［ Energy Management System ］

Our Approaches to the Wide-Area
Operation System for Distributed
Energy Resources like Wind
Power, Low Carbon Technologies
Development, and Verification
Projects
Keywords

Shin’ichi Sano,
Yohei Hasama,
Toshiharu Kurihara,
Takayuki Tanabe

Renewable energy, Energy storage system, System stabilization, High-speed WAN network, Generation plan

Abstract

For three years from Fiscal 2012 to 2014, we joined the “Experimental Studyon Wide-Area Operation System for Distributed Power Sources Like Wind
Turbines” carried out as part of the Low Carbon Technologies Development andveriﬁcation projects sponsored by the Ministry of the Environment. We havebeen working on technical developments to promote the wider introduction ofrenewable energy resources. In this “Veriﬁcation Project,” a system was createdto centrally monitor renewable energy resources distributed in a wide area
through high-speed WAN network and to stabilize the power network system byusing an energy storage system in a single location. At the same time, we worked
hard to resolve the practical problems through a veriﬁcation and evaluation
process. While there are some concerns about negative impacts of power quality and the instability of renewable energy on the utility grid, the above technologies are expected to contribute to the amount of increasing acceptance of theinterconnection of renewable energy resources to the utility grid.

1 Preface
Under the trade system of Feed-in Tariff (FIT)
that began in Fiscal 2012, the interconnection
capacity of Renewable Energy resources (REresources) mostly by photovoltaic power generation
has rapidly increased. Consequently, there is concern that power quality and power system instabilityof RE resources may adversely affect the utility grid.
In fall 2014, the power produced by a power utility at
authorized facilities exceeded the minimum demand
from the utility grids, and the request for interconnection with utility grids was suspended temporarily.
In this way, challenges with supply and demandbegan to surface. These adverse inﬂuences of RE
resources to utility grids are caused by short-term
output ﬂuctuations, unreliability in generation output, or concern regarding the generation of surplus
power. If the generation output of the RE resources
is predicted in advance and short-term output ﬂuctuations can be suppressed in combination withenergy storage systems, system management conforming to the generation plan may be realized and
it is expected that most of the aforementioned problems may be eliminated. In a system where storage
batteries are installed in each power station tosecure system stability, however, there is a limit offorecast accuracy for generation output that is thebasis for the planned system management. This will
create a problem such as the capacity of necessarystorage batteries may become too excessive.
To solve this problem, the “Experimental Studyon Wide-Area Operation System for Distributed
Power Sources Like Wind Turbines” (the “Veriﬁcation
Project”) was carried out for three years during
Fiscal 2012-2014 as a demonstrative research project sponsored by the Ministry of the Environment
in Japan. This project is intended to smooth thegeneration output through virtual integration of
widely distributed RE resources. In addition, further
improvement of accuracy is attempted by cancelingmutual forecast errors among generation sites so
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that the total capacity of storage batteries in kW
considered necessary for the system as a whole canattain 50% of the total capacity of RE resources.
Fig. 1 shows an overall image of this Veriﬁcation
Project and Fig. 2 shows its concept.
For this Veriﬁcation Project, we oversaw the

3 wind turbines
in Wakkanai City
(1.98MW)wide-area operation system building including thecontrol of storage battery system. We conducted
technical development to realize real-time control
through high-speed WAN network. This paper introduces the contents of the wide-area operation system and the results of the technical development.

Wakkanai photovoltaic (1.0MW)

Wakkanai megasolar power station
Sodium sulfur: 500kW/7.2h
LiB:100kW/2h
EDLC: 100kW/1min

Wide-area operation
systemTown of Tomamae windturbines 3 units (2.2MW)② Development of high-precisiontime synchronization method③ Development of high-speed
data transmission system

Town of Shihoro
biogas power
generation system(25kW)

Control
approach④ Development ofcontrol approach

Japan Weather Association(Generation forecast system)

Town of Setana windturbines 2 units (1.2MW)

Fig. 1

Date City
photovoltaic(1.0MW)

Weather forecast system① Development ofgeneration forecast
system

A Whole Image of the Verification Project

Renewable energy power that has been distributed to various places in the Hokkaido
and intensive monitoring in the wide-area information communication network, tostabilize in one place of the power storage system.

Large output
fluctuation

Conventional
Confirm the effectof battery capacity
reduction by reviewing the operation concept.
→Toward expansionof renewable energy introduction

Countermeasures by
each generation site

Characteristics
singular tothe site
Generation
forecast

Limits inforecast
accuracy
improvement

SmoothingeffectHigh-speed kW
communic- reduction
ation

Establishment ofcontrol and operation technology
Reduction ofnecessary battery
capacity

Synchronized kWh reduction kWh reduction
measurement

Establishment ofwide-area forecasting technology

Improvementof forecasting
accuracy
Active use of controllable energy

Fig. 2Concept of the Verification Project

The conventional operation concept was signiﬁcantly reviewed and the capacity ofthe batteries in kW needed for the entire system was reduced to increase the volume of introduced renewable energy.

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MEIDEN REVIEW Series No.169 2017 No.1

2.1 System Conﬁguration
For this Veriﬁcation Project, three
existing wind farms and two solar
farms installed in Hokkaido were chosen as the measuring targets, all systems of which we built. Fig. 3 shows animage of system conﬁguration. With
help from Wakkanai City Government,
our output constant control equipment
was installed on the premises of the
Wakkanai Megasolar Power Station(Wakkanai MS) constructed under thetitle of the “Veriﬁcation of Grid Stabilization with large-scale PV Power Generation Systems” sponsored by the
New Energy and Industrial Technology
Development Organization (NEDO), a
national corporation for research anddevelopment.

2.2 Energy Storage System

Excessive
battery
capacityThis project

2 Wide-Area Operation
System Building

In the energy storage system, three
types of energy storage devices withmutually different characteristics wereadopted to verify the effect of improvement of control performance throughcoordinated control and examined theeffect of reducing the battery capacity.
For sodium sulfur batteries, existing facilities installed at the Wakkanai MS
were utilized. Lithium-ion Batteries (LiB)and Electric Double Layer Capacitors(EDLC) were newly installed. With ahope of further reducing the battery
capacity, a biogas power generation
system was installed in Town of Shihoro
as a controllable RE resource. For thebiogas power generation system, a gas
container was used as a means for energy storage. In this manner, althoughsomewhat inferior in terms of fast-Wakkanai(Existing)Long-term output fluctuation

System operation
flow

Weather forecast system

Weather
forecast

Weatherobservationequipment

Tomamae(Existing)

Weather andgeneration
forecasting
equipmentⒶGeneration
forecast
Generation output
forecast at theintervals of 30min

30min

Setana(Existing)

Output-constantcontrol equipment
Wakkanai(Existing)ⒷGeneration
outputDate(Existing)Renewableenergy generation sitePowermeasurement

EDLC
(New)

Communication
network
High-speed
data transmission

Control

Sodium LiB
sulfur(New)(Existing)

Smart
meter

(a) Sodium sulfur battery

Battery system

Controlterminal

Biogaspower(New)ⒸFluctuations to be absorbed(Ⓑ－Ⓐ)
Wide-area operation system

Fig. 3

Image of System Configuration

The RE generation output is obtained from each site throughsmart meters and, a wide-area communication network, and adifferential component (ﬂuctuation) from the computed generation goal value is compensated by using batteries and biogas
power based on the result of the weather forecast.

Table 1 Capacities of Storage Batteries and Biogas PowerIn ﬂuctuation components, short-term output ﬂuctuation of EDLC,
middle-term output ﬂuctuation of LiB, and long-term output ﬂuctuation of sodium sulfur batteries are respectively regarded ascompensation targets. The biogas power is designed to playa role of maintaining 50% state of charge in sodium sulfur
batteries.
Classification

Capacity (kW )Battery capacity

Sodium sulfur batteries

500

7.2h

LiB

100

2h

EDLC

100

1min

Biogas power

25−

response speed, it can be used as a source of capable regulation like that of storage batteries. Table 1
shows the capacities of storage batteries and biogas power generation system. Fig. 4 shows an external appearance of the energy storage system.

2.3 High-Speed WAN Network
In a high-speed WAN network, it is necessary
to integrate the generation outputs of widely distributed RE resources through a wide-area communication network. Accordingly, data transmission delay
and instability in transmission cycles in communication networks are the subject of some issues. For(b) LiB・EDLC

Fig. 4

Energy Storage System

In regard to sodium sulfur batteries for this veriﬁcation project,
500kW was borrowed from existing batteries with a total capacity of 1500kW (switched over in accordance with the right of control). LiB and EDLC were individually accommodated in the dedicated containers.

this reason, we decided to adopt a virtual dedicatedline with a secured bandwidth for the wide-areacommunication network. Since many RE resources
are distant from urban areas, optical lines without
any concern in performance are not always available. We therefore selected three types of lines
such as optical lines, ADSL lines, and ISDN lines,
for our evaluation. Since telemetry data for the RE
resources at each power generation site call fortime synchronization, a time synchronization method conforming to IEEE1588 was adopted because
this method has recently been getting increased
attention. Thus, a high-accuracy timestamp could
be assigned. Due to adopting this method, a timesynchronization accuracy within ±50ms in conjunction with the master clock device was realized only
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Operation management
systemBatteries andcontrol terminals

Table 2
Optical lines

High-speed
wide-area network(dedicated lines)

Internet(ordinary lines)

Fig. 5

Mobile lines
Biogas power

Image of High-Speed WAN Network

For high-speed data transmission, each site was connected
through dedicated optical lines. In consideration of possible various issues during the commercialization process, ordinary lines(optical and mobile) were also applied through ADSL, ISDN, andInternet.

through network communications. Realizing thisgoal accuracy is signiﬁcant because it is essential toevaluate the experimental test results and it is alsoa means to prove system control performance.
Meanwhile, considering the commercialization
steps, its expected use of dedicated lines demandmight be a cost burden. For this reason, control
response characteristics by using ordinary lines
were also veriﬁed and evaluated. In this case, twotypes of lines, both optical and mobile, were adopted. Fig. 5 shows an image of a high-speed WAN
network.

2.4 Wind Turbine Operation State Monitoring
System
In this Veriﬁcation Project, the measuring subject window power generation systems are small
scale and three wind turbines are installed. In addition, there is no installation of a Supervisory Control
And Data Acquisition (SCADA) system for the control of this wind farm. It is, therefore, difﬁcult to grasp
the state of operation accurately. Meanwhile, weather forecasting equipment is used to estimate thewind velocity based on weather forecast data thefollowing day, and estimates the next-day generation output based on the past generation record. For
this reason, it is essential to grasp the state of operation of RE resources correctly. At the stage of
operation and in the case of wind turbine stoppageis due to system malfunction, it is necessary to makeadequate adjustment of power yield forecast data
per the availability state. Against such background,16

The surveillance camera requires maintenance such as periodic
removal of contaminants from the lens. Since the precisionsound level meter and Charge Coupled Device (CCD) camera
can have obstructive factors like weather, it is necessary to
use technologies to eliminate various disturbances (examples:noise-producing moving objects, birds, airplanes, etc.).
Monitoring
approachWind power
generation site

Photovoltaic
generation site

Wind Turbine Operation State Monitoring
Approach and Result of Evaluation

MEIDEN REVIEW Series No.169 2017 No.1

Detection
objectJudgment
methodSurveillancecameraImage of whole Visual
wind turbine

Precision
sound level
meter

Wind noise

CCD camera Blade image
Vibration
sensor

Evaluation
Obstructive factor:
Weather, etc.

Frequency Obstructive factor:
analysis
Individual difference
Image
Obstructive factor:
differential Slight movement

Tower vibration Frequency No obstructive
acceleration
analysisfactor (Adopted)

we examined the monitor system building to grasp
the state of the wind turbine operation. Table 2
shows our state of wind turbine operation monitoring approach and the result of the evaluation.
According to the result of our preliminary investigation, we constructed a wind turbine operation
state monitoring system assuming in which “vibration acceleration” is a detection target with which
the state of wind turbine operation can be identiﬁed
most effectively. Each wind turbine is generally
installed at a separation distance of a few hundred
meters. As a result, at the existing power station, it
is difﬁcult to secure a wired communication route
between wind turbines. We then decided to install amulti-hop type monitoring network that employs asmall-power wireless device. Such a system does
not require any large-scale modiﬁcation in existing
facilities. Fig. 6 shows the wind turbine operation
state monitoring system and an installation image.

3 Evaluation of Wide-Area Operation
System
3.1 Control Response Characteristics
Table 3 shows the result of performance evaluation for the high-speed WAN network used in awide-area operation system that has been installed
for this Veriﬁcation Project. It was conﬁrmed thathigh-speed and steady communication performance can be attained irrespective of the line typeused, if dedicated lines are employed. If ordinarylines are used, however, it was veriﬁed that a sufﬁcient level of communication performance can beattained in the case of optical lines, but mobile lines

External appearance

Contents

Wind turbine operation detecting device

Transmission delay (ms)9-axis vibration
sensor

150
Max.

Average

100
50
Min.
0

00
：0
0：
02 00
：0
0：
04 00
：0
0：
06 00
：0
0：
08 00
：0
0：
10： 0000：
12： 0000：
14： 0000：
16： 0000：
18： 00
00
：
20 00
：0
0：
22 00
：0
0：
00

Wind turbine
interior(a) Wind turbine interior

Time

Japan Sea

Fig. 7

Wood fenceWind turbine
No.1

InsideElectricity room

InsideWind turbine
No.2

Wind turbine
No.3

Smart
meter

Radio
deviceBattery

Operation
management
system(Wakkanai MS)

Radio device accommodating BOX(b) Overall configuration

Fig. 6Wind Turbine Operation State Monitoring System
and Installation Image

An integrated unit of a vibration sensor and radio was installedon the inner wall of wind turbine tower No.1〜No.3. Each unit wasused to transmit detected information to a radio master devicefor data collection via the closest radio relay device (outdoor).

Table 3Result of Performance Evaluation for HighSpeed WAN Network

Target performance was realized with all types of lines except an
ordinary mobile line.
Circuitclassification

Time synchronization(ms)

Dedicated Optical
line
ADSL

±0.3

10

Target attained

±0.7

16

Target attained

ISDN

±8

38

Target attained

Optical±725

Target attained

Mobile±17

102

Conditional

Ordinaryline

Transmis- Performancesion delay
evaluation(ms)

caused a large communication delay. As shown in
Fig. 7 and Fig. 8, it was also conﬁrmed that thecommunication speed of an ordinary line tends tocause unstable changes. Since the transmission
quality and communication cost of the dedicatedand ordinary lines have a relationship of trade off, it
is necessary to choose an adequate communication line according to the control performance to be
secured in operation.

Transmission delay (ms)InsideAlthough the transmission speed tends to change greatly in atime frame from evening to next morning, we conﬁrmed that optical lines can be used in almost same way as dedicated lines.

1000
800
600

Max.

Average

Min.

400
200
0

00
：0
0：
02 00
：0
0：
04 00
：0
0：
06 00
：0
0：
08 00
：0
0：
10： 0000：
12： 0000：
14： 0000：
16： 0000：
18： 00
00
：
20 00
：0
0：
22 00
：0
0：
00

InsideInstability in Ordinary Optical LinesTime

Fig. 8Instability in Ordinary Mobile Lines

Like optical lines, the transmission speed tends to change greatly in a time frame from evening to the next morning. Target performance cannot be attained. Mobile lines are, therefore, applicable to areas where high-speed control is not required andwhere biogas power or wired lines are not available.

3.2 Wind Turbine Operation State Monitoring
SystemFor the wind turbine operation state monitoring
system, we conﬁrmed its operating conditions bygathering necessary data for one month. Fig. 9shows the result of judgment on wind turbine power
yield, wind velocity, and running. In the time zone
where power generation is 0kW, a judgment of
non-operation (OFF) is correctly indicated. In regard
to a part marked by an arrow in the ﬁgure, however,it was identiﬁed as a record caused by false detection. As a result of our analysis on the test data, weconcluded that judgment accuracy can be improved
further by reviewing the detection threshold value
and improving the judging method.

3.3 Result of Long-Term Continuous Operation Test
For this Veriﬁcation Project, we carried out along-term continuous operation test for about two
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Generation capacity (kW)

9

160

8

140

Wind velocity

120

Result of operation judgment

7

Generation capacity

6

100

5

80

4

60

3

40

2

20

1

0
2015/1/24
18：00

2015/1/24
22：48

2015/1/25
3：36

2015/1/25
8：24

Error detection

Fig. 9

10

Result of judgment on generation capacity, wind velocity,and operation of Tomamae WF Wind Turbine No.1

18002015/1/25
18：00

2015/1/25
13：12

Error detection

Wind velocity (m/s)・
Operation judgment (1＝ON 0＝OFF)

200

Error detection

Result of Judgment on Wind Turbine Generation Capacity, Wind Velocity, and Operation

When the wind turbine was in operation, vibration acceleration was dispersed (standard deviation became large). When it was out ofservice, the distribution of vibration acceleration was settled in a constant range with the standard value in the center. 9-axes of operation
judgment was put into effect by vibration acceleration of the X, the Y and the Z axis detected by vibration sensor.

100
90

Max: 88%

80

SOC (%)

70

Max: 70%

60
50
40
30

With reflection

Without reflection(Data valid after
19 December 2014)

41% reduction

Min: 23%

20
10
0

20
14
/1
1/
20
1
14 4
/1
1/
20
1
14 9
/1
1/
20
2
14 4
/1
1
/2
20
9
14
/1
20 2/04
14
/1
2/
20
09
14
/1
20 2/1414/1
20 2/1914/1
20 2/24
14
/1
2/
20
28
15
/0
1/
20
02
15
/0
1/
20
0
15 7
/0
1/
20
1
15 2
/0
1/
17

Min: 0%Year, month, day

Fig. 10

Effect of SOC Variation Range Reduction for Sodium Sulfur Batteries with or without Reflection by Wind Turbine
Operation

The SOC of batteries is considered ideal if it maintains around 50% consistently so that the batteries can respond in both cases of charge
and discharge. In this testing, not only the result of weather forecast was used but also the wind turbine operation state was added inorder to calculate the generation target value. In this manner, we could greatly reduce the SOC variation range of sodium sulfur
batteries.

months since November 2014. Through this testing,
we conﬁrmed that the wide-area operation system
built this time can deliver stable operation. During
the test, we also carried out operation reﬂecting theconditions of the wind turbine operation, and madea comparison of control performance with a casewhen the state of wind turbine operation was notconsidered. As shown in Fig. 10, the result of theevaluation indicates that the State Of Charge (SOC)in the sodium sulfur battery can greatly reduce its
variation range by reﬂecting the conditions of thewind turbine operation. This fact signiﬁes that the18

MEIDEN REVIEW Series No.169 2017 No.1

required capacity of storage batteries can be
reduced substantially.

4 Postscript
In this Veriﬁcation Project, we could realize theoriginal target performance for the wide-area operation system and conﬁrmed that programmed operation of RE resources is possible in an effective andstable manner. By collecting the basic data about
performance evaluation of the communication network and status monitoring of the conditions of wind

turbine operation, we identiﬁed issues for futurecommercialization with a wider introduction of RE
resources. We expect that our technologies will be
actively used to increase the interconnection capacity of utility grids with RE resources.
Lastly, for the implementation of this Veriﬁcation
Project, we express our deepest gratitude to Wakkanai
City Government and project-related organizations,such as Japan Weather Association (the chief representative of undertaker for contract research forthis veriﬁcation project), and joint implementation
organizations: Hokkai Electrical Construction Co.,

Inc., HOKUDEN SOGO SEKKEI Corporation, andHokkaido University. We appreciate your generous
cooperation such as installation of test equipment at
the existing RE resource power station and the acquisition of power generation data. Our special
thanks to Hokkaido Telecommunication Network
Co., Inc. for your cooperation in building the unprecedented high-speed WAN network.
・All product and company names mentioned in this paper are
the trademarks and/or service marks of their respective owners.

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