Modulation for Cascaded Multilevel Converters in PV Applications With High Input Power Imbalance

Cascaded multilevel inverters, such as the cascaded H-bridge (CHB) converter, are an attractive solution for multistring photovoltaic (PV) systems, because they enable direct connection to the medium voltage grid and maximum power point tracking (MPPT) of multiple strings. As a challenge of the topo...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2021-09, Vol.36 (9), p.10866-10878
Main Authors: Ko, Youngjong, Andresen, Markus, Wang, Kangan, Liserre, Marco
Format: Article
Language:English
Subjects:
Cascaded H-Bridge (CHB)
Computer architecture
Converters
discontinuous modulation
Energy conversion efficiency
Inverters
Maximum power tracking
Microprocessors
Modulation
module mismatch
multistring architecture
Phase modulation
photovoltaic (PV)
Photovoltaic cells
power imbalance
Power quality
Reactive power
Strings
Topology
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Summary:Cascaded multilevel inverters, such as the cascaded H-bridge (CHB) converter, are an attractive solution for multistring photovoltaic (PV) systems, because they enable direct connection to the medium voltage grid and maximum power point tracking (MPPT) of multiple strings. As a challenge of the topology, the operation with high power imbalance in the strings is constrained by the overmodulation. This limitation is analyzed for sinusoidal modulation and the impact on the maximum power imbalance is demonstrated. For increasing the operating range with maximum power tracking in the strings, a discontinuous modulation with extended maximum power imbalance and reduced losses is proposed. The method is analyzed in terms of maximum power imbalance, efficiency and power quality. In addition, the method is validated on an experimental test bench.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2021.3065028