An Efficient Single-Sourced Asymmetrical Cascaded Multilevel Inverter With Reduced Leakage Current Suitable for Single-Stage PV Systems

An isolated single sourced multi-output dc/dc converter with a high-frequency link was proposed before to feed different cells of the Asymmetrical Cascaded H-bridge (ACHB) inverter. One of the fundamental advantages of the ACHB is that the main H-bridge is commutated with fundamental frequency, pass...

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Bibliographic Details
Published in:IEEE transactions on energy conversion 2019-03, Vol.34 (1), p.211-220
Main Authors: Ahmed, Ashraf, Sundar Manoharan, Mohana, Park, Joung-Hu
Format: Article
Language:English
Subjects:
ACHB inverter
Electric converters
Electric potential
Energy conversion efficiency
Firing
Firing angle
High voltages
high-frequency link converter
Inverters
Leakage current
Leakage currents
Maximum power tracking
Modulation
Power rating
programmable firing angles
Resonant frequencies
SISO (control systems)
Switches
Switching
THD minimization
Topology
Voltage control
Voltage converters (DC to DC)
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Description
Summary:An isolated single sourced multi-output dc/dc converter with a high-frequency link was proposed before to feed different cells of the Asymmetrical Cascaded H-bridge (ACHB) inverter. One of the fundamental advantages of the ACHB is that the main H-bridge is commutated with fundamental frequency, passing the majority of the inverter power. However, the isolated dc/dc converter needs to be connected to the main voltage source with high-voltage/high-frequency switches, which limits the power capability and the efficiency of the converter. In this paper, a switching pattern based on nearest level modulation method is proposed to command all the power to be transferred through the main H-bridge. Therefore, the power circulates between the auxiliary H-bridges with no need for high-voltage switches. As a result, a single-input single-output auxiliary converter is needed with only 5% of the power rating. This solution reduces cost and size while it improves the efficiency of the converter. Furthermore, the architecture makes the inverter more suitable for high power and high-voltage applications. The inverter switching strategy is based on programmable firing angles. The main dc-link of the grid connected inverter is controlled to achieve maximum power point tracking, while the dc/dc isolated converter is controlled to regulate the auxiliary dc-links. The proposed topology is verified by simulation and experimental results using a 1.5 kW hardware prototype.
ISSN:0885-8969
1558-0059
DOI:10.1109/TEC.2018.2874076