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3. Necessity of Joint Adoption of Distributed Maximum Power Point 195

with respect to that one obtained by considering LSCPVUs, is a complicated func-
tion of the operating point. It would be nearly impossible to exactly consider it in the
analytical evaluation of the estimate of the optimal R b . A very important, funda-
mental aspect is the following one: the exact and the approximate PeV characteris-
tics of the strings of LSCPVUs are nearly coincident, in the region of the optimal R b ,
where the highest accuracy is necessary. The greatest errors are localized instead in
the regions of minor interest, from the point of view of the energetic efficiency of the
whole PV system.

3.2.3 Numerical Simulations Concerning Hybrid Maximum Power Point
Tracking Techniques
In this section, the performances of the HMPPTF strategy are compared with those
of HMPPTS by analyzing two different mismatching scenarios (CASE I and CASE
II). The time-domain numerical simulations have been carried out in PSIM environ-
ment; PSIM is a well-known simulation environment for power conversion and con-
trol. The simulated system is represented by a grid-connected PV system composed
of an H-bridge central inverter fed by an array of LSCPVUs adopting boost con-
verters with synchronous rectification (Fig. 5.16).
Fig. 5.16A refers to HMPPTF technique, instead Fig. 5.16B refers to HMPPTS
technique. The substantial differences between the two architectures shown in
Fig. 5.16A and B are linked to the fact that in the case of HMPPTF (Fig. 5.16A)
the DMPPT and CMPPT controllers must be able to exchange useful data to imple-
ment the FEMPV algorithm. In particular, the DMPPT controllers must be able to
provide the values of I SCk (k ¼ 1, 2, ., N) to the CMPPT controller. In fact, such
values are needed to evaluate the approximate PeV equivalent characteristic of
the string of LSCPVUs. On the other hand, the CMPPT controller must in turn be
able to provide the calculated values of v pk (k ¼ 1, 2, ., N) to the DMPPT control-
lers. Such controllers carry out an MP&O technique with starting conditions v pk
(k ¼ 1, 2, ., 11) obtained, as discussed above, by means of the FEMPV algorithm.
As concerns the HMPPTS technique (Fig. 5.16B), the DMPPT and CMPPT control-
lers are independent of one another.

3.2.3.1 Case I
Case I refers to the following set of values: irradiance distribution S ¼ [1000 1000
2
1000 1000 1000 1000 1000 200 200 200 200] W/m ,T ambient ¼ 25 C. Both the

HMPPTS strategy and the HMPPTF strategy adopt the MP&O algorithm as DMPPT
technique. The MP&O parameters of the HMPPTS and HMPPTF techniques are re-
ported in the Table 5.2.
The two parameters T a and Dv pan ref of the MP&O technique (Table 5.2)have been
chosen on the basis of the guidelines provided in [1] by assuming that the maximum
2
rate of change of irradiance level to track without errors is equal to 100 W/(s m ). As
shown in Table 5.2, the main difference between the two DMPPT techniques is rep-
resented by the adopted value of V out lim . In the case of HMPPTS, the value of V out lim
must fulfill the inequalities of Eqs. (5.11) and (5.12), which are valid whenever the