This paper investigates the modern topology of multilevel converters, which are suitable for use in high power photovoltaic applications with the focus on achieving lower total harmonic distortion and better efficiency. Multilevel converters offer several advantages compared to conventional types. Multilevel converters provide high quality output while using the low switching frequency. It affects the switching losses, size of semiconductor switches and harmonic filters. This research investigates various topologies of multilevel converter for high power photovoltaic applications and compares their THD, efficiency, number of required semiconductors and other important characteristics. All topologies are simulated using MATLAB/Simulink in the same operating conditions. Finally, the more suitable multilevel topology is selected with respect to the simulation results.
- Multilevel converter
- Qualitative study
- High power application
Fig 1: a) NPC b) Capacitor clamped c) Cascade d) Z-source e) Quasi Z-source f) Hybrid
EXPECTED SIMULATION RESULTS:
Fig.2. Three level NPC inverter voltage and current waveforms.
Fig. 3. Three level Capacitor clamped voltage and current waveforms.
Fig. 4. Voltage and current waveforms of three level cascaded inverter.
Fig.5. Voltage and current waveforms of three level Z source inverter.
Fig.6. Voltage and current waveforms of three level Quasi Z source.
Fig. 7. Voltage and current waveforms of three level hybrid model.
The price analysis of the converter shows that multilevel converters are more economic than conventional types in the case of medium and high power applications. In This research, different multilevel converter topologies have been investigated and compared in order to find the most suitable topology, which is appropriate to use in the PV applications. Six multilevel topologies, which were proposed in the literature, have been investigated. The investigation was done via quantitative and qualitative study. In quantitative study, important output parameters of proposed multilevel topologies were evaluated using Matlab/Simulink at the same operating point. Also, a qualitative analysis has been performed to investigate some advantages and disadvantages of each topology, which cannot be considered in the simulation. The results prove that quasi Z-source converter has better performance in comparison with other types.
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