Droop control has commonly been used with distributed generators
for relating their terminal parameters with power generation. The generators
have also been assumed to have enough capacities for supplying the required
power. This is however not always true, especially with renewable sources
with no or insufficient storage for cushioning climatic changes. In addition,
most droop-controlled literatures have assumed a single dc-ac inverter with
its input dc source fixed. Front-end dc-dc converter added to a two-stage
photovoltaic (PV) system has therefore usually been ignored. To address these
unresolved issues, an improved droop scheme for a two-stage PV system has
been developed in the paper. The Proposed scheme uses the STATCOM
control structure in both grid-connected and islanded modes, which together
with properly tuned synchronizers, and mitigates the harmonics, by providing
Reactive power and Load current Subsequently the proposed scheme adapts
well with internal PV and external grid fluctuations, and is hence more
precise with its tracking, as compared with the traditional droop scheme.
Simulation and experimental results are obtained using MATLAB Simulink.
Keywords: Droop Control, Photovoltaic, STATCOM.
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