A Method for Solving Current Unbalance Problem of Paralleled Single-Phase Grid-Connected Unipolar-PWM Inverters With Common Dc Bus

Unipolar-pulsewidth modulation (UP-PWM) inverter takes advantages of high power efficiency and small output chokes which is widely used in the industry. However, UP-PWM inverters cannot be used in parallel operation due to a current unbalance problem. This paper studies the current unbalance problem...

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Bibliographic Details
Published in:IEEE transactions on industry applications 2019-11, Vol.55 (6), p.7595-7603
Main Authors: Li, Dong, Ho, Carl Ngai Man, Siu, Ken King Man
Format: Article
Language:English
Subjects:
Balancing
Circulating current
Converters
Data buses
Energy conversion efficiency
Inductors
Inverters
Parallel operation
Power efficiency
Pulse duration modulation
Pulse width modulation
Switches
Topology
Unbalance
unbalanced current
unipolar pulsewidth modulation (UP-PWM)
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Summary:Unipolar-pulsewidth modulation (UP-PWM) inverter takes advantages of high power efficiency and small output chokes which is widely used in the industry. However, UP-PWM inverters cannot be used in parallel operation due to a current unbalance problem. This paper studies the current unbalance problem of paralleled UP-PWM inverters with common dc bus and ac bus. First, the problem of unbalanced inductor current is defined and analyzed. Second, a technique to eliminate unbalanced currents is proposed. The proposed current balancing technique only requires one more current sensor in an inverter module rather than changing converter topology or modulation method, which makes it possible to apply UP-PWM inverters in parallel-operation while keeping the advantages of unipolar switching. The proposed current balancing method is verified by both simulation and hardware experiment. Experimental verification is performed on two 1 kW, 400 V input, and 120 V/60 Hz output prototypes, which shows a good agreement to the analytical study.
ISSN:0093-9994
1939-9367
DOI:10.1109/TIA.2019.2921709