New Energy Horizons
Opportunities and Challenges
Northeast Asia Power System Interconnection and
Distributed Resources Operation Plans in South
Korea
Sang Seung Lee and Byung Ha Lee
S. S. Lee is with the KESRI, Bldg. 130, Seoul National University,
Seoul, 151-742, Korea (e-mail: ssLee6@snu.ac.kr).
B. H. Lee is with the Incheon National Univ., Incheon, Korea
IEEE PES General Meeting 2015, July 26 - 30, 2015
Sheraton Denver Downtown in Denver, CO., USA
INTRODUCTION
No. 2
New Energy Horizons
Opportunities and Challenges
This paper presents the Northeast Asia power system interconnection (NEA-PSI), distributed
energy resources (DERs) and energy storage system (ESS)-based operation strategies
targeting supply-demand balance (SDB) and stable operations for the South Korean power
system.
In the NEA interconnection and renewable energy sources (RESs) insertion, the Korean power
system should prepare large reserve capacities for unexpected transmission line disconnection
or connection.
To meet this requirement, the future energy management system (EMS) should be flexible to
include PSI, DERs, and ESSs in the unit dispatch to increase security in utilizing power system
interconnection, renewable energy, storage systems, and controllable loads to meet future
demands.
In this paper, we suggest how to design supply-demand balance strategies for stable
operations under unexpected situations for the NEA-PSI, DERs, and large-scale ESS insertion in
the South Korean power system.
IEEE PES General Meeting 2015, July 26 - 30, 2015
Sheraton Denver Downtown in Denver, CO., USA
I. Introduction
No. 3
New Energy Horizons
Opportunities and Challenges
Recently, various distributed energy resources (DERs) have been introduced into power
systems. These distributed resources, such as wind energy, solar cells, gas turbines, fuel cells,
etc., are being used for small-scale units; while combined-cycle units, hydrogen energy, and
small-size nuclear reactors, etc., are being used for medium-scale units.
Currently, the power supply of areas such as islands must increase the ratio of renewable
generation systems (solar energy, sea wind power, small water power, wave power, and small
nuclear reactors) to diesel generation systems [1]-[5].
Furthermore, some problems have remained, such as the power system interconnection and
the energy inter-cooperation between NEA countries. Solving the environmental problems
and the supply/demand problem in the South Korean power system is essential.
This may cause energy trade to increase greatly between NEA countries, of Russia, Mongolia,
China, North Korea, South Korea, and Japan. Because of these energy exchanges, both
environmental problems and the supply/demand unbalance of energy may increase in NEA
countries
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Sheraton Denver Downtown in Denver, CO., USA
I. Introduction
No. 4
New Energy Horizons
Opportunities and Challenges
After the NEA power system interconnection and DERs insertion, large stored capacities of
the interconnected power system are needed to prepare for unexpected disconnection or
connection of transmission lines and generation resources.
To solve this imbalance, ESSs have been developed worldwide to supply power systems with
stored energy. Frequency-regulated ESSs are a new technology that utilizes instant charge
and discharge, instead of regulating outputs of generation facilities to maintain the
frequency of a power system varying in real-time.
ESSs have the role of frequency regulation, by relieving the electrical power fluctuation or
oscillation to improve the power quality [6]-[19].
In addition, large reserve capacities of the ESS must be obtained, in preparation for
unexpected system imbalance, by increasing the number of generators in power plants, or by
decreasing the electrical load in the power system.
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Sheraton Denver Downtown in Denver, CO., USA
I. Introduction
No. 5
New Energy Horizons
Opportunities and Challenges
Among these regions, the areas that have difficulty in constructing new power plants must
be given special consideration, in terms of the life-time of the installed generators, and the
number of generators.
Efforts for storing surplus power during the night are continually ongoing; but currently,
these efforts have not involved using a large-scale power storage method, except for
pumped storage generation.
Since they are mostly situated in remote regions, a pumped hydro energy storage system
cannot be the sole kind of storage system.
Furthermore, suitable locations for a pumped hydro storage system are limited, so
alternative storage systems are desirable. Moreover, utility scale renewable energy
contributions continue to face major barriers that hinder their expansion.
The intermittent nature of solar isolation, wind, and waves make these unreliable energy sou
rces as the power is not always produced when it is needed [1]-[5].
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No. 6
I. Introduction
New Energy Horizons
Opportunities and Challenges
For these reasons, compressed air energy storage (CAES) has been utilized as a substitute
means of load leveling.
CAES are placed near consumers, and near large, small, and micro scale electric power
networks.
In compressed air energy storage, air is compressed, and stored under pressure.
The release of the pressurized air is subsequently used to generate electricity.
This process is most efficiently accomplished in conjunction with a gas turbine, or turbine of
an emergency generator [20].
In this paper, we suggest how to design supply-demand balance strategies for stable
operations under unexpected situations for the NEA-PSI, RESs, and large-scale ESS insertion
in the South Korean power system.
IEEE PES General Meeting 2015, July 26 - 30, 2015
Sheraton Denver Downtown in Denver, CO., USA
II. Future Supply-Demand Strategies
in the South Korean Power System [21]
Fig. 1 represents supply-demand
balance strategies that utilize the
Northeast Asia power system
interconnection, DERs, and ESS in
South Korea. After an NEA
interconnection,
large
reserve
capacities of the interconnected
power system are needed to prepare
for unexpected transmission line
disconnection or connection. As Fig.
1 shows, a future EMS should be
flexible, to include energy resources
and large ESSs in the unit dispatch,
to increase security in the utilization
of renewable energy, storage
systems, and controllable loads to
meet future demands.
No. 7
New Energy Horizons
Opportunities and Challenges
Fig. 1. Northeast Asia power system interconnection and RES+ESS inserted operations in South Korea [20], [21].
IEEE PES General Meeting 2015, July 26 - 30, 2015
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II. Future Supply-Demand Strategies
in the South Korean Power System [21]
No. 8
New Energy Horizons
Opportunities and Challenges
A. ESS Operation Plan in South Korea
Utility-scale renewable energy contributions continue to face major barriers that hinder
expansion.
The intermittent nature of solar energy, wind, and waves mean that are unreliable energy
sources, in the sense that they are not always producing when needed. They are connected in
parallel for the power generation system. In KEPCO, these ESSs are installed on idle capital of
a substation to regulate the frequency. In KPX, they are installed on a generation plant.
In 2014, the capacity of these ESSs will be 50,000 kW, and the installed cost will be 625
hundred million Won. This is the largest capacity in the world. In 2017, the capacity of these
ESSs will expand to 500,000 kW [21].
In particular, spreading frequency-regulated ESSs will increase the efficiency of output of a
coal generation plant by 100%, by taking charge of the present frequency regulation. The
generation facility can reduce cost by operating efficiently.
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II. Future Supply-Demand Strategies
in the South Korean Power System [21]
No. 9
New Energy Horizons
Opportunities and Challenges
Also, it is possible to maintain a high-quality of power and stabilization of the power
output of renewable energy, by quickly responding to power demands.
Sharing the reserve would have technical and economic benefits by reducing the power
plant investment costs, and organizing a strong power system in a blackout.
CAES is a mature storage technology for high-power, long-term load-leveling applications.
CAES is a hybrid technology of power storage and generation.
It operates in the day time by compressor, and provides low cost electricity during the night
or off-peak time, as required for the gas-turbine generation system.
In the past few years, research has been conducted to improve the efficiency of the
turbines and heat transfer mechanisms used to pump and retrieve compressed air [20].
IEEE PES General Meeting 2015, July 26 - 30, 2015
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II. Future Supply-Demand Strategies
in the South Korean Power System [21]
No. 10
New Energy Horizons
Opportunities and Challenges
B. Distributed Generation in South Korea
Figure 2 represents the detailed RES+ESS
inserted operation plans in South Korea.
Currently, the target of renewable
generation in South Korea is 4.4%. On the
electrical side, distributed generation (DG),
called renewable generation, is expected to
reduce energy loss during power
transmission and save energy, by having
optimum sites in power demand areas.
These distributed sources would have
micro gas turbines, fuel cells, wind energy
generators, solar cells, etc., for small-scale
units; and would have combined cycle
units, hydrogen energy, small-size nuclear
reactors, etc., for medium scale units.
Fig. 2. RES+ESS inserted operations in South Korea [9-10].
IEEE PES General Meeting 2015, July 26 - 30, 2015
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II. Future Supply-Demand Strategies
in the South Korean Power System [21]
No. 11
New Energy Horizons
Opportunities and Challenges
However, wind energy has characteristics that differ from conventional energy sources.
Therefore, its impact on the security of the power supply needs attention, due to the
intermittent and random character of this production option. In addition to being variable, it is
also a challenge to accurately predict wind power production on the time scales of interest,
namely for the following day and for long-term planning.
It is possible to concretely forecast, the average wind power density for the whole year;
however, it is impossible to precisely forecast the days or hours with wind. Integrating large
amounts of wind energy into the electric generation mix requires some special considerations.
Since the wind is determined by random meteorological processes, it is inherently variable.
The supply of power from wind turbines is stochastic in nature and the actual power is more
or less proportional to the third power of the wind velocity (from the cut-in wind speed to the
rated wind speed).
The wind output varies seasonally between summer and winter, and variations are also
present on shorter time scales, namely on an hourly basis.
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III. A Scenario-based Power Flow Analysis
considering ESS in South Korea [21]
No. 12
New Energy Horizons
Opportunities and Challenges
We simulated an inter-area power flow for generation/load variation, using the Korea
Electric Power Corporation (KEPCO) power system planning data.
Figure 3 illustrates the power flow and inter-area flow map without a Jeju Island
interconnection, for South Korea in Northeast Asia.
Figure 4 shows a −10% load reduction operation of the renewable power generation output.
Figure 5 shows a +10% load increase in the operation of renewable power generation
output.
Figure 6 represents an inter-area power flow map for ten sections, consisting of the
backbone transmission line of the KEPCO power system in South Korea.
Figure 7 shows the power flow and inter-area flow map with power system interconnection
considering the DERs and ESS between South Korea and Russia in Northeast Asia.
IEEE PES General Meeting 2015, July 26 - 30, 2015
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III. A Scenario-based Power Flow Analysis
considering ESS in South Korea [21]
No. 13
New Energy Horizons
Opportunities and Challenges
Figure 8 shows the power flow and inter-area flow map of the South Korean power system
in the case of interconnection, considering the DERs and ESS, between South Korea and
China in Northeast Asia.
Figure 9 shows the power flow and inter-area flow map of the South Korean backbone
power system in the case of interconnection, considering the DERs and ESS, between South
Korea and North Korea in Northeast Asia.
Figure 10 represents an inter-area power flow map for ten sections consisting of the KEPCO
backbone transmission line with power system interconnection, considering the DERs and
ESS, between South Korea and Japan.
Figure 11 shows a reverse flow after the Japanese power system interconnection, with
directions of 4→7, 9→8, and 8→Japan.
IEEE PES General Meeting 2015, July 26 - 30, 2015
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III. A Scenario-based Power Flow Analysis
considering ESS in South Korea [21]
No. 14
New Energy Horizons
Opportunities and Challenges
IEEE PES General Meeting 2015, July 26 - 30, 2015
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A Scenario-based Power Flow Analysis
considering ESS in South Korea [21]
IEEE PES General Meeting 2015, July 26 - 30, 2015
Sheraton Denver Downtown in Denver, CO., USA
No. 15
New Energy Horizons
Opportunities and Challenges
A Scenario-based Power Flow Analysis
considering ESS in South Korea [21]
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No. 16
New Energy Horizons
Opportunities and Challenges
CONCLUSION
No. 17
New Energy Horizons
Opportunities and Challenges
We have presented supply-demand balance strategies for stable operations under
unexpected situations for the NEA-PSI, RESs, and large-scale ESS insertion in the South
Korean power system.
• A reliable power system depends on the effects on reliability, considering large-scale ESS,
after the system is connected or disconnected. The future smart EMS should be flexible
and include energy resources and ESS into the unit dispatch, to increase efficiency in
utilizing renewable energy, and controllable load to meet future demand.
• Also, the future Korean power system market operation should also have interaction with
the electricity market, which is not possible in the present market operation functions.
• We suggested how to design supply-demand balance strategies for stable operations
under unexpected situations for the NEA-PSI, RESs, and large-scale ESS insertion in the
South Korean power system.
The preliminary considerations mentioned above consist only of scenario-based supplydemand balance strategies and power flow analysis for the situation that includes various
possible power generation resources, such as NEA power system interconnections, RESs, and
large-scale ESS. However, the results of this research may be referred to for use by the
government, for the establishment of a future reliable construction plan in the South Korean
power system.
IEEE PES General Meeting 2015, July 26 - 30, 2015
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No. 18
New Energy Horizons
Opportunities and Challenges
THANK YOU !
IEEE PES General Meeting 2015, July 26 - 30, 2015
Sheraton Denver Downtown in Denver, CO., USA