Principal Research Results

Development of Operation and Control Method for Autonomous
Demand Area Power System− Study on Method for Regulating Voltage according toInterconnection Rate of Dispersed Generation−
BackgroundIn recent years, there is growing concern over impact on the operation and control of power distribution systems caused byexpanded connection of distributed generation. To cope with such problems, Autonomous Demand Area Power System (ADAPS)＊ 1
was proposed as a new power system and the methods of operation and control ＊ 2 for voltage regulation and loss reduction weredeveloped using Loop Power Flow Controller. The effect of voltage regulation and loss reduction became clear by computer simulation and demonstration tests. To develop ADAPS, it is necessary that suitable voltage regulation method is evaluated by computer
simulation in some interconnection areas and different forms of DG.

Objectives
Voltage regulation methods are evaluated from the viewpoint of regulation effect, cost and distribution loss, and suitable
method according to interconnection rate becomes clear by computer simulation for voltage regulation in some areas, distribution,
power factor ＊ 3 and interconnection rate ＊ 4 of DGs.

Principal Results
1. Study on voltage regulation method according to interconnection rate
In model area shown in Fig.1, the effect of the main voltage regulation method ＊ 5 was analyzed by computer simulation,and suitable voltage regulation method becomes clear according to the interconnection rate (Fig.2).
(1) When DGs are distributed equally in residential areas, without controlling reactive power of DG output, voltage control is necessary in the case where the interconnection rate is 32% or more. With controlling reactive power of DG output, centralized voltage
control is necessary in the case where the interconnection rate is about 60% or more.
(2) When DGs are concentrated on the end of feeder in residential area and commercial areas, voltage regulation control by DG or
SVC control by self-end information is effective.
2. Evaluation of voltage regulation method in the viewpoint of cost and distribution loss
The conditions to apply SVC and LPC control that is shown above become clear from the viewpoint of cost and distribution loss.
(1) From the viewpoint of cost, price per kVA of LPC is effective regardless of the interconnection rate. In the case of voltage regulation control at one side of a loop point, the price per kVA of LPC is 1.2 or less times of the price per kVA of SVC. In the case ofvoltage regulation control at both side of a loop point, the price per kVA of LPC is 2.1 or less times of the price per kVA of SVC.
(2) In the viewpoint of distribution loss, distribution loss of LPC is lower than distribution loss of SVC, and the difference (increase)according to interconnection rate is no more than 1%.

Future Developments
In the case where the interconnection rate of DG increases, problems of power distribution system will be extracted andmeasure method is studied.
Main Researcher: Satoshi Uemura, M.eng
Senior Research Scientist, Customer Systems Sector, System Engineering Research Laboratory
Reference
S. Uemura, 2008, “Development of Operation and Control Method for Autonomous Demand Area Power System: Study on Method
for Regulating Voltage according to Interconnection Rate of Dispersed Generation”, CRIEPI Report R07018 (in Japanese)＊1：Basic composition of the system is loop formation, and Loop Power Flow Controllers are set at the loop point, which control power flow andsystem voltage actively, and the system control voltage fluctuation and equalize power flow.
＊ 2：The operation and control is controlling LPC and transformer tap of substation to reduce distribution loss, to equalize power flow andregulate system voltage.
＊ 3：The value is minimum power factor that PV inverter can control to regulate system voltage.
＊ 4：The value is the rate of DG capacity to feeder capacity.
＊ 5：The control methods are to control DG reactive power, to control SVC by using connection point information, to control SVC by using information of whole distribution system, to LPC by using information of whole distribution system72

4. Power Delivery

Average value
is used asvoltage rise at
Low voltage
distributionsystem

Feeder
LPC- B

Looppoint

Both sideof loop point

Feeder is inte rconnect ed DG
LPC- C

Substation
for distribution
systemCommercial Area※

Commercial Feeder
3.5MVA

Feeder Length

3.65km1.93kmKind of DG

Photovoltaic

Co- generation※

Substation
Timeat Noonat 7 amfor distribution※Standard Model Feeder is published by Electric Technology Research Vol.37 No.3
systemOne sideof looppoint

Looppoint

Residential Area
Residential Feed er
3.5MVAFeeder Capacity

Feeder

LPC-AModeFeeder ModelFeeder

Fig.1 Model Distribution System for Commercial and Residential Areas

Kind of DG DG Distribution Power Factor of DG
Commercial
AreaCo-gene

Equally

７３Control is unnecessary

0.9(constant)

1〜0.85

１８1〜0.95

１８Voltage Regulation Control of DG (VRC)

End of FeederResidential
Area

３１

VRC and SVC control using Connection Point Information

PV
1〜0.85３２５７

1〜0.95

３２ ３５５８Equally

Interconnection Rate 0%

20%

40%

６６

VRC＋SVC control using Informationof Whole Distribution System or
VRC＋LPC control using Informationof Whole Distribution System

60%

80%

100%

Fig.2 Method for Regulating Voltage according to Interconnection Rate of Dispersed Generationin each Area

Power Factor 0.85
Power Factor 0.95

1.2
1.1
10.9

2.1

Power Factor 0.85
Power Factor 0.95

21.9
1.8

Distribution Loss [％ ]1.35Rate of Price per kVA in case
2.2 that LPC is effective

Price per kVA of LPC／SVC

Price per kVA of LPC／SVC

1.44

SVC Control using
Information ofWhole Distribution
System321LPC

01.7

00.8

Loss of LPC
control is lowerthan SVC

1.66080100Interconnection Rate of DG[%]

6080100
Interconnection Rate of DG[%](a) One Side of Loop Point(b) Both Side of Loop Point

20406080100
Interconnection Rate of DG[％]

Fig.4 Distribution Line Loss
(Residential Area, Concentrated on the end ofFeeder, Power Flow Loss of LPC is 5%)

Fig.3 Evaluation from the viewpoint of cost
(Residential Area, Distributed Equally）※Cost is (Required Capacity)×(Price per kVA)

73

Distribution Loss [%] ＝Distribution Loss [ kW]
Feeder Capacity [kVA]4