IEEE Power & Energy Magazine - May/June 2019 - 67

the island will require the capabil-
ity of transmitting power back to
the bulk power system, as shown in
figure 6. therefore, hVdc num-
ber 3, which is in the planning stage,
must be flexible and bidirectional.
it is most likely to be an mmC-based
VsC scheme.

Mainland

Mainland
HVdc 1
LCC HVdc

HVdc 2
LCC HVdc

Mainland
HVdc 3
MMC HVdc

Expected
Wind Farm

Feasibility Studies for Jeju
HVdc Number 3

since 2010, kepCo has conducted
numerous feasibility studies for
Jeju hVdc number 3. kepCo first
needs to determine the type of
Jeju Island
hVdc (lCC or mmC). regarding
power-reversal capability, mmC-
figure 5. A simplified power system representation of Jeju Island.
hVdc is more flexible than lCC-
hVdc and has less negative influ-
ence on the operation and reliability of the Jeju power system. that kepCo can reduce the cost of purchasing power with
the feasibility studies address key issues that include active the addition of the mmC-hVdc for hVdc number 3. how-
power reserve, reactive power compensation, escr, multi- ever, the mmC converter station costs are higher than those
infeed escr, effective inertial constant, hosting capacity of for lCC. therefore, kepCo determined the type of hVdc
renewables, and tsA. in particular, lCC-hVdc requires must- based on the results of the economic and technical feasibil-
run synchronous generator operation to maintain a suitable ity studies, and mmC-hVdc was chosen for hVdc number 3
short circuit availability, and this constraint reduces the host- because of the flexible power transfer capability.
ing capacity for the renewables. An emt study determined the
power reversal procedure and its influence on the Jeju power Technical Challenges for the Jeju Power System
system. Although mmC-hVdc would not need any additional the future Jeju power system, which includes a high pen-
controls, lCC-hVdc requires many steps to reverse the power etration of renewable energy sources, will encounter many
transfer. Application of lCC-hVdc requires the use of a mass- technical challenges with multi-infeed (multiple hVdc sys-
impregnated dc cable and a converter transformer with high tem installations) and hybrid-infeed (different types of hVdc
insulation levels to cope with the dc voltage polarity change converter stations) hVdc systems located electrically close
during the lCC-hVdc power reversal.
to each other in an area with low scr and inertia. the mas-
An economic feasibility study was conducted. when sive penetration of wind power generation could threaten
hVdc number 3 is installed, and the penetration of the the stability performance of the Jeju power system. the
renewable energy source increases on Jeju, the island's sys- two lCC-hVdc systems require reactive power compensa-
tem marginal price (smp) can be significantly reduced; the tion for power transfer. overvoltage conditions may occur
smp with the addition of the mmC-hVdc would be lower during ramp-down and recovery operations. transient volt-
than that with the addition of an lCC-hVdc tie. this means age depression may also occur because of the simultaneous

Expected Power Mix 2029 in Jeju

2,219 MW
(67%)

HVdc
LNG

200 MW
(6%)
312 MW
(9%)

Thermal
Renewable

Capacity (MW)

600 MW
(18%)

Expected Renewable Power Capacity Versus Peak Demand in Jeju
2,500
2,000
1,500
1,000
500
0
2016

2018

2020

2022

2024

2026

2028

2030

Year
Peak Load

Renewable

figure 6. Future capacity (nameplate) on the Jeju Island power system. LNG: liquefied natural gas.
may/june 2019

ieee power & energy magazine

IEEE Power & Energy Magazine - May/June 2019

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2019