Project Subjects
Integrated Operation and Control Techniques of Supply andDemand Sides in Autonomous Demand Area Power System
Background and Objective
Penetration of distributed power generation (DG) using renewable energy may be accelerated to copewith the problem of global warming. Photovoltaic power generation (PV) is expected to be a main renewableenergy source in Japan. In addition to establishing the techniques in a utility distribution system level for gridstability, developing integrated operation techniques for both supply and demand sides including utilization ofDG will be required for large penetration of DG. The purpose of the study is to develop proper operation andcontrol techniques of Autonomous Demand Area Power System (ADAPS) using integrated technique of supply
and demand sides to facilitate smooth introduction and efﬁcient use of DG with renewable energy sources.

Main results
1. Development of utilization technique of PV surplus power
As a measure for coping with the surplus power problem with large penetration of PV, a planning method
on next day operation of customer loads was proposed (Fig. 1-a). A heat pump type water heater, which has ﬂexibility in its operation, was selected for the target of the control. The effectiveness of the method was conﬁrmed
through simulation in which annual supply and demand of a customer is analyzed using relationship between
weather forecast and actual PV power output, load consumption data, etc. In the simulation, required limit ofreverse power to the grid was changed as a parameter. The results show that PV energy loss due to reverse power
limit*1 can be reduced remarkably by the method so that the maximum monthly loss reduction rate reaches about
60% (Fig. 1-b) [R09023].
2. Stable operation of PV in voltage sag
To keep grid stability with large penetration of PV, it is required that each PV, for instance, recovers its
generation power immediately after a voltage sag caused by a lightning strike on a transmission line. A voltage
sag test of Japanese representative 10 power conditioners (PCS) for PV by 9 manufacturers was carried out. The
results show that improvement of PCS control method is needed because output power of PCS generally tends tochange remarkably after a voltage sag (Fig.2) [R09015].
3. Voltage regulation method of ADAPS taking account of customerʼs power factor
In examining voltage management of a distribution line in the near future, a voltage rise due to the “Ferranti effect” due to static capacitor installed in high voltage customers for power factor improvement should betaken into account in addition to the voltage rise due to reverse power ﬂow from PV. A simulation study wasconducted to establish proper voltage control methods with distribution line control devices such as SVC andSVR. The results show that combination of SVC with a centralized control*2 and SVR is highly promising inminimizing both device capacity and distribution line loss (Table 1) [R09014].

*1: Restrained PV generation energy for satisfying required limitation of reverse power.
*2: SVC control with remote communication functions to keep distribution line voltage within proper range for whole
distribution line.

68Environmental and Energy Utilization Technology<ADAPS>

Storagebattery

Estimation ofEstimated
total
whole
surplussurpluspower
power
fromfrom COS
uppersystem

Distribution line
Restraining
reverse power

Substation
Centraloperation
COCSsystemPV system

Operationplanning ofADAPS・Decision ofreverse power
limit of eachcustomer

Power energy loss（kWh/day）

Uppersystem

8kW

Control devise

Operationplanningof customer’s
appliances

Information
ControlTime

Storage batteryor PHEV,EV(SDI)

Large

6

No measure

54

Upper limit of reverse
power: 2kW

32Air
conditioner

Upper limit of reverse
power: 1kW

Proposed

No measure

1HP typewater heater

Small

Solar radiation

7

Proposed

0Others
Others

4567<Customer>

89month101112(b) Example of improvement of customer average daily PV energy loss in every month
4kW PV is assumed. If necessary, HP type water
heater is operated during daytime for PV energy loss
reduction. Upper limit of reverse power from customer
to the grid is set constant during a year for the sake ofsimpliﬁcation.

(a) Concept of operation planning method of customerʼs loads for coping with surplus power
The method carried out only when surplus power for the wholegrid is expected according to weather forecast, etc. Uncertaintyof forecast is taken into account in the method using past statistical data.

Fig. 1 Concept and effect of proposed customer operation planning
method of next day for utilization of PV surplus power
Term瞬低期間of voltage sag

Outputcurrent
出力電流
4040

流 （A)
(Ａ)
電 電(A)
流

30

2020
1000-10-20-20-30-40-40- 0 .2- 0. 1
-0.1

0 .0
0.0

0 .1
0.1

0 .2
0.2

0 .3
0.3

時 間 （秒 ）

0 .4
0.4

0.5
0.5

0 .6
0.6

0 .7
0 .8
0.7
0.8(sec.)(秒)

Output
power
出力電力
5.0

電 (kW,
力 (kW/kVar)
kVar)

5.00 0Effective
有効電力

4.0

電力（KW・KVar)

4.00 0

瞬低回復後
Variationに出力変動
occursaftervoltage^sag.
が発生

3.0

3.00 02.0

2.00 0

Reactive
無効電力

1.0

1.00 00.0

0.00 0-1.0- 1.00 0- 0 .2-0.1- 0 .1

0.0

0 .0

0.1

0 .1

0.2

0.3

0.2

P0 .3
時 間 （秒 ）
Q

0.4
0 .4

0.5
0.5

0.6
0 .6

0.7
0.8
0 .7
0.8(sec.)(秒)

Fig. 2 Example of operation characteristics of PCS for PV in the event of voltage sag
The result is in case that voltage reduction rate is 30% and voltage sag continuance time is 0.5 sec. It is clear that PCS
output power changes remarkably just after voltage recovery.
Table 1

Controlled
devicesComparison of voltage regulation methods using SVC and SVR
Conditions
Installed site
Controlin distribution
methodline

Loss indistributionline（kWh）

Results
Required
capacity(kVA)

Evaluation

SVC

Local

Middle, End1036

1757

△SVC

Centralized

End8731740△SVC+SVR

Centralized

End6841044○Note; Range of PV penetration ratio to maximum demand of distribution line is 0 to 100%. Necessary
device capacity by which voltage can be controlled below 106V is calculated.

69