw more Amperes from the PV panel.
    (Is that the resistor which the question refers to?)



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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Hello Brad, well let me help you out there, the correct way to model a PV cell is as a CURRENT source in parallel with a forward biased diode who's characteristics (conduction knee) mimics your cell. The output of the cell is then taken from this combination via Rs (R series). Rsh (R shunt) is across the parallel combination of current source and diode. The magnitude of the current source is controlled between 0 & Isc according to irradience. Panels are built up of as many of these cells as you have in your panel in series, shading diodes can also be added to complete your panel model. If your model is correct the plot of power vs voltage should match the panel manufacturers data.

    Hope this helps :)


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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Hello all ;
    Thank you for your reply all;
    Actually i have this curve, and i want to have the Rs (series resistor) and the Rsh (shunt resistor ) of this curve. According to the author the Rs and Rsh are given by the slope near to the open circuit voltage and short circuit current respectively .
    The value i got it in form this curve is ordre of few ohms!!!?? Is it correcte ??
    Please, can someone help me to obtain these values of the resistors ??

    Click image for larger version. 

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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Quote Originally Posted by So.nia View Post
    The value i got it in form this curve is ordre of few ohms!!!?? Is it correcte ??
    I measured my photovoltaic cells under the sun, loaded by various resistors. I took V & A readings for each ohm value. I made a computer program to calculate Watts (V x A), and to plot the data.

    Below is my graph showing how real PV cells perform under load. At the extreme ends it's obvious you can have high A, low V, or vice versa. Both yield minuscule Watt output.

    Highest Watt output occurs at the middle region of the graph. Load 6 ohms.

    Click image for larger version. 

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    Impedance matching is associated with maximum power transfer, so this means 6 ohms was the effective internal impedance of the PV source. As for how to simulate the same performance using ordinary component models, that's the tough part.



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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Quote Originally Posted by So.nia View Post
    Hello all ;
    Thank you for your reply all;
    Actually i have this curve, and i want to have the Rs (series resistor) and the Rsh (shunt resistor ) of this curve. According to the author the Rs and Rsh are given by the slope near to the open circuit voltage and short circuit current respectively .
    The value i got it in form this curve is ordre of few ohms!!!?? Is it correcte ??
    Please, can someone help me to obtain these values of the resistors ??
    Click image for larger version. 

Name:	PV_Cell.png 
Views:	5 
Size:	42.6 KB 
ID:	152298
    Unfortunately I have no knowledge of the model you are using so I cannot directly answer your question.
    In my case in spice most published models I am aware of use a diode shunting a current source and it is the diode characteristics that are most critical, Rs simply being added to represent the interconnect resistance. Who is the Author you are referring to ?
    Is this an educational question or are you developing models for practical use ?

    I wonder if the model you have does not have a shunt diode to control VO but rather just a shunt resistor, sounds implausible but possible, please can you publish the schematic or netlist of your model ?

    Bradtherad, the OP is asking about how to model something NOT how it works in practice.



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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    Quote Originally Posted by fourtytwo View Post
    Unfortunately I have no knowledge of the model you are using so I cannot directly answer your question.
    In my case in spice most published models I am aware of use a diode shunting a current source and it is the diode characteristics that are most critical, Rs simply being added to represent the interconnect resistance. Who is the Author you are referring to ?
    Is this an educational question or are you developing models for practical use ?

    I wonder if the model you have does not have a shunt diode to control VO but rather just a shunt resistor, sounds implausible but possible, please can you publish the schematic or netlist of your model ?

    Bradtherad, the OP is asking about how to model something NOT how it works in practice.
    I use this model (In Fig).
    Actually i need to simulate the next stage (Switch converter). but i don't have the value (Rsh,Rs, Diode) and i don't have idea to get them ??!!Click image for larger version. 

Name:	PV_Cell_Model.png 
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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    You get the shown I/V curves basically by using a current source and a silicon diode. R and Rsh are only slightly modifying it. Did you ever try?



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    Re: How can i chose the resistor value to simulate a PV cell in ADS

    I wish you had posted that model originally then we would have had a clearer idea what your problem was. FYI here is my standard spice model I use.
    Click image for larger version. 

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    As you can see Rser is tiny as I explained before it is only the interconnect resistance and Rsh is huge simply representing leakage. The major characteristic is determined by the diode hence the custom model (I don't know if ADS is spice compatible).

    If you want to ask about converters it might be an idea to start a new thread to avoid confusion.


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