A
Dissertation for the Degree of Doctor of Philosophy
Power Quality Improvement of Single-Phase
Grid-Connected
Photovoltaic Inverter
Department
of Information and Communications Engineering
Graduate School
Chungnam
National University
By
Trung-Kien Vu
Advisor
|
Se-Jin Seong
|
February 2011
ABSTRACT*
The economical and environmental impacts of fossil fuels have
forced society to investigate
sustainable solutions. The interest
has
focused on the
renewable energy sources since the green and clean benefits. Consequently,
investments in research and development in the field of power electronics have
increased proportionally, especially in high voltage and high power
grid-connected systems.
The distributed power generation (DG) systems are becoming more
common as the need for electric power
increases because of taking advantage
of using different energy sources such as wind and solar. A few examples are
hybrid cars, solar houses or hospitals in remote areas
where providing clean,
efficient and reliable
electric power is critical to the loads. In such systems, the power is
distributed from the source side to the load side via power electronic
converters in the system. At low and medium power applications, the task is
often left to single-phase inverters where they are the only interface between
sources connected to dc bus and loads connected to an ac bus. This dissertation
investigates the power quality improvements to properly regulate the
power flow between renewable source
and the utility network. The control method for
single-phase inverters used in low and medium power DG systems is based on (and
also takes the advantage of) the well-known d-q transformation (which is mostly
employed for three-phase converters’ analysis
and control design).
The transformation requires at least two independent phases for each
state variable in the system; thus a second phase must be created. This virtual-phase can be done by
DSP implementation, hence there is no need for additional hardware in the
system, making it more attractive and cost effective method.
The
Proportional-Resonant (PR) controller based current control scheme, compared
with conventional Proportional-Integral (PI)
controller, not only provides a
superior transient response but also provides a zero steady-state error as well
as a high disturbance rejection and a low output current THD under grid-tie
mode operation. The entire controller can be implemented in a DSP digital
control board
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