PV MODULE CHARACTERISTICS

The equivalent circuit of a PV module is shown in Fig. 1(a), while typical output characteristics are shown in Fig. 1(b).
The characteristic equation for this PV model is given by :

I = ILG - Ios * { exp[ q * ( V + I * Rs ) / ( A * k * T ) ] - 1 } - ( V + I * Rs ) / Rsh (4)

where

Ios = Ior * ( T / Tr )3 * exp[ q * EGO * ( 1 / Tr - 1 / T ) / ( B * k ) ]
ILG = [ ISCR + KI * ( T - 25 ) ] * λ / 100

and

I and V cell output current and voltage
Ios cell reverse saturation current
T cell temperature in °C
k Boltzmann’s constant
q electronic charge
KI short circuit current temperature coefficient at Iscr in A/°C
λ solar irradiation in W/m²
Iscr Short-circuit current at 25°C and 1000W/m²
ILG Light-generated current
EGO band gap for silicon
B = A ideality factors (1.92)
Tr Reference temperature °K
Ior Cell saturation current at Tr
Rsh Shunt resistance
Rs Series resistance

The variation of the output I-V characteristics of a commercial PV module as function of temperature and irradiation is shown in Fig. 1(a) and (b), respectively. It is seen that the temperature changes affect mainly the PV output voltage, while the irradiation changes affect mainly the PV output current. The intersection of the load-line with the PV module I-V characteristic, for a given temperature and irradiation, determines the operating point. The maximum power production is based on the load-line adjustment under varying atmospheric conditions.
Fig. 1. (a) Equivalent circuit of a PV module and (b) typical PV module current-voltage and power-voltage characteristics.

Quelques Docs :

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