DEMONSTRATIVE PROJECT ON
GRID-INTERCONNECTION OF CLUSTEREDPHOTOVOLTAIC POWER GENERATION SYSTEMSNew Energy and Industrial Technology
Development Organization(NEDO)

Demonstrative Test Site

Ota, Gunma-preOsaka
TokyoLocation of Ota city

Test site in Ota city2

Objective
Clustered grid connected PV systems in local area possibly induce unprofitablephenomena to power system.
Such as•Voltage swell by output of PV systems (should be 101±6V, 202±20V)•Unintentional Islanding (Not allowed)•Harmonics (should be less than 5% on high voltage distribution line ) etc.,

The objective of this program is to demonstrate as follows ;1.Development of the technology to avoid restriction of PV system output
2.Analysis and Development of function to prevent unintentional islanding
3.Analysis and evaluation of harmonics
4.Development of applied simulation technologies
Period of this program： FY2002 to FY2007
3

Development of technology to avoid
restriction of PV system output （SUBJECT 1)
The voltages in distribution line sometimes becomes
higher than the maximum nominal voltage of 107V or 222V
because too much power injection from PV system. In suchcase, output of PV is restricted to keep line voltage within
operational range (101±6V, 202±20V).
Various suppressions of the PV output are analyzed, andthen new technologies to reduce such suppressions aredeveloped in this project.
Voltage

Near end of feeder

Operational range
Substation point

Distance

Power injection from PVPVPVPVPVPVPV

4

System Configuration
High voltage
distribution line

PV arrayPV
Low voltage
distribution line

Connection box
Relay box)

Residential complex
Residential loadOutdoor battery box(PCS, storage battery)5An example of proposed solution to avoid
restriction of PV system output
Utility grid① time to flow output② time to flow inPV array

PCS
household appliances／ grid～①① time to charge- when voltage swell at
AC output side of PCS ishappened.
- when PV output is larger
than demand.

②② time to discharge- demand period

Battery

Scheme of a residential PV system
6

Analysis and Development of function to prevent
unintentional islanding(SUBJECT 2)
・ A function to prevent islanding operation disconnects thePV system from the power grid in the case of service
interruptions. Interferences among the equipments forpreventing islanding are induced when the clustered PV
systems are installed.
・ Methods to avoid mis-actuations of such function in theclustered PV systems are developed, the methods will beverified through demonstration.

7

Analysis and evaluation of harmonics(SUBJECT 3)
Clustered PV systems tend to increase the higher
harmonics because of increase of inverter. Such harmonics
negatively influence to equipments in the power systems
and household appliances.
In this project, analysis and evaluations are made using
data correlating the number of PV systems and themeasured harmonics induced from them.

8Development of applied simulation technologies(SUBJECT 4)
Simulation methods covering a wide use are developed
based on the data and the results obtained in the above 3subjects.
The simulations are designed to contribute to planning ofother clustered grid-connected PV systems and precise
evaluation of the data obtained in this project.

9

Test Facility
Integrated power conditioner（4kVA）

Number of PV：553
Total Capacity：2,129kW
Average of installed PV capacity : 3.85kW
Ratio for the whole PV (%)

Fan3530252015105Components of outdoor battery box＜ＰＰ
≦

≦

4.5

4.5

4.0＜≦Ｐ
4.0

Control terminal

3.5

Lead-acid battery(4,704Ah・cell）

3.0≦

Ｐ＜Ｐ＜3.5

3.00

PV Array Range of Rating (kW)Capacity of PV system(as of Aug. 2006)

10Schedule of Activities
FY

2002

2003

2004

2005

2006

2007

Field test

Comprehensive
evaluation

Development oftechnology to avoid
restriction of PV output

Developmentof prototype

Development offunction to prevent
unintentional islanding

Comprehensive
Field test andevaluation
Study of test method simulation

Analysis and
Evaluation of Higher
HarmonicsStudy oftest method Field test and simulation

Development ofapplied simulation
Number of installed PV
system( accumulated )Comprehensive
evaluation

Development of applied simulation
0(0)130(130)

198(328)

167(495)

58(553)0(553)
11