DOI:10.1007/s40565-018-0383-7 |
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Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm |
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Author:
Xiaojun ZHAO1, Chunjiang ZHANG1, Xiuhui CHAI1, Jinlong ZHANG1, Fanqi LIU1, Zhe ZHANG2
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Author Affiliation:
1. Department of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China
2. Department of Electrical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
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Foundation: |
This work was supported by National Natural
Science Foundation of China (No. 51477148). |
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Abstract: |
In three-phase four-wire systems, unbalanced
loads can cause grid currents to be unbalanced, and this
may cause the neutral point potential on the grid side to
shift. The neutral point potential shift will worsen the
control precision as well as the performance of the threephase
four-wire unified power quality conditioner (UPQC),
and it also leads to unbalanced three-phase output voltage,
even causing damage to electric equipment. To deal with
unbalanced loads, this paper proposes a matching-ratio
compensation algorithm (MCA) for the fundamental active
component of load currents, and by employing this MCA,
balanced three-phase grid currents can be realized under
100% unbalanced loads. The steady-state fluctuation and
the transient drop of the DC bus voltage can also be
restrained. This paper establishes the mathematical model
of the UPQC, analyzes the mechanism of the DC bus
voltage fluctuations, and elaborates the interaction between
unbalanced grid currents and DC bus voltage fluctuations;
two control strategies of UPQC under three-phase stationary
coordinate based on the MCA are given, and
finally, the feasibility and effectiveness of the proposed
control strategy are verified by experiment results. |
Keywords: |
Unified power quality conditioner (UPQC),
Unbalanced loads, Matching-ratio compensation, Balance
control, DC bus voltage fluctuations |
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Online Time:2018/11/11 |
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