Negative-Sequence Current Capability in Low-Capacitance Cascaded H-Bridge Static Compensators With Optimal Third- Harmonic Circulating Current Injection

The cascaded H-bridge (CHB) low-capacitance static compensator (LC-StatCom) has a limited negative-sequence current injection capability compared to a conventional CHB StatCom, due to the comparatively larger oscillations on the capacitor voltages. Placing limits on the ability to provide negative-s...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2023-04, Vol.38 (4), p.4544-4558
Main Authors: Ramos, Ezequiel Rodriguez, Leyva, Ramon, Farivar, Glen G., Townsend, Christopher D., Pou, Josep
Format: Article
Language:English
Subjects:
Automatic voltage control
Capacitance
Capacitance bridges
Capacitors
Cascaded H-bridge (CHB)
circulating current injection
compensation region of negative-sequence currents
Compensators
Current injection
Electric potential
Harmonic analysis
Linear programming
multilevel converter
optimization methods
Oscillators
STATCOM
static compensator (STATCOM)
Steady-state
thin dc capacitor
Unbalance
Voltage
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Summary:The cascaded H-bridge (CHB) low-capacitance static compensator (LC-StatCom) has a limited negative-sequence current injection capability compared to a conventional CHB StatCom, due to the comparatively larger oscillations on the capacitor voltages. Placing limits on the ability to provide negative-sequence current to the grid for a given capacitor size is required to prevent overmodulation. This article shows that these limits can be maximized by injecting an optimal third-harmonic circulating current. The effects of injecting the third-harmonic current on the capacitor voltages, both in balanced and unbalanced grid voltage conditions, are analyzed. Specifically, the procedure allows the knowledge of the potential capability of the LC-StatCom when injecting negative-sequence currents. The procedure is based on a linear programming approach. Although the procedure is applicable to any CHB StatCom, regardless of the submodule capacitor size, it is particularly important in LC-StatComs. To corroborate the proposed analysis, simulation and experimental results under balanced and unbalanced grid voltage conditions are presented.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2022.3233033