Page 337 - A Comprehensive Guide to Solar Energy Systems

342 A CoMPreheNSIVe GuIDe To SolAr eNerGy SySTeMS

FIGURE 16.8 The decentralized cascaded multilevel modular integrated converters inverter system.

knowledge of its own DC-link voltage and current (for MPPT), its grid current (for injecting
grid power) and its grid voltage (zero-crossing synchronization). Connecting the MICs in
cascade requires three primary connections:

• The outputs of each MIC are connected in series (through their filters) to the grid.
• Each MIC has a separate grid connection for measurement purposes.
• Each MIC has a communication link to the neighboring MIC which may occur
through power line communications (PlC), an additional wired link, or through a
wireless connection (Blue tooth, Wi-fi, etc.).

16.3.3.2 Grid-Connected Current Source Inverter With Feed Forward Control [3]
A simple and low-cost single-phase current-sourced grid-connected inverter topology is
given in Fig. 16.9. The topology (which has been used in wind generators previously) con-
sists of a sinusoidally modulated boost switch (switched mode rectifier based) and line-
frequency commutated unfolding circuit accommodating thyristor switches. The control
algorithm adjusts the modulation index of the boost switch to control the inverter output
current hence the output power. As a result of the significant losses in the DC link induc-
tor, (due to the copper and iron) pulse area modulation can be used to reduce the size of
the inductor. This modulation approach is similar to feed-forward compensation control.
The topology has the potential to offer a low cost, simple, and reliable solution to reduce
inductor and switch losses.