# pvl_est_Rs_Pysch

PVL_EST_RS_PYSCH Estimate Rs using the method of Pysch.

## Contents

- Syntax
- Description:
- Inputs:
- Outputs:
- Example
- References:
- See also

## Syntax

- `[Rs, errest] = pvl_est_Rs_Pysch(IVCurves, delI)`
- `[Rs, errest] = pvl_est_Rs_Pysch(IVCurves, delI, Rsh, nNsVth, Io)`

## Description:

The method of Pysch [1] extends the Swanson method to use multiple IV curves. IV curves are assumed to be at different irradiance levels but the same cell temperature. A point is selected on each IV curve where the current is less than Isc by the input delI. If optional arguments are provided, the difference between the returned Rs value and the Rs parameter for the single diode equation is estimated, see [2].

## Inputs:

- `IVCurves` - a structure array for IV curves including fields V and I.
- `delI` - offset from short circuit at which to choose IV curve points.
- `Rsh` - (optional) a vector of shunt resistance, in ohms, for each IV curve.
- `nNsVth` - (optional) a vector containing the product n (diode factor) x Ns (cells in series) x Vth (thermal voltage per cell) for each IV curve.
- `Io` - (optional) a vector of the dark current, in A, for both IV curves.

## Outputs:

- `Rs` - the series resistance value in ohms.
- `errest` - the estimated difference between Rs and the series resistance parameter for the single diode equation.

## Example

    clearvars

    % Set up parameters for a representative 60 cell cSi module using the Desoto model
    Const.q = 1.60218E-19;
    Const.k = 1.38066E-23;
    Const.E0 = 1000;
    Const.T0 = 25;

    param.aIsc = 0.0008;  % A/C
    param.bVoc = -0.1900; % V/C

    param.Rs_ref = 0.2;
    param.Rsh_ref = 1000;
    param.IL_ref = 8.0;
    param.I0_ref = 5e-10;

    param.a_ref = 1.05 * 60 * Const.k/Const.q * (273.15 + Const.T0);

    EgRef = 1.121;
    dEgdT = -0.0002677;

    % Calculate set of IV curves
    Ee = 900:20:1100;
    Tc = 25;
    nPts = 100;
    for i=1:length(Ee)
        [IL, I0, Rs, Rsh1, nNsVth] = pvl_calcparams_desoto(Ee(i), Tc, param.aIsc, param, EgRef, dEgdT);
        IVcurves(i) = pvl_singlediode(IL, I0, Rs, Rsh1, nNsVth, nPts);
    end

    % Current differential
    STCidx = find(Ee==1000);

    delI = 0.95*(IVcurves(STCidx).Isc - IVcurves(STCidx).Imp);

    % Estimate Rs
    Rs = pvl_est_Rs_Pysch(IVcurves, delI)

    Rs =

        0.2180

## References:

- [1] D. Pysch, A. Mette, S. W. Glunz, “A review and comparison of different methods to determine the series resistance of solar cells", Solar. Energy Materials and Cells 91, pp. 1698-1706, 2007.

- [2] C. Hansen and B. King, "Determining series resistance for equivalent circuit models of a PV module", in 45th IEEE Photovoltaic Specialist Conference, Waikoloa, HI, 2018.

## See also

`pvl_est_Rs_Bowden` , `pvl_est_Rs_Swanson` , `pvl_est_Rs_sunsVoc` , `pvl_est_Rs_IEC60891_1` , `pvl_est_Rs_IEC60891_2`

Copyright 2018 Sandia National Laboratories