**4. Conclusion**

The tracking method validation was achieved plotting the PV operating point on the I-V plan during temperature and solar radiation changes, as is illustrated in Figure 22. For reaching this result a scope on XY mode, where X refers to the PV output voltage and Y re‐

**Figure 22.** Experimental PV operating point on I-V plan during temperature and solar radiation changes. Scope on XY

**Figure 23.** Theoretical MPP trajectory for solar radiation and temperature measured during experimental evaluation.

In order to prove that the obtained experimental trajectory coincides with the MPP, the val‐ ues of solar radiation and temperature were also collected by a data logger and summarized by Table 8. The measurements were achieved on middle of April in the Florianopolis Island

.

fers to the PV output current, was employed.

mode (X-voltage, Y-current)

110 Sustainable Energy - Recent Studies

– south of Brazil – located at latitude 27o

Currently the most common employed PV tracking algorithm are Perturb and Observe and Incremental Conductance. Perturb and observe is simple, however it failures to track the MPP under abrupt changes on solar radiation and presents oscillations around the MPP on steady-state. Incremental conductance is accurate, however, it implementation is more com‐ plex. In these both algorithms, it is necessary to measure the PV output voltage and current.

The proposed algorithm is simpler than perturb and observe and more accurate than the in‐ cremental conductance. Furthermore, the current sensor is substituted by a temperature sen‐ sor, implying in cost reduction. Eliminating the current sensor means avoid the output power high frequency variation associated to the PV current (directly proportional to solar radiation), thus, there is no oscillation around the MPP. Since the tracking is based on the temperature, its low dynamic ensures a soft tracking, but accurate and fast.

Based on the exposed, this tracking method employment allows a significant improvement on the PV operation. Note that in PV generation the power losses may be separated in two terms: the first one is associated to the power converters efficiency and the second to the tracking algorithm efficiency. Thus, if an optimized tracking algorithm is employed, the global efficiency is increased.

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

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From the dc-dc analysis it was verified that buck and boost converters, even been largely applied for tracking applications, are not proper for this proposal, since they can track the MPP only in a part of the I-V plan. On the other hand, buck-boost converter (and Cuk, SEP‐ IC or zeta) may track the MPP around the whole I-V plan, configuring the better option for tracking applications.

Finally, an optimized tracking system only is obtained if both, dc-dc converter and tracking algorithm properly operate. This condition is accomplished when a buck-boost converter is employed in combination with the MPP-temp tracking method.
