Method for determining an electrical model of a string of photovoltaic modules, diagnostic method and device associated therewith

Patent metadata

Field	Value
Publication number	US-2020151379-A1
Application number	US-201916682807-A
Country	US
Kind code	A1
Filing date	Nov 13, 2019
Priority date	Nov 14, 2018
Publication date	May 14, 2020
Grant date	—

Abstract

A method for determining an electrical model of a string of photovoltaic modules from a characteristic I(V) of the string includes detecting a first linear zone and a second linear zone of the characteristic I(V); initialising the parameters of a non-by-pass electrical model corresponding to a first operating condition, called a non-by-pass condition; optimising the parameters of the non-by-pass electrical model from a reference characteristic I(Vref) equal to I(V), determining the parameters of the electrical model corresponding to a second operating condition, called a by-pass condition, in order to obtain a by-pass electrical model from the characteristic determining, from the characteristic I(V) the best model among the non-by-pass model and the by-pass model.

First claim

1 . A method for determining an electrical model of a string of photovoltaic modules from a characteristic I-V of said string and a non-by-pass model corresponding to a first operating condition of the string, called a non-by-pass condition, given by the following equation:

Y
=

I
ph

-

W
th

+

R
s

×
Y

R
p

-

I
0

×

(

e

W
th

+

R
s

×
Y

N

-
1

)

with I ph the photocurrent, R s the series resistance, R p the parallel resistance, I 0 the dark current of the diode,

N
=

k
q

×

N
s

×

T
ideal

with T ideal ∈[200,300], N s the number of series cells in the string, k b is the Boltzmann's constant and q is the elementary charge of a proton, Y the current passing through the string and W th the voltage across the string; and a by-pass model corresponding to a second operating condition of the string, called a by-pass condition and given by the following equation:
W mod ( Y )= W 1 ( Y )+ W 2 ( Y )

with W mod the voltage across the string according to the by-pass model for the current Y,

W
1



(
Y
)

=

(

1
-

P
d

)

×

W
th



(
Y
)




and




W
2



(
Y
)

=

P
d

×

W
th



(

Y

1
-

P
I

)

where W th (Y) is the voltage across the string given by the non-by-pass model, P d the by-pass diode proportion and P I the short-circuit current loss proportion induced by the by-pass, the method comprising:
a step of detecting a first linear zone and a second linear zone of the characteristic I-V;
a step of initialising the parameters of the non-by-pass electrical model from the characteristic I-V;
a step of optimising the parameters of the non-by-pass electrical model from a reference characteristic I(V ref ) equal to I(V);
a step of determining the parameters of the by-pass electrical model, in order to obtain a by-pass electrical model from the characteristic I-V;
a step (E 6 ) of determining, from the characteristic I-V, the best model from the non-by-pass model and the by-pass model.

2 . The method according to claim 1 , further comprising, before the step of detecting the linear zones of the characteristic I-V, a step of checking the data of the characteristic I-V.

3 . The method according to claim 2 , wherein the step of checking the data of the characteristic I-v comprises at least one of both following sub-steps:
a sub-step of detecting the switching period of the string, the data measured outside the switching period being removed; a sub-step of removing the outliers.

4 . The method according to claim 1 , wherein the step of detecting a first linear zone and a second linear zone of the characteristic I-V comprises:
a sub-step of determining the maximum power point (I MPP , V MPP ), the points of the characteristic I-V located above the straight line passing through the origin (0,0) and the point (I MPP , V MPP ) being considered as candidates for the first linear zone, and the points located below this straight line being considered as candidates for the second linear zone; a sub-step of determining the linear model of the current Y as a function of the voltage W across the string such that Y=a sc ×W+b sc from the candidate points for the first linear zone and the linear model of the voltage W across the string as a function of the current Y such that W=a oc ×Y+b oc from the candidate points for the second linear zone, so as to determine the parameters a sc , b sc , a oc and b oc .

5 . The method according to claim 4 , wherein during the step of initialising the parameters of the non-by-pass electrical model, the parameters of the electrical model I ph , R s , R p , I 0 and N are initialised in the following way:
R p is given by

Assignees

• Commissariat Energie Atomique

Inventors

• Lespinats Sylvain

Classifications

• G06F30/367 Primary

  Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods · CPC title

• G06F2119/06

  Power analysis or power optimisation · CPC title

• H02S50/10

  Testing of PV devices, e.g. of PV modules or single PV cells (testing of semiconductor devices during manufacturing {H10P74/00}) · CPC title

• G06F2111/10

  Numerical modelling · CPC title

• G06F30/00 Primary

  Computer-aided design [CAD] · CPC title