ABSTRACT:
Voltage-source
inverter has been used widely in traditional photovoltaic systems which have
limitations. To overcome, Z-source inverter has been introduced. In spite of
all the features introduced in Z-source inverter, its configuration has been improved
over the years, like trans-Z-source inverter which has added advantages
compared to traditional inverters, namely buck–boost feature, lesser passive
elements, and higher voltage boost gain. In this paper, photovoltaic arrays are
connected to the grid via the trans-Z-source inverter with the aim of improving
its power quality. Moreover, the shoot through duty ratio is kept constant in
the switching control method to add features like lower voltage stress (higher reliability),
lower total harmonic distortion (lower maintenance cost), and higher voltage boost
ratio. To evaluate the precision of the proposed system, the photovoltaic
system is simulated on a standard grid and under partial shading condition
which brings about voltage sag, and hence, a dynamic voltage restorer is used
to mitigate voltage sag. Simulation results are presented to verify the
validation of the proposed photovoltaic system in terms of voltage and current
THD reducing 78.2% and 19.7%, respectively.
KEYWORDS:
1. PV system
2. Trans-Z-source inverter
3. THD
4. Partial shading
5. Voltage sag
6. DVR
SOFTWARE:
MATLAB/SIMULINK
CONCLUSION:
In
this paper, a PV system is connected to the IEEE 15-bus test network via
trans-ZSI with the aim of power quality improvement, plus MCBC control is used
to decrease voltage and current THD, and more importantly, to reduce voltage
stress across the switches. The results indicate that applying the trans-ZSI
and an appropriate switching method improve the power quality of the PV system
to a considerable extent. Besides, the cost, volume, and weight of this
inverter are low because of having no low-frequency ripples of the output
voltage. What is more, as the shoot through does not damage the inverter, the
reliability of the inverter is higher. In turn, not only is the reliability of
this inverter higher, but also its maintenance cost is lower. The proposed PV
system is also studied under partial shading conditions to validate its
performance when there are some voltage sags. So, a DVR is employed to detect voltage
sags and then mitigate them once partial shading happens. Two conclusions can
be drawn from cases C and D: The voltage amplitude is roughly fallen back to
its rated value, and the voltage THD is reduced when trans-ZSI is used. To
summarize, the results illustrate that the PV system operates accurately with
the trans-ZSI, as opposed to the PV systems with traditional VSI.
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