Scholarly article on topic 'Design and Analysis for SFCL Combined System Utilizing On-line Electric Vehicle'

Design and Analysis for SFCL Combined System Utilizing On-line Electric Vehicle Academic research paper on "Electrical engineering, electronic engineering, information engineering"

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{"SFCL utilization" / "Distribution network protection" / "Electric vehicles" / "Inductive system" / "Wireless charging"}

Abstract of research paper on Electrical engineering, electronic engineering, information engineering, author of scientific article — S. Jung, G. Jang

Abstract The various concepts of the wireless power transportation system have been already studied including the efficiency and harmonics issue as well as system stability. This paper deals with a utilizing process about superconducting fault current limiter (SFCL) at the distribution level to prepare the fault condition of the nearby system with On-Line Electric Vehicle (OLEV), which is designed using the resonance support system. These inductive power conversion systems are being considered to build closely to utility grid because the charging system could generate low voltage condition. Therefore, adoption of the current limiter on the system can be a possible solution to the terminal distribution system. Furthermore, the OLEV system utilizes resonance charging system which can respond fault condition immediately with segregated state. In this paper, combined SFCL system is introduced to solve the fault current issue under the low voltage distribution system by using the concept of the proposed OLEV and SFCL. The algorithm for the charging system of electric vehicles has been set for the examination of several operating condition, including default status.

Academic research paper on topic "Design and Analysis for SFCL Combined System Utilizing On-line Electric Vehicle"

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Physics Procedia 65 (2015) 273 - 277

27th International Symposium on Superconductivity, ISS 2014

Design and analysis for SFCL combined system utilizing On-Line

Electric Vehicle

S. Junga, G. Janga*

aSchool of Electrical Engineering, Korea University, Seongbuk, Seoul, 136-713, Korea

Abstract

The various concepts of the wireless power transportation system have been already studied including the efficiency and harmonics issue as well as system stability. This paper deals with a utilizing process about superconducting fault current limiter (SFCL) at the distribution level to prepare the fault condition of the nearby system with On-Line Electric Vehicle (OLEV), which is designed using the resonance support system. These inductive power conversion systems are being considered to build closely to utility grid because the charging system could generate low voltage condition. Therefore, adoption of the current limiter on the system can be a possible solution to the terminal distribution system. Furthermore, the OLEV system utilizes resonance charging system which can respond fault condition immediately with segregated state. In this paper, combined SFCL system is introduced to solve the fault current issue under the low voltage distribution system by using the concept of the proposed OLEV and SFCL. The algorithm for the charging system of electric vehicles has been set for the examination of several operating condition, including default status.

© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the ISS 2014 Program Committee

Keywords: SFCL utilization; Distribution network protection; Electric vehicles; Inductive system; Wireless charging

1. Introduction

To find an appropriate solution to high energy consumption, many industrial fields consider the technical applications of the use of high efficiency power transfer system in terms of realistic structure. In addition, emissions of carbon dioxide and higher gasoline prices lead to concerns in the power utilization. The high frequency basis inductive power transfer system (IPTS) to compose the contactless electric charging infrastructure has been developing. Among the various IPTS application, an electric vehicle (EV) is one of the most efficient types of equipment. Moreover, a public transportation system applying EV technology has certain moving characteristics and power consumption pattern depending on the vehicle operating schedule which is suitable to composing a charging and discharging plan [1].

However, when we configure IPTS basis EV charging system in the power grid, further considerations regarding not only voltage variation but also protection scheme analysis are required. Especially, since the expected installation site of charging system is at the front of the distribution transformer because of its power consumption pattern, the fault protection scheme is to be one of major issue. An analyzing process about suitable distribution network has been progressed by adopting DC resistive superconducting fault current limiter (SFCL) in presented paper [2]. The opportunities and availability of superconducting coil were checked but the economic feasibility should be dealt with

* Corresponding author. Tel.:+82-10-3412-2605; fax: +82-2-3290-3692. E-mail address: gjang@korea.ac.kr

1875-3892 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the ISS 2014 Program Committee

doi:10.1016/j.phpro.2015.05.149

available option, and hybrid designed system is able to be the solution in such a small distribution network. To achieve this, system design and application effect should be performed firstly through verified case studies. Additionally, since the utilized IPTS is being considered as a sensitive power device, the SFCL application should deal the relay coordination regarding protection scheme. These interactions between protective devices and SFCL were previously presented focusing relay coordination, and the theory was applied in the proposed simulation studies [3].

This paper proposes the design of SFCL application in the On-Line Electric Vehicle (OLEV) system so as to prepare fault condition which frequently occurs in the distribution system. The process to apply SFCL to the designated wireless transfer system is mainly discussed and the simulation results are analyzed in this paper.

2. System description

2.1 IPTS installation

The IPTS charging system in this paper utilizes 22.9 kV AC supplied from the grid and performs the conversion process of the AC/DC/AC with own IGBTs. The transferred AC power at the terminal section is on the ultra-high frequency state for charging the battery through wireless charging method, and it leads a structural separation between each section.

As a transportation system, the IPTS should be composed in both side of the road and the distance from the IPTS to the substation cannot be lengthened due to the voltage issues. Fig. 1 shows a simplified image of the proposed system with the power distribution network. To protect each section including the IPTS, circuit breakers (CBs) are composed at the designated point. The required power by two distribution systems composed with a 30 MVA load are supposed to be supplied through one high voltage transmission network. When constructing IPTSs in the distribution network, the appropriate location for the system would be the point between the distribution transformer of high voltage substation and the bus to divide each phase to certain load.

The both side of IPTS supply charging current individually when the vehicle reaches the charging platform. The required power is transferred directly through connected transformer and normally the link between each distribution bus is prohibited due to relay coordination [4]. The proposed system considers the support mode during fault condition for other distribution network through utilizing inductive linkage by IPTSs. The single phase fault is designed at Bus A as shown in the Fig. 1.

TB, 25MVA Bus B - 22.9 kV

Fig. 1. Distribution network with IPTS system

2.2. OLEV characteristics

As the adopted battery in the vehicle is comparatively low, instantaneously high power is required during the IPTS operation. And since the OLEV has adopted the low-speed charging mode, the IPTS configuration is suitable for converting the operation mode to other inductive resource. The OLEV system is being performed utilizing an IPTS for generating a 20 kHz ultra-high frequency voltage through own IGBT devices [5].

Based on the previous research, the IPTS operation in this paper is assumed to repeat the charging process at specific interval with the designated headway by system operator. Without vehicle, the IPTS can perform other ancillary service with own voltage source converter; SFCL application was proposed to handle fault condition by focusing on these point.

3. SFCL application

As the various application of SFCL to improve power system condition is progressed, current researches are being focused on not only preventing high fault current but also offering a solution about power quality issues [6]. Among the

--- Substation nearby ^ Local load

Fig. 2. Schematic operation of proposed system

Fig. 3. Concept of switchable mode of proposed system

Convenor Current rcgultor Rectifier

Fig. 4. Circuit map of proposed system in SFCL operation mode

SFCL applications, strict voltage support about SFCL with ultra-high frequency can be utilization in the OLEV system through own power conversion method. Fig. 2 represents the operational plan of the proposed system. The platform is designed to convert from general state to voltage-support mode for supporting other system when EVs do not exist in own system. The operation mode of both side's IPTS can be changed as represented in Fig. 3.

Fig 4 represents the circuit of the proposed system at SFCL operating mode. It is mainly composed with several IGBT devices (G1-G10) in converter and regulator section for configuring IPTS to generate ultra-high frequency AC current. DC capacitors (Ci-C2) are composed to maintain the voltage during the SFCL operation mode. The transformer of grid port (Ta, Tb, Tc) is linked with the main distribution network which is for charging platform. The transformer in rectifier section (Ta', Tb', Tc') is linked with the others distribution network regarding FCL port. The SC coil is located in the rectifier section and interwork automatically to limit the current through the three series rectifiers (D1-D12). When the fault occurs on the target section, the SC coil is introduced directly and the current regulator is set up to absorb the energy of the system and the superconducting coil. The energy is transferred by assigning the DC voltage at the capacitor through the regulator.

4. Simulation

The mentioned distribution system is utilized in the simulation studies. The specifications of the distribution system are summarized in Table 1. It is assumed that the SFCLs are installed in the OLEV system and the data required for the simulation are shown in Table 2. The main purpose of the simulation is verifying the effectiveness about SFCL as a current limiter for distribution system and checking the ability regarding own protection scheme by delaying the operation of CB near the IPTS with appropriate system condition.

Table 1. Specifications of the distribution system

Utility grid 154 kV, 15 SCR, 15 (X/R)

Transformer (TA,TB) 154/22.9 kV, 25 MVA, j 10%

Line Impedance (95 SQMM) Z= 0.21+j0.2523/km

_ , , . Line 1 - 8 km

Feeder length Line 2,3 - 4 km

Fault location Bus A, Line 1

Table 2. Numerical data of the performed simulation

Rated Current Min. fault Current System voltage DC Voltage Load/ phase Saturated Inductance Tsfcl Tbreaker Rcb Zfault Max. Integral tsim theadway

0.78 1.25 22.9 1.5 10 0.2 0.01 0.03 0.1 0.02 + 50 1 130

[kA] [kA] [kV] [kV] [MW] [mH] [s] [s] [O] j0.012 [sec] [sec]

Fig. 5. Voltage and current waveforms of phase A (without SFCL)

Fig. 6. Voltage and current waveforms of phase A (with SFCL)

I ✓ Integral value (limit : 50)

Withoutj SFCL /

/ ^^ With SFCL

0 160 550

Fig. 7. Integration value for trip signal of CB (Bus A)

Time (ms)

For comparison with the normal operation, voltage and current waveforms during the fault are displayed separately. Fig. 5 shows the waveforms of phase A at fault condition. The CB is opened promptly without reserve interval for OLEV operation. In case of this situation, the operator cannot manage the vehicle operation plan owing to the lack of the spare time and the low voltage problem. The impact should be restricted for not only protecting distribution system but also maintaining the sensitive power electronic devices. In the Fig. 6, the CB operation is delayed with more suitable condition for the system operator in terms of voltage issue. Since the proposed SFCL utilizes SC coil and generates power transfer about required quantity through the IPTS, a relatively long inductive transient states were generated. However, the entire fault current and regarding voltage drop were limited with the proposed SFCL.

The comparison about integration values for trip signal of CBs is represented in Fig. 7. As seen in Figure, the trip signal from over current was delayed with SFCL. The tripping time of the CB with SFCL could be seen to be delayed almost 0.4 seconds compared with the normal operation case. The charging system is composed by power electronic devices and generally considered as protective device. The result shows that the hybrid system would offer more appropriate management condition to the system operator by implementing prevention of fast trip from the power system with reduced fault current flow.

5. Conclusions

This paper suggests the SFCL application on the designed OLEV system to regulate fault current in the distribution network. The novel circuit is proposed for composing hybrid system with IPTS. The adopted OLEV system has suitable characteristics for managing SFCL with own contactless transfer configuration. The first target of proposed system is fault current reduction for terminal distribution system, and this ability was verified through designated distribution network. A single ground fault which is usually issued in the distribution system could be protected efficiently with the proposed system. At the same time, it is required to IPTS for protecting power electronic devices against grid fault, and the proposed system includes the conceptual solution by focusing on its transportation characteristic composing the platform at the both sides of the distribution network.

The case study indicated that the proposed system producing the capability for limiting the fault current in single fault condition, and generating adequate option for managing the devices to system operators. The EMTDC analyzing for the protection coordination of CBs was progressed.

Acknowledgements

This work was supported by the NRF grant (No. 2013H1A2A1034289) and by Human Resources Development of KETEP grant (No. 20114010203010) funded by the Korea government.

References

Reference to a journal publication:

[1] Seungmin J., Hansang L., Chong Suk S., Jong-Hoon H., Woon-Ki H., Gilsoo J., "Optimal Operation Plan of the On-Line Electric Vehicle System through Establishment of DC Distribution System," IEEE Trans. Power Electronics, 28, 2013, 5878-5889.

[2] Morandi A., Imparato S., Grasso G., Berta S., Martini L., Bocchi M., Fabbri M., Negrini F., Ribani P. L., "Design of a DC Resistive SFCL for Application to the 20 kV Distribution System," IEEE Trans. Applied Superconductivity, 20, 2010, 1122-1126.

[3] Sung-Hun L., Jin-Seok K., Jae-Cul K., "Analysis on Protection Coordination of Hybrid SFCL With Protective Devices in a Power Distribution System," IEEE Trans. Applied Superconductivity, 21, 2011, 2170-2173.

[4] Girgis A., Brahma S., "Effect of distributed generation on protective device coordination in distribution system," in Power Eng. Large Eng. Syst., Halifax, NS, Canada, 2001. 115-119.

[5] Choi Y., Kang D., Lee S., Kim Y., "The autonomous platoon Driving system of the On Line Electric Vehicle." ICROS Conf., Int. Joint Conf., Japan, Aug. 2009.

[6] Zhao C., Wang Z., Zhang D., Zhang J., Du X., Guo W., Xiao L., Lin L., "Development and Test of a superconducting Fau lt Current Limiter-Magnetic Energy Storage (SFCL-MES) System," IEEE Trans. Applied Superconductivity, 17, 2007, 2014-2017.