Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm

Xiaojun Zhao, Chunjiang Zhang*, Xiuhui Chai, Jinlong Zhang, Fanqi Liu, Zhe Zhang

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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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.
Original languageEnglish
JournalJournal of Modern Power Systems and Clean Energy
Volume6
Issue number6
Pages (from-to)1319–1331
ISSN2196-5625
DOIs
Publication statusPublished - 2018

Keywords

  • Unified power quality conditioner (UPQC)
  • Unbalanced loads
  • Matching-ratio compensation
  • Balance control
  • DC bus voltage fluctuations

Cite this

Zhao, Xiaojun ; Zhang, Chunjiang ; Chai, Xiuhui ; Zhang, Jinlong ; Liu, Fanqi ; Zhang, Zhe. / Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm. In: Journal of Modern Power Systems and Clean Energy. 2018 ; Vol. 6, No. 6. pp. 1319–1331 .
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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",
author = "Xiaojun Zhao and Chunjiang Zhang and Xiuhui Chai and Jinlong Zhang and Fanqi Liu and Zhe Zhang",
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Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm. / Zhao, Xiaojun; Zhang, Chunjiang; Chai, Xiuhui; Zhang, Jinlong; Liu, Fanqi; Zhang, Zhe.

In: Journal of Modern Power Systems and Clean Energy, Vol. 6, No. 6, 2018, p. 1319–1331 .

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm

AU - Zhao, Xiaojun

AU - Zhang, Chunjiang

AU - Chai, Xiuhui

AU - Zhang, Jinlong

AU - Liu, Fanqi

AU - Zhang, Zhe

PY - 2018

Y1 - 2018

N2 - 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.

AB - 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.

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KW - Unbalanced loads

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KW - Balance control

KW - DC bus voltage fluctuations

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DO - 10.1007/s40565-018-0383-7

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JO - Journal of Modern Power Systems and Clean Energy

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