• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1046-1052
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• 2017

The load on the power grid of South Korea is expected to grow continuously until the late 2020s, and it is necessary to increase the transfer capacity from the Eastern grid to the Seoul-Gyeonggi region by reinforcing the transmission network for the electric power system to remain stable. To this end, the grid reinforcement by two bipole LCC HVDC transmission systems have been considered on account of the public acceptability and high growth of the fault current level, even though an additional 765kV system construction is more economical. Since the probability of the existing 765kV double circuit transmission line trip is extremely low, a dynamic simulation study was carried out to estimate the efficient HVDC capacity able to stabilize the transient stability by utilizing the HVDC overload capability. This paper suggests the application plan to reduce the HVDC construction capacity with ensuring the transient stability during the 765kV line trip.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.125-126
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• 2015

본 논문에서는 전류형 HVDC Thyristor Valve 의 연속운전 시험을 위한 개선된 방식의 합성시험회로를 제안한다. 제안하는 방식은 기존의 저전압 대전류원 회로에 단상 풀-브리지 인버터를 적용하여 회로를 간소화 하였고, 이전보다 간단한 방법으로 보조 사이리스터 밸브를 턴-오프 한다. 제안하는 방식에 대한 구간별 동작 원리를 설명하고, 타당성을 검증하기 위해 시뮬레이션 분석과 축소모형 실험을 실시하였다.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1920-1929
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• 2018

In order to provide a source for nine phases suitable for 18-pulse ac to dc power, this paper proposes a new structure for a step-up asymmetrical delta-connected transformer for converting three-phase ac power to nine-phase ac power. The design allows for symmetry between the nine output voltages to improve the power quality of the supply current and to minimize the THD. The results show that this new structure proves the equality between the output voltages with $40^{\circ}-{\alpha}$ and $40^{\circ}+{\alpha}$ phase shifting and produces symmetrical output currents. This result in the elimination of harmonics in the network current and provides a simulated THD that is equal to 5.12 %. An experimental prototype of the step-up asymmetrical delta-autotransformer is developed in the laboratory and the obtained results give a network current with a THD that is equal to 5.35%. Furthermore, a finite element analysis with a 3D magnetic field model is made based on the dimensions of the 4kVA, 400 V laboratory prototype three-phase with three-limb delta-autotransformer with a six-stacked-core in each limb. The magnetic distribution flux, field intensity and magnetic energy are carried out under open-circuit operation or load-loss.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.898-902
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• 1998

Voltage and harmonic stability characteristics of capacitor commutated converters applied to a BTB (back to back) system (CCC-BTB) are analyzed and compared to characteristics of a BTB system composed of conventional line commutated converters (LCC-BTB). About 1.6 times larger safe operating regions can be obtained for the CCC-BTB system compared to the latter. The CCC-BTB system results in no harmonic instability problem as it has no shunt reactive compensators in the station and the adjoining AC system generates no low anti-res onance points.