TECHNOLOGICAL DEVELOPMENT OF THE IGBT APPLIED 3 LEVEL CONTROLLED

CONVERTOR SYSTEM FOR THE SHINKANSEN HIGH-SPEED TRAIN

Sakae ISHIKAWA, General Manager

Junichi ITO, Manager

Masayuki UENO, Assistant manager

Yoshiyasu HAGIWARA, Assistant officer

Central Japan Railway Co., Tokyo, Japan

Telephone: +81-3-3217-0285

Facsimile: +81-3-3212-1383

Summary:

For the next generation of the high-speed train, Central Japan railway company (JR Central) has developed the IGBT applied innovative traction system. IGBT has an advantage of higher switching frequency and fine control characteristics, so this system can realize reduction of noise and higher harmonics from the train.

JR Central took the running test of the innovative IGBT convertor system. As a result, reduction of noise and higher harmonics was assured and the total quality of the high-speed train, such as light weight, low heat-loss, high efficiency and reliability, low maintenance work, and low price, was highly improved.

JR Central plans to apply this IGBT traction system to the new generation high-speed train, series 700, which will launch in Autumn in 1997.

Key words: traction system, IGBT, GTO thyristor, noise reduction, higher harmonics

1. Introduction

To pursue improvement of service quality by speed-up of the high-speed trains, Central Japan railway company (JR Central) had developed series 300 Shinkansen train, which applied AC drive system first in high-speed trains in Japan, and realized 270kni1h operations between Tokyo and Shin-Osaka in 1992.

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After the Series 300 appeared, AC drive system and AC regenerative brake system became the standard traction system of the Shinkansen high-speed train in Japan. Large-volumization of the GTO thyristor in the second half of the 1980s had contributed to the development of the AC drive system. However, as the convertor system applied GTO thyristor as a power device and its switching frequency was relatively low as much as about 400Hz, noise from traction transformers or traction motors generated. To solve this problem, anti-noise materials was applied to the floor of the body with the traction transformers or traction motors. On the other hand, looking through the radical development of power devices, GTO thyristor can be replaced by the large-volumized IGBT.

For the future high-speed trains, comfortability becomes an important function. In addition, for speed improvement and less energy consumption, light weight technology of train will be inevitable.

In this circumstance, new convertor system using large-volumized IGBT has been developed for the following generation of the series 300,"NOZOMI. By using IGBT, switching frequency can be set at 1500Hz. Moreover, as maximum voltage of the IGBT device is limited under 2500V, 3 level control (Neutral point clamp; NPC) method is also applied. These methods contributes to reduce noise from the traction transformer or traction motors dramatically, and also reduce higher harmonics from the traction system. IGBT system simplifies auxiliary circuits, such as snubber circuits, compared to GTO thyristor system, as a result, size, weight, and price of the convertor system can be reduced. As reduction of the higher harmonics realizes low heat-loss design of the traction transformer, total weight of the traction system can be largely reduced.

This IGBT applied convertor system will be applied to the new high-speed train, Series 700. The prototype of the series 700 will begin the running test in Autumn in 1997.

In this paper, experimental results of the IGBT convertor system and composition of the convertor are described. In addition, the method to optimize the switching frequency of the IGBT convertor system, based on FFT analysis of the noise and higher harmonics of the vehicle, is introduced.

2. Outline of the IGBT applied convertor system

Figure 2.1 shows the traction system diagram of the IGBT applied power convertor. This system is composed of 2 group of PWM convertor units and a PWM inverter unit. These power units apply 2500V-1000A IGBT as a main power device. Convertor units and inverter unit are linked with 1900V of

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AC - 25kV, 6OH

- IGBT applied power convertor

Figure2.1: Traction system diagram

DC stage. Table 2.1 shows specifications of electric equipment of the

system.

Table21: Snecifications of electric eauionient

Items Specifications

Traction transformer Primary coil: 25kV

Secondary coil: 885kV

Rated output: 3380kVA

Power convertor

1)Convertor unit NPC single—phase voltage source convertor, x 2 units

Input: 885V, 800A (max. 955A)

Career frequency: 1980Hz

Inverter unit NPG three—phase voltage source Inverter, x 1 unit

Output: 1430V, 620A (max. 880A)

0 to 200Hz

Career frequency: 2000Hz

Power device IGBT, 2500V, 1000A, x2parallel

Control method NPC convertor and inverter control

Traction motor Rated output: 300kL x4 parallel

3. Methods of noise reduction from traction transformer and motors

To utilize high-speed switching characteristics of IGBT, noise from traction trans-

former and traction motors are reduced.

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3.1 Method of noise reduction from traction transformer

Because of using high-frequency PWM modulation and NPC control of the power convertor, magnetstrictive noise from traction transformer is reduced, and frequency of the noise becomes higher. Figure 3.1 shows computer simulation of input of voltage and current waveform of convertor. In this simulation, higher-harmonics and ripple are reduced, as a result, waveform becomes nearly sinusoidal shape.

3.2 Method of noise reduction of traction motors

In addition to high frequency PWM modulation and NPC control, wide range of asynchronous PWM mode is applied to inverter control to reduce noise from traction motors. Figure 3.2 shows pulse mode diagram of the inverter. Because of wide range asynchronous mode, noise in pulse mode change is relieved and noise from traction motors in low to middle speed range is reduced.

0

4. Running test result

To evaluate control charac-teristics, noise level, higher-harmonics, and temperature rise of the new IGBT applied convertor, running test was carried out. In the test run, one out of ten convertor of the series 300 high-speed train was replaced from GTO convertor to the new IGBT convertor.

4.1 Control characteristics test

Figure 4.1 shows an oscillo-gram of the IGBT applied power convertor in running test. Control characteristics indicates successful opera-tion.

Voltage t

wavfoam

Current

wavefoam

Figure3. 1: Simulation of input voltage and current waveform of

convertor

[Hz] Asynchronous PWM mcdc Synchronous FWM ..dc

2030

1500

1000

500

VclociLy

Figure 3.2: Pulse mode diagram

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11 1

r' 1 1

Figure 1 Oscillogram In running 1

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4.2 Noise reduction result

To compare between IGBT convertor and GTO convertor, noise level above traction transformer and traction motors in cabin was measured.

4.2.1 Test result of noise reduction of traction transformer

Table 4.1 shows measured noise level of traction transformer. 1Khz and 2kHz region which is sensitive to hearing characteristic of people, was largely breduced.

TnahI P A 1 MIrpI1 nn i Re M nf trntinn transformer

Frequency range of measured noise 1kHz range 2kHz range 4 H range

[ GTO type (fc:420Hz) 56dB 43dB 29dB

IGBT type (fc:1980F1z) 41dB 34dB 23dB

d ifference (IGBT—GTO) —15dB —9dB —6dB

4.2.2 Test result of noise reduction of traction motor Table 4.2 shOws measured noise level of traction motors. Wide range

asynchronous mode contributed to reduce noise in 0 to 110km/h region.

Ts1shI A 9' Mpinqin, pil noise M of trc.tion motor

Speed range (km/h) in measuring noise 0 to 110 110 to 170 170 to 240

GTO type (fc:-420Hz) 70dB 69dB 72dB

IGBT type (fc:-2kHz) 64dB 67dB 71dB

difference (IGBT—GTO) —6dB —2dB -1dB

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Condition: Powering 12 notch, 270km/h 70 I -

dB(A) J

- - (1) Convcrtorcarcerfrcoueuoj: 420Hz

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- - - - - - - - - t - - O 1 2 3 4 5kHz

70 tdB(A)) Convertor career freq c1980Hz

ir*i------- __s -------

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Fig. 5.1: Comparison of level of measured noise on a traction transformer in different career frequency of convertor.

5. Achievements of the development

Achievements of the development and running test of the new IGBT applied power convertor system is introduced below.

5.1 Effect of higher switching frequency

Higher switching frequency of PWM modulation contributes to modify waveform of input and output of the power convertor, as a result, mag-netstrictive noise and higher har-monics is reduced. Higher switching frequency, however, increases switching loss of the convertor and cooling unit becomes larger. There-fore, choosing suitable switching fre-quency is important to optimize traction systems.

For this purpose, 4 different switch-ing frequencies such as 420Hz, 1020Hz, 1500Hz, and 1980Hz were set in the running test, and the effects in 4 different switching fre-quencies were compared and evalu-ated.

5.1.1 Comparison of effect of noise reduction in different switching frequencies

Figure 5.1 shows comparison of FFT analysis results of measured noise above traction transformer in cabin in different switching frequencies

As a result, 1500Hz of switching frequency is effective to reduce noise in 1Khz to 2Khz range, which is sensitive to hearing characteristics.

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5.1.2 Comparison of effect of higher-harmonics reduction in different switching

frequencies

Figure 5.2 shows comparison of waveform and FFT analysis results of measured

current of primary and secondary coil of traction transformer in different switching

frequencies Accordance with increasing the switching frequency, the level of higher-

harmonics becomes smaller. As a result of higher-harmonics analysis, higher-

harmonics up to 40th is reduced below 10% in case of switching frequency of above

1500Hz.

5.2 Suitable switching frequency in this system

As a result of the running test, 1000Hz to 1500Hz of switching frequency is effective

to reduce noise and higher-harmonics reduction. From the view of switching loss,

lower switching frequency is better choice. In addition , in terms of higher-harmonics

guideline, which controls under 40th of higher-harmonics, above 1260Hz of switching

frequency is effective.

In considering these factors, 1300Hz to 1500Hz of switching frequency is suitable to

the IGBT applied traction system. The next generation high-sped train , series 700

applies 1500Hz for its power convertor.

1) C3000 rl or orr t.cqurrtcy: 42011Z

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Figure 5.2: Comparison of current waveform and higher hannonics indifferent career frequency of convertor

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6. Conclusion

To pursue better quality of high-speed train, JR Central has developed the IGBT applied new power convertor system. As a result of the running tests, effect of noise reduction and higher-harmonics reduction was assured. To utilize these achievement of the tests, JR central develops new high-speed train, series 700. The series 700 adopts IGBT applied efficient and compact traction, system. The prototype of the series 700 will launch in Autumn in 1997, and running test will take place.

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