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.
REFERENCES:
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[4] K. K. Gupta, A. Ranjan, P. Bhatnagar, L. K. Sahu, and S. Jain, "Multilevel inverter topologies with reduced device count: A review," IEEE transactions on power electronics, vol. 31, pp. 135-151, 2015.
[5]
P. Omer, J. Kumar, and B. S. Surjan, "A Review on Reduced Switch Count
Multilevel Inverter Topologies," IEEE Access, vol. 8, pp.
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