Coupling Effect Reduction of a Voltage-Balancing Controller in Single-Phase Cascaded Multilevel Converters

This paper presents a new voltage-balancing controller for cascaded multilevel converters, especially for single-phase cascaded multilevel converters. It proposes a control algorithm that devotes itself not only to balancing the floating dc capacitors but also to eliminating the coupling effect betw...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2012-08, Vol.27 (8), p.3530-3543
Main Authors: Xu She, Huang, Alex Q., Tiefu Zhao, Gangyao Wang
Format: Article
Language:English
Subjects:
Applied sciences
Capacitors
Cascaded multilevel converter
Circuit properties
Control systems
Controllers
Convertors
Couplings
decoupling control
Electric power
Electric, optical and optoelectronic circuits
Electrical engineering. Electrical power engineering
Electrical equipment
Electrical machines
Electronic circuits
Electronics
Exact sciences and technology
Modulation
Power electronics, power supplies
Reactive power
Rectifiers
Regulation and control
Signal convertors
Simulation
single-phase d-q control
voltage balance
Voltage control
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Summary:This paper presents a new voltage-balancing controller for cascaded multilevel converters, especially for single-phase cascaded multilevel converters. It proposes a control algorithm that devotes itself not only to balancing the floating dc capacitors but also to eliminating the coupling effect between the voltage-balancing controller and the original system controller (controller without additional voltage-balancing controllers). Specifically, the average model in the d-q coordinate frame is derived and the control law is established. Then, the coupling effect between the voltage-balancing controller and the original system controller is identified and a new expression for duty cycle modification is proposed thus to eliminate the effect. Furthermore, this paper gives the design considerations of the pro- posed method, including the derivation of key transfer functions and effective voltage-balancing area, for the completeness of the discussion. Moreover, the reference generation techniques of the voltage-balancing controller are also discussed. This paper investigates the voltage imbalance in the soft-start process caused by an unsuitable reference, and presents a simple modified reference generation solution. Finally, both simulation and experimental results verify the performance of the proposed control system.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2012.2186615