Page 339 - A Comprehensive Guide to Solar Energy Systems

344 A CoMPreheNSIVe GuIDe To SolAr eNerGy SySTeMS

FIGURE 16.10 The four fundamental inverter systems suited for maximum power point tracking in residential
installations [1] (A) String inverter, (B) Smart DC–DC optimizers, (C) Differential power processing, and (D) Micro
inverters.

controlled inverter. Although it is a well-tested and simple system, the MPPT process in
this arrangement has higher losses, due to the current–voltage characteristic mismatch of
real PV panels preventing them to operate at their MPP.
By connecting a DC–DC converter to each PV panel as in Fig. 16.10B, it is possible to
control and operate each panel independently. Although smart DC–DC optimizers do not
increase the power rating of the PV panels, it does allow the true MPP of each PV panel to
be tracked in a mismatched string. This is a high cost topology and has reduced conver-
sion efficiency associated with using multiple smaller power converters, which may be
offset by the increase in energy yield due to the higher overall system MPP. This topology
has a potential in residential applications after the development of high temperature and
low cost DC–DC converters using emerging power electronics switching devices.
The topology in Fig. 16.10C is principally the same as the smart DC–DC optimizer
system, but power is instead bypassed around weaker PV panels. Note that to reduce the