Capacitor Voltage Balancing for Neutral Point Clamped Dual Active Bridge Converters

A capacitor voltage balancing method is proposed for a full-bridge neutral point diode clamped (NPC) dual-active bridge (DAB) converter. In existing literature, capacitor voltage balancing is achieved by actively selecting between the small voltage vectors, i.e., connecting either the upper or the l...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2020-10, Vol.35 (10), p.11267-11276
Main Authors: Awal, M. A., Bipu, Md Rashed Hassan, Montes, Oscar Andres, Feng, Hao, Husain, Iqbal, Yu, Wensong, Lukic, Srdjan
Format: Article
Language:English
Subjects:
Balancing
Bridge circuits
Capacitor voltage balancing
Capacitors
Clamping
Data buses
dual active bridge (DAB)
Electric bridges
Electric converters
Electrical measurement
ENGINEERING
Legged locomotion
neutral point balancing
neutral point diode clamped (NPC)
Offsets
Power flow
Switches
Topology
Transformers
Voltage control
Voltage measurement
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Summary:A capacitor voltage balancing method is proposed for a full-bridge neutral point diode clamped (NPC) dual-active bridge (DAB) converter. In existing literature, capacitor voltage balancing is achieved by actively selecting between the small voltage vectors, i.e., connecting either the upper or the lower capacitor on the dc bus to the transformer winding, on the basis of measured voltage mismatch. These balancing methods are dependent on the direction of power flow through the DAB converter. In this work, we propose a voltage balancing controller, which is independent of power flow direction and does not require adjustments of active voltage vectors through the modulator. Irrespective of the direction of transformer current, by dynamically shifting the switching instants of the inner switch pairs in the two NPC legs during the free-wheeling/zero voltage vector time, either of the two capacitors can be selectively charged without introducing any offsets in the voltage-second seen by the transformer. A simple bidirectional phase-shift modulator is designed to facilitate voltage balancing irrespective of power flow direction or mode of operation. The proposed method is highly and universally effective under any converter operating condition and was verified and demonstrated through analysis, simulation, and hardware experiments using a laboratory prototype.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2020.2988272