IEEE Power & Energy Magazine - November/December 2020 - 48

which requires various kinds of system flexibility, including balancing the active power in different time domains.
Power imbalances are traditionally caused by shortages of
supply capacity, demand fluctuation, and the disconnection of service. Under high penetration levels of variable
generation, however, the inconsistency and uncertainty
of variable generation, i.e., errors in generation forecasts
because of weather changes, are emerging causes of power
imbalances. These forecast errors are difficult to remove
completely, and extreme forecast errors have strong negative impacts on the operation of power systems that have
a high penetration of variable generation. On the other
hand, additional sources of flexibility are emerging and
expected. Examples include the flexible operation of traditional generation plants, such as thermal, hydropower, and
pumped-storage hydropower (PSH); the advanced management and control of distributed generation, such as PVs
and wind; and, in the future, manageable demand, such as
heat pump water heaters (HPWHs), electric vehicle (EV)
charging, and distributed storage.
This article discusses the difficulties encountered during, and the enhancement of, the power system operations
of the Kyushu Electric Power Company (EPCO), which has
increasing penetrations of PV and wind generation, by presenting the latest status of renewable energy deployment in
Japan in general and specifically on the island of Kyushu.
It details the challenges that have been faced and the countermeasures adopted in Kyushu at the transmission and
distribution levels. Additionally, it describes the challenges
and technical possibilities of a national renewable energy
deployment strategy and delivers our conclusions.

Renewable Energy Deployment in Japan
In 2012, the year following the East Japan Great Earthquake and the subsequent nuclear disaster, the government launched the FIT program to accelerate renewable
energy deployment. In 2014, the government revised the

national basic energy plan, which announced the mass
deployment of renewable energy as a national strategic
target. This plan and the 2015 long-term energy demand
and supply outlook both projected that the demand and
supply balance of energy and electricity in Japan in 2030
will include annual shares of renewable generation ranging from 22 to 24%. As shown in Table 1, which was
sourced from the Ministry of Economy, Trade, and Industry (METI), the current PV capacity is nearly 80% of the
expected total of 64 GW in 2030. In the meantime, several
committees have been working to establish a strategy for
a future energy system, including making improvements
and essential revisions to the FIT program and related
institutional rules. Considering that the applied capacities
in the FIT program, including those that have not been
deployed yet, are 82.3 GW for PVs and 10.8 GW for wind,
respectively, the proposed renewable generation share of
22-24% can be realized.
Many applications and implementations of PV generation, however, are concentrated in small balancing areas
where land prices are lower. As shown in Figure 1, PV
generation occupies the largest share of new installations
of renewable energy systems under the FIT program.
Such an uneven deployment of PV sources has created many
concerns about Japan's future energy and social systems.
Examples of those concerns include issues regarding the
increased FIT surcharge levied on consumers, the challenges
confronting power system operations as a result of one-sided
PV deployment, impacts on deregulated wholesale power
market operation, environmental ramifications for local
communities, and issues regarding the treatment of decommissioning waste from future PV systems.

The Current Situation in Kyushu

The power system in Kyushu, the southernmost of the four
main islands of Japan (as illustrated in Figure 2) has been the
most severely affected by the rapid and heavy PV generation penetration. In the Kyushu area, which
is interconnected with Honshu, the
table 1. The progress toward renewable energy capacity deployment
largest island, by the Kanmon interbefore and after FIT, as of March 2019.
connection line, the peak load is
Percentage
16 GW during the summer and the
After FIT (A)
Target (B)
of Target in
winter, and the minimum daytime
Before FIT
(as of March
(Fiscal Year
Operation
load is 8 GW. The supply capacities
(June 2012)
2019)
2030)
(A)/(B)
are 4.2 GW from four nuclear power
Geothermal
0.5 GW
0.6 GW
1.44-1.6 GW
37
plants and 2.3 GW from PSH.
Bioenergy
2.3 GW
4 GW
6-7.3 GW
60
Figure 3 graphs the recent PV
deployment in Kyushu. PV generaWind
2.6 GW
3.7 GW
10 GW
37
tion in Kyushu expanded by seven
Solar PV
5.6 GW
50.2 GW
64 GW
78
times in only six years after the
Hydro (medium
9.6 GW
9.7 GW
10.9-11.7 GW
86
launch of FIT in 2012. By the end
and small)
of March 2018, the PV capacity had
reached 8.53 GW, which is comThe targets accord to the 2015 long-term energy demand and supply outlook. (Source:
METI; used with permission.) When the target is a range rather than a specific value,
parable to the minimum daytime
the percentage of the target for the operation is based on the middle of the range.
load. Figure 4 compares the PV

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