Harmonic Analysis Model Based on 8-port Representation for Korean High Speed Railway

Transcription

1 Harmonic nalysis odel ased on 8-port epresentation for Korean High Speed ailway Kwanghae Oh* Hanmin Lee* Sanghoon hang* * : lectric Power Lab, Korea ailroad esearch nstitute, Woulam-ong, Uiwang-ity, Kyonggi-o, South Korea bstract - his paper proposes a new model for harmonic analysis in _5k traction power supply system including inverted feeder, contact line, rails and auto-transformer. he system model is based on four-port representation which is an extension of two-port network theory. n order to verify the proposed approach, we have analysed and tested real traction power feeding system focused on the amplification of harmonic current. he calculation results from the proposed approach and the measurement data from the test are widely described in the paper.. ntroduction odern electric car has thyristor or PWPulse Width odulation-controlled converters, which give rise to higher harmonics. he current harmonics injected from electric car is propagated through power feeding circuit. s the feeding circuit is a distributed constant circuit composed of L, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. he magnified current harmonics usually brings about various problems. hat is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. urthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. herefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. rom these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. he system model is based on 8-port representation which is an extension of -port network theory. 8-port representation for each component of the system has many advantages : Overhead catenary lines which have mutual impedances as well as series impedances and shunt admittances can be easily represented by an equivalent 8-port model with appropriate circuit parameters. istributed circuit parameters for the line model can be defined. 8-port representation makes it possible to obtain the relationship the currents and the voltages for an auto-transformer with mid-point connected to the rails. 3 he entire system can be easily modeled by the combination of 8-port representation of each component in parallel and/or series. Harmonic calculation can be performed straightforwardly. he proposed algorithm is applied to a real uto-transformer-fed system in which electric car with thyristor-controlled converters is running. n order to verify the proposed approach, we have analysed and tested real traction power feeding system focused on the amplification of harmonic current. he calculation results from the proposed approach and the measurement data from the test are widely described in the paper.. odeling and ormulation. Harmonic ircuit odel for raction Power eeding System he usual feeding systems of electrification are based on single phase 5 k/5 k. he feeding system is connected to three-phase power system to be supplied with large single-phase load. feeding circuits supply vehicles with the power by 3 to phase Scott transformer through feeder, contact wire and rail as shown in ig. uto- transformers are installed about every ten kilometers with circuit breakers which connect adjacent up and down tracks at sub-sectioning postssp. Substations SS are located every fifty kilometers and there is a sectioning postsp midway between two substations. SP has circuit breakers which enable one feeding circuit to electrically separate from the other. hey may be closed in case adjacent SS is out

2 of service. Now let source impedance be ss and traction vehicle be harmonic current source on the side of phase or. ig. raction Power eeding System. ormulation by 8-port epresentation n a general way, it is desirable harmonic analysis should be performed on two-port representation for the sake of calculational convenience. Harmonic current source is, however, connected to contact line and rail conductor on secondary sides of two s which of primary terminals are connected between contact line and inverted feeder in the circuit model as shown in ig. What is more, there are capacitive admittances among three conductors contact line, inverted feeder and rail conductor. hey make it impossible to realistically model the traction power feeding system upon two-port representation. or that reason, this paper proposes a new model for harmonic analysis in the traction power supply system including inverted feeder, contact line, rails and auto-transformer. he system model is based on four-port representation which is an extension of two-port network theory. our-port representation for each elements in the electrified railway system can be derived as follows : he odelling of a uto-transformer n auto-transformer at SP connected to the overhead catenary line in parallel may be modelled as shown in ig. ig. quivalent circuit of uto-transformer for SP

3 he relationship between voltages and currents for at the end of the linesp can be derived as equation. he equivalent circuit of an auto-transformer at SSP is shown in ig 3. ig 3. quivalent circuit of uto-transformer for SSP On the basis of ig 3, it is possible to obtain the relationship between voltages and currents for an autotransformer at SSP. Overhead atenary lines Overhead catenary lines have not only their self and mutual impedances but also shunt admittances. quivalent -type model for an overhead catenary line section can be represented with these parameters as shown in ig.

4 ig. quivalent -type model for an overhead catenary line section he voltages and currents of the sending end for each block/ can be expressed in terms of the receiving end quantities by: 3 or the middle block, the voltages and currents of the sending end are obtained as follows : herefore, the relationship for voltage and currents can be rearranged as equation 5 / / 5 3 Harmonic urrent Source harmonic current source in electrified railway system is, mainly, traction car, which can be considered as a harmonic current source injected from rail to contact line as shown ig 5.

5 ig 5. Harmonic urrent Source rom this point of view, 8-port model for harmonic current due to traction car is represented as equation 6. H H 6 he odelling of a substation he equivalent circuit of phase or for a substation with an auto-transformer is shown in ig 6 and ig 7. Where s implies the impedance of main transformer and power utility. ig 6. quivalent ircuit odel for Power Utility and ain transformer at SS

6 ig 7. quivalent ircuit odel for uto-transformer at SS he 8-port model of equivalent circuit for the auto-transformer is represented as equation 7. Where, 7 ssuming s to be purely sinusoidal 6Hz voltage source, s become [] for harmonic analysis. 3. Harmonic nalysis ocused on the amplification of harmonic current, harmonic analysis for traction power feeding system will be described in this section. or analysis, 8-port model obtained in section is used for harmonic analysis. Now, the entire system can be easily modeled by the combination of ight-port representation of each component in parallel and/or series. herefore, following equation will result as follows.

7 SS SS H H SSP 8 SP 8 8 he oltage and current at SP can be obtained from equation 8. n like manner, the voltage and current at any point of the line can be calculated straightforwardly.. ase Studies. nput ata real traction power feeding system in reference [3] was used for the test system. he detail data can be found in the reference.. esults n order to verify the proposed approach, we have analysed and tested real traction power feeding system focused on the amplification of harmonic current. he harmonic current through into SS is shown in ig 8. rom ig 8, it is observed that the measured harmonic current is very close to the estimated result by the proposed approach. ig 8. agnification of urrent Harmonics ig 9. illustrates the impact of the catenary model on the result. he comparison have been performed between the results: section ; sections ; 3 sections ; more than sections of quivalent -type model for an overhead catenary line. here are more differences in result as harmonic order is increased in case of section and sections of quivalent -type model. herefore it is desirable to use more than sections of quivalent -type model for an overhead catenary line. s a result, the resonance frequency is about 5[Hz] and the magnification of harmonic current is about 6.5[pu].

8 ig 9. he mpact of the atenary odel on the esult ig. illustrates the harmonic current vs. location of vehicle. he resonance frequency is not depend on the location of vehicle as shown ig. he magnification of harmonic is, however, a function of the position of a train. he farther is the train from the substation, the magnification of harmonic current is higher. hese results are similar to those of reference [] and give a basis that - bank should be installed at SP. ig. shows correlation between catenary length and harmonic esonance. rom the result, he resonance frequency is lower as catenary length is longer. ig. agnification of urrent Harmonics as a unction of the Position of a rain

9 ig. orrelation between atenary Length and Harmonic esonance 5. onclusions this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. hrough the research we can conclude the following: t is desirable to use more than sections of quivalent -type model for an overhead catenary line. he resonance frequency is not depend on the location of vehicle. he magnification of harmonic is, however, a function of the position of a train. 3 he resonance frequency is lower as catenary length is longer. eferences [] oshifumi ochinaga, Higher Harmonics esonance on eeding ircuit and ountermeasures to Suppress it,. Japan, ol. -, No., 99 [] Joachim Holtz and Heinz-jurgen Klein, he Propagation of Harmonic urrents Generated by nverter-ed Locomotives in the istributed Overhead Supply System, ransactions on Power lectronics, ol., No., 989 [3] Korea ailroad esearch nstitute, valuation of Power Quality and ts ountermeasure n Seoul-aejeon High-speed ailway, 999 [] odeling and simulation of the propagation of harmonics in electric power networks P _, ransactions on Power elivery, ol, No, January 996 [5] odeling and simulation of the propagation of harmonics in electric power networks P _, ransactions on Power elivery, ol, No, January 996