Improvement of Voltage Unbalance by Current Injection Based on Unbalanced Line Impedance in Distribution Network with PV System

Daisuke Iioka, Takahiro Fujii, Toshio Tanaka, Tsuyoshi Harimoto, Junpei Motoyama and Daisuke Nagae
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Daisuke Iioka: Department of Electrical and Electronic Engineering, College of Engineering, Chubu University, Kasugai 487-8501, Japan
Takahiro Fujii: Department of Electrical Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
Toshio Tanaka: Kyushu Electric Power Co., Inc., Fukuoka 815-8720, Japan
Tsuyoshi Harimoto: Kyushu Electric Power Co., Inc., Fukuoka 815-8720, Japan
Junpei Motoyama: Kyushu Electric Power Transmission and Distribution Co., Inc., Fukuoka 810-0004, Japan
Daisuke Nagae: Kyushu Electric Power Transmission and Distribution Co., Inc., Fukuoka 810-0004, Japan

Energies, 2021, vol. 14, issue 23, 1-16

Abstract: In this study, we have proposed a novel current injection determination method that improves the voltage unbalance based on the unbalanced line impedance in a distribution network with a large-capacity PV system. An increase in the unbalance of the distribution line voltage was observed owing to a large-scale reverse power flow. To visualize this phenomenon, the P-V curves were derived for each phase to indicate the increase in the voltage unbalance with respect to the reverse power flow. Based on the derived P-V curves, the effect of a current unbalance on the voltage unbalance was investigated. It was clarified that there is a current unbalance that can improve the voltage unbalance even if the line impedance is unbalanced. In other words, the current unbalance that can theoretically make the voltage unbalance zero could be expressed in terms of the symmetrical components of unbalanced line impedance. As an application of the proposed method, the effect of the mitigation of voltage unbalance was demonstrated by controlling single-phase reactors, whose numbers were determined by using the relationship between the unbalanced line current and unbalanced line impedance.

Keywords: distributed power generation; photovoltaic systems; power quality; power distribution; power system analysis computing; power system measurements; reverse power flow; voltage unbalance (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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