Physica C 471 (2011) 1290–1294

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Physica C

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Power system analysis of Hanlim superconducting HVDC system using realtime digital simulator

Y.J. Won a, J.G. Kim b, A.R. Kim b, G.H. Kim b, M. Park b, I.K. Yu b,⇑, K.D. Sim c, J. Cho c, S. Lee d,K.W. Jeong a, K. Watanabe e

a Korea Electric Power Corporation, Yongdong-dearo, Seoul 135-791, Republic of Koreab Changwon National University, 9 Sarim-Dong, Changwon 641-773, Republic of Koreac Superconducting Device and Cryogenics Group, Korea Electrotechnology Research Institute, Changwon 641-120, Republic of Koread Uiduk University, Gangdong, Gyeongju 780-713, Republic of Koreae HFLSM, Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

a r t i c l e i n f o

Article history:Available online 26 May 2011

Keywords:DC power cableHigh temperature superconducting cableLoss characteristicHVDC

0921-4534/$ - see front matter � 2011 Elsevier B.V. Adoi:10.1016/j.physc.2011.05.180

⇑ Corresponding author. Address: 55315, Changwonwon 641-773, Republic of Korea. Tel.: +82 55 281 31

E-mail address: yuik@changwon.ac.kr (I.K. Yu).

a b s t r a c t

Jeju island is located approximately 100 km south from the mainland of Korea, and had a peak load ofabout 553 MW in 2008. The demand increases 7.2% a year over the last 5 years. Since the wind profilesof Jeju island are more favorable than mainland of Korea, many companies have shown interest in thewind power business at the Jeju island. Moreover KEPCO has a plan for renewable energy test too whosepower will be delivered by HVDC system. One kilometer length of total 8 km was designed as supercon-ducting DC cable. Rest 7 km will be the conventional overhead line. In this paper, the authors have devel-oped a simulation model of the power network around 8 km HVDC system using real time digitalsimulator (RTDS).

� 2011 Elsevier B.V. All rights reserved.

1. Introduction

Jeju island is the largest and tourist island in Korea, locatedapproximately 100 km south from the mainland, and had a peakload of about 553 MW in 2008. The demand increases 7.2% everyyear over the last 5 years. The power network in Jeju island con-sists of three power plants with 154 kV of 360 km lines. Thesepower plants are comparatively smaller and generation cost ismuch higher than those on the mainland. To meet the increasingdemand and preserve the environment of Jeju, HVDC transmissionsystem has linked between Haenam on the mainland and Jeju with100 km submarine cables. The HVDC system provides the highquality power of the mainland and avoids the difficulty of securinggeneration sites. The peak load of Jeju island is 553 MW, which in-cludes capacity of 300 MW through the HVDC from the mainland.Consequently the real power transmission is about 50% of the totalpreserved in the island [1–3].

Since the wind profiles of Jeju island are more favorable thanmainland of Korea, many companies have shown interest in thewind power business at the Jeju island. The approved wind powercapacity reaches 250 MW, about 40% of total generation capacity ofJeju power system. However, the installation of wind turbines in a

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weak, small, isolated Jeju power system may cause some expectedproblems [4].

However, fluctuations in output power from the renewable en-ergy systems may be a cause for concern and may result in insta-bility to the electric power system. This means that theintroduction of HVDC links will be increased in the renewablesource-based AC power systems.

Superconducting cables utilize superconducting materials in-stead of the copper or aluminum traditionally used for overheadpower lines and underground cables. Superconductor materialscan carry well over 100 times of the current density of copper oraluminum, which in turn drives system economically and is funda-mental to the reason why superconductor DC cables comparefavorably with conventional alternatives for long distance powertransmission. Secondly, when transmitting DC power, supercon-ductors become perfect conductors with zero electrical resistanceand introduce no electrical losses of their own [5–9].

KEPCO has planned to construct a test site for renewable energyin Jeju power system near Hanlim area. Fig. 1 shows the locationand configuration of the Hanlim C/S (converter station). It will belocated at 8 km distance from Hanlim substation and be connectedto the conventional 154 kV AC transmission line. In addition, 80 kVclass 8 km HVDC system is also planned to set up between Hanlimsubstation and Hanlim converter station in 2014. Among 8 kmlength, 7 km will be general overhead line and 1 km DC power linewill be installed with HTS DC power cable.

Fig. 1. 154 kV Jeju power network and detail grid view of Hanlim area.

Fig. 2. Current power system diagram near Hanlim substation (2010).

Fig. 3. Power system with superconducting DC cable near Hanlim substation (2014).

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Fig. 4. Configuration of Hanlim HVDC system including 1 km HTS DC cable.

Fig. 5. Modeling of Hanlim substation and HVDC system using RTDS/RSCAD.

Table 1System specifications of simulation system.

Hanlim HVDC AC network

DC voltage 80 kV Gas turbine #1 45 MW (Hanlim S/S)DC current 750 A Gas turbine #2 45 MW (Hanlim S/S)Main transformer 154/34.2 kV 30 MVA Steam turbine #1 45 MW (Hanlim S/S)Xc 0.12 Wind farm 20 MW (Hanlim C/S)

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This paper analyses the power flow of the 154 kV networkaround Hanlim S/S and C/C in Jeju island using real time digitalsimulator (RTDS).

2. Hanlim HVDC system

Before install the superconducting DC cable in real power sys-tem, simulation test is strongly needed for system stability analy-sis. In this research, configurations of superconducting cable werenot considered because the specifications of Hanlim HVDC systemare not decided yet. Just transmission line parameters of 1 kmsuperconducting cable are considered for simulation. Resistanceis zero, inductance and capacitance value was considered as JejuHVDC #1 cable.

The configuration of current power system of Hanlim S/S isshown in Fig. 2. Hanlim combined cycle power plant (C/C) is con-nected to the Hanlim substation (S/S). Hanlim S/S is connected toSinjeju and Anduck S/S using 154 kV AC transmission line.

Hanlim C/S will be the new facility which will install severaltens MW wind farm between Hanlim and Sinjeju substation. Sys-tem configuration in 2014 is described in Fig. 3. There will betwo transmission lines between Hanlim C/S to Hanlim S/S,154 kV class AC overhead line and 80 kV class HVDC line. The out-put power from Hanlim C/S will be delivered via Hanlim 80 kVHVDC system of which detailed configuration is shown in Fig. 4.Total length of HVDC transmission line is designed as 8 km. It con-sists of two components, one is the 7 km length overhead line andthe other is 1 km superconducting DC cable. Each ends will be con-nected via the overhead and underground termination facility.

Fig. 6. Seven kilometer overhead DC line and 1 km superconducting cable system in RTDS/RSCAD.

Y.J. Won et al. / Physica C 471 (2011) 1290–1294 1293

Rated current of Hanlim HVDC system is 750 A. Relation betweenAC and DC voltages are as follows:

Vd ¼3ffiffiffi

2p

pVl cosðaÞ � 3

pXcId; ð1Þ

where Vd is DC voltage, Vl is AC voltage, Xc is leakage reactance oftransformer, Id is DC current and a is firing angle. Thus transformerratio is decided to 154/34.2 kV for 80 kV DC voltage under 15� firingangle. In case of current source type HVDC converter, two trans-formers, Y–Y and Y-delta are connected in series to reduce thelow order harmonic.

Fig. 8. Power flow variation caused by wind power fluctuation.

3. Modeling and simulation of Hanlim HVDC system

RTDS is a power system analysis simulator and it can simulatein real time which is the strong point of view when power analysissimulation. Introduced power system of Hanlim area is modeledwith the detail components in RTDS. Modeling of Hanlim substa-tion and HVDC system using RTDS/RSCAD is depicted in Fig. 5.The modeled system includes three 154 kV substations and twopower plants whose specifications are summarized in Table 1.Hanlim C/C has three generators which are 45 MW each. NamjejuT/P (thermal plant) consists of two thermal generators and fourdiesel generators. 20 MW squirrel cage induction generator modelis connected to the Hanlim C/S. Moreover, 120 MW loads are con-nected into the Sinjeju and Anduck S/S. The detailed configurationof superconducting HVDC system is shown in Fig. 6. In thissimulation, superconducting power cable resistance was zero,inductance and capacitance is considered as conventional copper

Fig. 7. Transient power flow characteristics when HVDC starts.

cable according to the data obtained from Jeju–Haenam HVDCsystem.

Fig. 7 is the variation of power flow when Hanlim HVDC systemwas operated. Rated power of HVDC system in this simulation was30 MW. Only power flow of Hanlim C/S to Sinjeju S/S transmissionline was increased by HVDC operation. In this case, wind farm wasnot connected to the Hanlim C/S.

The simulation results for wind farms are shown in Fig. 8.Transmission power of all AC networks are changed by variationof wind power. The output of wind farm was changed by windspeed data in RTDS and AC networks were influenced directly.

Fig. 9. DC current and voltage of superconducting HVDC system in Hanlim C/S.

1294 Y.J. Won et al. / Physica C 471 (2011) 1290–1294

However, the power flow of HVDC transmission line was not af-fected by variation of wind power because power flow of HVDCtransmission system can be controlled. In this simulation rectifieroperated for constant DC current and inverter was operated forconstant DC voltage. Detail simulation results of DC current andvoltage are shown in Fig. 9. DC current includes 12 pulse rippleby thyristor converter according as DC side voltage and currentwere affected by number of thyristor.

4. Conclusions

The stability of Jeju power system will be influenced by super-conducting HVDC transmission system and increasing of windpower generation system in 2014. The authors have developed Jejuisland power system and 80 kV Hanlim HVDC with 1 km supercon-ducting DC cable model using RTDS. Power flow of Hanlim area isanalysed by simulation using real time digital simulator. Powerflow between Hanlim to Sinjeju transmission line was increasedup to 5 MW after HVDC system start. Otherwise the power flowof other transmission line was decreased. Variation of wind poweraffected to the power flow of AC transmission line, but HVDC linewas not affected by wind power variation.

Acknowledgments

This work was supported by a grant from the Center for AppliedSuperconductivity Technology of the 21st Century Frontier R&DProgram, funded by the Ministry of Education, Science and Tech-nology, Korea and also supported in part by Institute for MaterialsResearch, Tohoku University, Japan.

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