ABSTRACT:
This paper presents a switched-capacitor multilevel
inverter (SCMLI) combined with multiple asymmetric DC sources. The main
advantage of proposed inverter with similar cascaded MLIs is reducing the
number of isolated DC sources and replacing them with capacitors. A
self-balanced asymmetrical charging pattern is introduced in order to boost the
voltage and create more voltage levels. Number of circuit components such as
active switches, diodes, capacitors, drivers and DC sources reduces in proposed
structure. This multi-stage hybrid MLI increases the total voltage of used DC
sources by multiple charging of the capacitors stage by stage. A bipolar output
voltage can be inherently achieved in this structure without using single phase
H-bridge inverter which was used in traditional SCMLIs to generate negative
voltage levels. This eliminates requirements of high voltage rating elements to
achieve negative voltage levels. A 55-level step-up output voltage (27 positive
levels, a zero level and 27 negative levels) are achieved by a 3-stage system
which uses only 3 asymmetrical DC sources (with amplitude of 1Vin, 2Vin and
3Vin) and 7 capacitors (self-balanced as multiples of 1Vin). MATLAB/SIMULINK
simulation results and experimental tests are given to validate the performance
of proposed circuit.
KEYWORDS:
1.
Multi-level
inverter
2.
Switched-capacitor
3.
Bipolar
converter
4.
Asymmetrical
5.
Self-balancing
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig
(1) Three stage structure of the proposed inverter
EXPECTED SIMULATION RESULTS:
Fig
(2) Waveform of the output voltage in (a) 50Hz and pure resistive load (b)
the
inset graphs of voltage and current
Fig
(3) waveform of the output voltage in 50Hz with resistive-inductive load
Fig
(4) Capacitor’s voltage in 50Hz (a) middle stage (b) last stage
CONCLUSION:
In
this paper, a multilevel inverter based on combination of multiple DC sources
and switched-capacitors is presented. Unlike traditional converters which used
H-bridge cell to produce negative voltage that the switches should withstand
maximum output AC voltage, the suggested structure has the ability of
generating bipolar voltage (positive, zero and negative), inherently. Operating
principle of the proposed SCMLI in charging and discharging is carried out.
Also, evaluation of reliability has been done and because of high number of
redundancy, there has been many alternative switching states which help the
proposed structure operate correctly even in fault conditions. For confirming
the superiority than others, a comprehensive comparison in case of number of
devices and efficiency is carried out and shows that the proposed topology has
better performance than others. For validating the performance, simulation and
experimental results are brought under introduced offline PWM control method.
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[3]
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[4]
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