---
title: 2016_An Automated Impedance Estimation Method in Low-Voltage Distribution Network for Coordinated Voltage Regulation
tags: 
author: [小平　大輔](https://convert.docswell.com/user/daisuke-kodaira)
site: [Docswell](https://www.docswell.com/)
thumbnail: https://bcdn.docswell.com/page/V8JDPRWNJG.jpg?width=480
description: S. Han, D. Kodaira, S. Han, B. Kwon, Y. Hasegawa and H. Aki, &quot;An Automated Impedance Estimation Method in Low-Voltage Distribution Network for Coordinated Voltage Regulation,&quot; in IEEE Transactions on Smart Grid, vol. 7, no. 2, pp. 1012-1020, March 2016, doi: 10.1109/TSG.2015.2489199.
published: March 31, 22
canonical: https://convert.docswell.com/s/daisuke-kodaira/K21N4Z-2022-03-31-094237
---
# Page. 1

![Page Image](https://bcdn.docswell.com/page/V8JDPRWNJG.jpg)

1
An Automated Impedance Estimation
Method in Low-Voltage Distribution Network
for Coordinated Voltage Regulation
Sekyung Han, Daisuke Kodaira, Soohee Han, Bokyu Kwon, Yasuo Hasegawa &amp; Hirohisa Aki
Daisuke Kodaira


# Page. 2

![Page Image](https://bcdn.docswell.com/page/4VEPNW9N78.jpg)

Problem: Voltage violation
HV line (22.9 kV)
LV line (220 V)
Normal Power Flow
1
Fixed Voltage due
to the transformer
10
2
9
3
4
5
8
7
6
Reverse Power Flow
Voltage
Voltage upper limit
Voltage lower limit
1
House #
10


# Page. 3

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3
Objective
Voltage regulation requires line impedance, however, which is not recognized.
?
?
?
NODE 3
?
?
NODE 2
NODE 1
• Why impedance have not been recognized so far?
Without DERs on the network, accurate impedance is not necessary;
because there is no requirement for voltage regulation.
Objective
Impedance estimation for voltage regulation


# Page. 4

![Page Image](https://bcdn.docswell.com/page/Z5JGQ5GWEL.jpg)

User A
𝑍𝐴𝐵 ?
User B
𝑉𝐴 ∶ 50~60𝐻𝑧
User C
Voltage
Constraints
𝑉𝐶 , 𝐼𝐶 , 𝑃𝐶
𝑉𝐶 , 𝐼𝐶 , PC
𝑉𝐵 , 𝐼𝐵 , 𝑃𝐵
𝑉𝐴 , 𝐼𝐴 , 𝑃𝐴
𝑉𝐵 , 𝐼𝐵 , 𝑃𝐵
Time
Frequency = 1/50 =0.02[sec]
Required sampling rate
= 0.02/2 = 0.01[sec]
𝑉𝐴 , 𝐼𝐴 , 𝑃𝐴
Smart Meter
（Meter metrology
+ communication
module）
Measured values
are shared
Measuring data including the
phase difference between several points
needs sophisticated GPS system
Constraint:
Estimate impedance without phase difference information
4


# Page. 5

![Page Image](https://bcdn.docswell.com/page/V47QKZXQ7P.jpg)

Model
J-node 5
=
ZJ45
Z 𝑇5
ZT4
ZT3
T-node 5
T-node 4
𝑆𝑇5
𝑆𝑇4
𝑉𝑇5 , 𝐼𝑇5
𝑉𝑇4 , 𝐼𝑇4
J-node 3
ZJ34
J-node 2
ZJ23
ZT2
ZT1
T-node 1
𝑆𝑇3
T-node 2
𝑆𝑇2
𝑉𝑇3 , 𝐼𝑇3
𝑉𝑇2 , 𝐼𝑇2
𝑉𝑇1 , 𝐼𝑇1
T-node 3
J-node 1
ZJ12
Pole-trans
T-node indicates
a household
J-node 4
𝑆𝑇1
• The power (S), voltage (V), and current (I) are measured at each node
• Impedance are estimated based on circuit theory principle. Voltage of J-node 5
can be described in the two ways:
1. 𝑉𝐽5 = 𝑉𝑇5 + 𝑍𝑇5𝐼𝑇5
2. 𝑉𝐽5 = 𝑉𝑇4 + 𝑍𝑇4𝐼𝑇4
Both equations should be equal
∴ 𝑂𝑏𝑗𝑒𝑐𝑡𝑖𝑣𝑒 𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛: 𝑉𝑇5 +𝑍𝑇5𝐼𝑇5 − 𝑉𝑇4 + 𝑍𝑇4𝐼𝑇4 = 0
The solution to impedance estimation can be expressed as nonlinear equations


# Page. 6

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Result: impedance
• Real part has small errors as less than 1%.
• Imaginary part has relatively larger error rate than real part. This is because the
original value of imaginary part is smaller. With these acceptable error values,
our algorithm proofs the efficacy for voltage regulation.
ZT1
Technical specification
(Ω)
0.0436 + 0.0020i
Estimated Impedance
(Ω)
0.0436 + 0.0018i
ZT2
0.0436 + 0.0020i
0.0437 + 0.0024i
0.2
20.0
ZT3
0.0436 + 0.0020i
0.0433 + 0.0027i
0.7
35.0
ZT4
0.0436 + 0.0020i
0.0437 + 0.0026i
0.2
30.0
ZT5
0.0948 + 0.0287i
0.0953 + 0.0280i
0.5
2.4
ZJ12
0.0512 + 0.0267i
0.0508 + 0.0267i
0.8
0.0
ZJ23
0.0512 + 0.0267i
0.0511 + 0.0269i
0.2
0.7
ZJ34
0.0512 + 0.0267i
0.0514 + 0.0263i
0.4
1.5
ZJ45
0.0512 + 0.0267i
0.0509 + 0.0269i
0.6
0.7
Error(%)
Re Imag
0.0 10.0


# Page. 7

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Coordinated Voltage Regulation
Individual
Inverter
Capacity
Reactive
Power
Coordinated
The rest of
inverter
ΔPloss
Active
power
User1
User2
User3
User1
User2
User3
Voltage
Specific
Range
House #
House #
All users share the Reactive Power supplies to avoid
restricting Active Power
7


# Page. 8

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Result: Coordinated voltage regulation
• Objective function: Maximize σ𝑛𝑖=1 𝑃𝑖 (𝑛: 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 ℎ𝑜𝑢𝑠𝑒ℎ𝑜𝑙𝑑𝑠)
Generaton loss during the
simulation period (120 secs) [Wh]
• Constraint： voltage
capacity of inverter
Vlower_limit &lt; 𝑉𝑖 &lt; 𝑉𝑢𝑝𝑝𝑒𝑟_𝑙𝑖𝑚𝑖𝑡
2
𝑃𝑖2 + 𝑄𝑖2 &lt; 𝑆𝑚𝑎𝑥
120
CVR :
Coordinated voltage control
100
80
IVR :
Individual voltage control
60
40
T-node2, 3, 5 and 6 have PVs.
20
0
IVR CVR IVR CVR IVR CVR IVR CVR IVR CVR
T node 2
T node 3
T node 5
T node 6
total
Total active power loss is reduced by almost
80% in CVR.
8


