Tese
Estudo e desenvolvimento de conversores cc-cc com elevado ganho de tensão baseados na topologia do SEPIC isolado
Fecha
2022-12-15Autor
Andres, Bernardo
Institución
Resumen
This Doctoral Thesis makes a detailed study and development of topologies of dc-dc converters
with high voltage gain for photovoltaic microinverters. This requirement is because of low
voltage of photovoltaic module, which has to be suitable for the high voltage of inverter dc bus.
Due to low power of this system, the isolated SEPIC is chosen as standard topology for
synthesis of others converters, because it uses a single semiconductor switch, besides providing
galvanic isolation among photovoltaic module and electrical grid. To solve some problems of
this converter, besides providing a higher static gain, some cells are added to converter and
analyzed. The topologies obtained and defined as most promising and more relevant are
selected to be analyzed with more detailing. The proposed converters are deeply analyzed as to
its operation and equation for operation analysis and definition of voltage and current stress.
All the analyzed converters show a characteristic of resonant operation, which brings the
advantage of soft switching, reducing the switching losses. Besides that, they are capable to
solve some problems of isolated SEPIC, such as the replacement of coupled inductor by the
transformer, besides mitigating voltage spikes on secondary side, and decreasing voltage stress
over some components. Lastly, and not less important, the static gain is significatively
increased, without the excessive addition of components. To validate all the concepts,
assumptions and equations performed, experimental results are presented. These results aim to
verify the compatibility among converters waveforms, besides issues of soft switching, listing
some advantages and disadvantages of each converter, also presenting the efficiency curves and
the loss estimation for each converter. In this way, this work aims to contribute making a
detailed study and developing converters to be used on a photovoltaic microinverter. To affirm
this propose, experimental results are obtained and presented, in order to make a theoreticalexperimental
comparison among topologies of converters, aiming to improve the quality and
trustworthiness of this work.