ABSTRACT:
A novel multilevel inverter based on a
three-level half bridge is proposed for the DC/AC applications. For each power
cell, only one DC power source is needed and five-level output AC voltage is
realized. The inverter consists of two parts, the three-level half bridge, and
the voltage vector selector, and each part consists of the four MOSFETs. Both
positive and negative voltage levels are generated at the output, thus, no
extra H-bridges are needed. The switches of the three-level half bridge are
connected in series, and the output voltages are (Vo, Vo/2, and
0). The voltage vector selector is used to output minus voltages (Vo
and Vo/2) by different conducting states. With
complementary working models, the voltages of the two input capacitors are
balanced. Besides, the power cell is able to be cascaded for more voltage
levels and for higher power purpose. The control algorithm and two output
strategies adopted in the proposed inverter are introduced, and the
effectiveness is verified by simulation and experimental results.
KEYWORDS:
1. Bridge
circuits
2. DC-AC
power converters
3. Modular
multilevel converters
4. Pulse
width modulation converters
5. Voltage
control
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Figure 1. The proposed hybrid ZVS
bidirectional DC/AC inverter topology.
EXPERIMENTAL RESULTS:
Figure 2. Waveforms with LFF strategy.
Figure 3. Waveforms with HFSPWM strategy.
Figure 4. Voltages of input capacitors C1 and C2.
Figure 5. Output waveforms of 2-level cascaded
topologies.
CONCLUSION:
A novel multilevel inverter based on a
three-level half bridge is proposed for DC/AC applications in this paper. For
each power cell, only one DC power source is needed and 5-level output AC
voltage is realized. Both positive and negative voltage levels are generated at
the output, thus no extra H bridges are needed. The non-isolated topology
(transformerless) eliminates magnetic losses. The operating principle and the
working stages of the proposed inverter are introduced, while the two output
strategies are discussed in detail. Besides, voltage balance strategy is
adopted to balance the bus capacitor voltages, and stage optimization method is
applied to further reduce the switching losses. Finally, a simulation is
carried out to verify the two output strategies, voltage balance strategy and
the cascaded ability, and a laboratorial experiment is carried out to test the
THD losses and the total efficiency.
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