ABSTRACT:
A
multi-cell hybrid 21-Level multilevel inverter is proposed in this paper. The
proposed topology includes two-unit; an H-bridge is cascaded with a modified
K-type unit to generate an output voltage waveform with 21 levels based only on
two unequal DC suppliers. The proposed topology's advantage lies in the fine
and clear output voltage waveforms with high output efficiency. Meanwhile, the
high number of output voltage waveform levels generates a low level of
distortion and reduces the level of an electromagnetic interface (EMI).
Moreover, it reduces the voltage stress on the switching devices and gives it a
long lifetime. Also, the reduction in the number of components has a noticeable
role in saving size and cost. Regarding the capacitors charging, the proposed
topology presents an online method for charging and balancing the capacitor's
voltage without any auxiliary circuits. The proposed topology can upgrade to a
high number of output steps through the cascading connection. Undoubtedly this
cascading will increase the power level to medium and high levels and reduce
the harmonics content to a neglectable rate. The proposed system has been
tested through the simulation results, and an experimental prototype based on
the controller dSPACE (DS-1103) hardware unit used to support the simulation
results.
KEYWORDS:
1. 21-Level
Multilevel Inverter (MLI)
2. Hybridization
3. Modified
K-type inverter
4. Online
charging
5. Self-balancing
6. Voltage
boosting inverter
7. Total
Harmonic Distortion (THD)
SOFTWARE: MATLAB/SIMULINK
CONCLUSION:
The work in this paper presented a
hybrid multilevel inverter that consisted of a series connection between two
units (an HB unit with a modified K-Type unit). This combination generates an
output voltage waveform with 21 steps. This high number steps in the output
voltage help in reducing the level of noises in the output voltage and reduced
the stress in the switching devices, which on the one hand generating fine and
clear waveforms and on the other hand reduces the harmonic content in the
waveforms to a deficient level (satisfying the harmonics standard IEEE519).
Economically, the structure of the proposed topology presented an optimal
design in terms of reducing the number of switches and DC sources which in turn
enhancing the system reliability by reducing the inverter cost. For the
capacitors charging process, the paper presents an online method for charging
and balancing the capacitor voltages without any auxiliary circuits for that.
This helps in the continuous operation of the charging and discharging process
for the capacitor without disturbing the process of generating the output
voltage. The proposed topology supports the modularity process in order to
maximize the range of output power to the medium and high level, and the paper
presented two scenarios for the series connection 2HB+K and HB+2K both the
cases raise the level of the output power and enhances the system performance
to achieve high efficiency. Due to the dependence on multi DC sources, this
topology is suitable for renewable energy applications; DC sources are
abundant. The hybrid renewable energy sources application will be more
appropriate between all the renewable energy applications because the proposed
topology-based mainly on two unequal DC suppliers, which will be available
easily in the hybrid renewable energy sources.
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