**2.2. I-V and P-V generation curves**

Under the specified Standard Test Conditions, expressed by (2), PV modules are tested and featured by I-V (current versus voltage) and P-V (power versus voltage) curves, in which the effect of solar radiation and temperature on the PV generated power is evidenced.

$$\begin{aligned} \text{S } \,^{STC} &= 1000 \text{ W/m}^2\\ T \,^{STC} &= 25 \,^\circ \text{C} \\ AM \,^{STC} &= 1.5 \end{aligned} \tag{2}$$

Although both, solar radiation and temperature, are strongly coupled, solar radiation pre‐ dominantly influences the PV module output current, while temperature mainly changes the PV module output voltage, as depicts the I-V curve presented at Figure 4, obtained from Kyocera KC200GT PV module datasheet.

One of most important PV module operation point is obtained on the knee of the I-V curve. In this point, named by maximum power point (MPP), the product of the PV output voltage and current results at the maximum available power, for a given solar radiation and temper‐ ature. For emphasizing the maximum power point, an alternative P-V (power versus volt‐ age) curve may be plotted, in accordance with Figure 5.

Mathematical expressions for calculating the PV module output voltage *V mpp* and current *I mpp* on MPP are given by (3) and (4), whose product results on the PV output power *P mpp*, according to (5) [21], where:

*Vmpp*, *Impp*, *Pmpp* : PV module output voltage, current and power on MPP for any irradiance (*S*) and surface temperature (*T*);

*V mpp STC*, *I mpp STC*, *Pmpp STC* : PV module output voltage, current and power on MPP. These parameters are obtained from datasheet and specified on STC (*T STC* and *S STC*);

*μV* , *μA* : Temperature voltage coefficient (V/◦C) and temperature current coefficient (A/◦C). These parameters are also obtained from datasheet.

$$V\_{mpp} = V\_{mpp}^{STC} + \left(T - T^{STC}\right)\mu\_V \tag{3}$$

er is null, but the output current or voltage reach the maximum value, respectively. Figure 6

An Optimized Maximum Power Point Tracking Method Based on PV Surface Temperature Measurement

http://dx.doi.org/10.5772/51020

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**Figure 5.** P-V curve from Kyocera KC200GT PV module obtained by simulation: (a) under constant temperature and

For maximizing the PV conversion efficiency, the incoming sun energy must be converted to electricity with the highest efficiency, accomplished when the photovoltaic module operates on the maximum power point. Nevertheless, since this operating point is strongly affected

highlights *I sc , V oc*, *I mpp*, *V mpp* and *P mpp* on both, I-V and P-V curves.

**Figure 6.** Identification of *Isc, Voc*, *Impp*, *Vmpp* and *Pmpp* on the I-V and P-V curves.

**3. Maximum power point tracker**

(b) under constant solar radiation.

$$I\_{mpp} = \frac{S}{S} \frac{S}{S^{STC}} I\_{mpp}^{STC} + \left(T - T^{STC}\right) \mu\_A \tag{4}$$

$$P\_{mpp} = \frac{S}{S} \frac{S}{STC} P\_{mpp}^{STC} + \left\{ T - T^{-STC} \right\} \left( \frac{S}{S^{STC}} \mu\_V I\_{mpp}^{STC} + \mu\_A V\_{mpp}^{STC} \right) + \left\{ T - T^{STC} \right\}^2 \mu\_V \mu\_A \tag{5}$$

Note that (5) is useful once it allows estimating the amount of available PV power only from the environmental data (*S*, *T*). All other related parameters are commonly specified on PV module datasheet. For instance, considering the KC200GT PV module, the following data‐ sheet specifications are found:

**Figure 4.** I-V curve from Kyocera KC200GT PV module: (a) under constant temperature and (b) under constant irradi‐ ance.


**Table 1.** PV module specifications on STC from Kyocera KC200GT PV module datasheet.

Furthermore, short circuit current (*I sc*) and open circuit voltage (*V oc*) are also important for a complete PV module characterization. They remark the points where the PV generated pow‐ er is null, but the output current or voltage reach the maximum value, respectively. Figure 6 highlights *I sc , V oc*, *I mpp*, *V mpp* and *P mpp* on both, I-V and P-V curves.

**Figure 5.** P-V curve from Kyocera KC200GT PV module obtained by simulation: (a) under constant temperature and (b) under constant solar radiation.

**Figure 6.** Identification of *Isc, Voc*, *Impp*, *Vmpp* and *Pmpp* on the I-V and P-V curves.
