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Power Electronics No. 15: Three-phase Inverter II

Takeshi Furuhashi Furuhashi_at_cse.nagoya-u.ac.jp

Three Pulse PWM

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If vcomu > vtri 　Tr1 ON，Tr2 OFF If vcomu < vtri 　Tr1 OFF，Tr2 ON

If vcomw > vtri 　Tr5 ON，Tr6 OFF If vcomw < vtri 　Tr5 OFF，Tr6 ON

If vcomv > vtri 　Tr3 ON，Tr4 OFF If vcomv < vtri 　Tr3 OFF，Tr4 ON

-1 -0.5

0.5 1

5 6 6 5 5 6

1 2 1 1 2 2

3 4 4 3 3 4

vcomv vcomw vtri vcomu

vvw

vwu

vuv

0

VE

0

VE

0

VE

0

-VE

VE

0

-VE

VE

0

-VE

VE

vv

vw

vu

t

t

t

t

t

t

t

vuv=vu - vv

Experimental circuit of the three-phase inverter

vtri

vcomv

vPWMu

- - vPWMw -

VE

D6 Tr4 D4 Tr6 Tr2 D2

D1 Tr1 D5 D3

Tr3 Tr5

vPWMv

vcomw

vcomu

+ + +

vw vu vv

vvw vuv

vR

R = 2 [kΩ], L=150 [mH]

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Waveforms of the output voltage and current in the case of a three-pulse PWM fsw = 15[kHz], R=2[kΩ], L150[mH], VE = 6[V]

0.1 0.2 0.3 0.4

-6 -4 -2

2 4 6

0.1 0.2 0.3 0.4

2 4 6

2 4 6

0.1 0.2 0.3 0.4

-1

-0.5

0.5

1

t[ms]

t[ms]

t[ms]

t[ms]

vcomv vtri vcomu

vv

vu

[V]

[V]

vuv

vR

4

0.2 0.4 0.6 0.8 1 2 4 6

0.2 0.4 0.6 0.8 1

2 4 6

0.2 0.4 0.6 0.8 1

-1

-0.5

0.5

1

t[ms]

t[ms]

t[ms]

t[ms]

vcomv vcomu

vv

vuv

vu

[V]

[V]

vR

0.2 0.4 0.6 0.8 1

-6 -4 -2

2 4 6

vtri

Waveforms of the output voltage and current in the case of a nine-pulse PWM fsw = 15[kHz], R=2[kΩ], L150[mH], VE = 6[V]

6

0.5 1 1.5 2 2.5 3 3.5

-1

-0.5

0.5

1

0.5 1 1.5 2 2.5 3 3.5

-6

-4

-2

2

4

6

vcomu

vuv

vtri

vR

t[ms]

t[ms]

Waveforms of the output voltage and current in the case of a 27-pulse PWM fsw = 15[kHz], R=2[kΩ], L150[mH], VE = 6[V]

0.005 0.01 0.015 0.02

-1

-0.5

0.5

1

0.005 0.01 0.015 0.02

-1

-0.5

0.5

1

vtri vcomu

vuv

vtri vcomu

vuv

(b) 9-pulse (a) 3-pulse

FFT analysis of line-to-line voltages

0.005 0.01 0.015 0.02

-1

1

0.005 0.01 0.015 0.02

-1

1

Fundamental component

7-th harmonic component 11-th

17-th

19-th

Fundamental component

7-th harmonic component 11-th

19-th

17-th

0.2

0.4

0.6

0.8

1

0.2

0.4

0.6

0.8

1

23-th

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Asynchronous mode

vuv

vtri vcomu

t

vtri vcomu

vuv

vtri vcomu

vuv

t

t

t

t

t

Zero crossing points of the command voltage and triangular voltage do not coincide.

Freq of the command voltage is varying.

Freq of the triangular voltage is constant.

Switching frequency is constant.

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-1

1

-VE

VE

-1

1

-VE

VE

-1

1

-VE

VE

vuv

vtri vcomu

vtri vcomu

vuv

vtri vcomu

vuv

vcomu

fcom / ftri = 1/9

Increased frequency of voltage command Increased switching frequency

Synchronous mode Zero crossing points of the command voltage and triangular voltage always coincide.

Tr 2SC4507 400V, 5A

vCE

iC

D RL 100[Ω]

vBE

RB 100 [Ω]

VE 100 [V]

iC

0

50

100

150

0.5 1 1.5 2

-10 -5

0

5

10

15

0

t [µs]

t [µs]

vCE

vBE

[A]

vCE vBE [V]

0

0.5

1

0.5 1 1.5 2

Switching loss by transistor (example of an experimental waveform）

Energy loss Eloss occurs while vCE > 0 and iC > 0.

[J] dtivE CCEloss ∫=

Collector current iC keeps flowing even though the voltage between the base and emitter vBE is made negative.

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-1

1

-VE

VE

-1

1

-VE

VE

-1

1

-VE

VE

fcom / ftri = 1/9 (constant)

Synchronous mode

-VE

VE

Increase of fsw

→ Increase of power loss

　 Ploss = Eloss ×fsw [W]

→ Upper limit of fsw

Ex. Shinkansen train

700-Series (1.5kHz) fcom / ftri = 1/3 (constant)

fcom / ftri = 1 (constant)

(b) 3-pulse PWM

(a) 9-pulse PWM

(c) 120 degree conduction mode

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Speed of the Shinkansen train

Switc

hing

freq

uenc

y

3P 1P

9P

Example of switching between asynchronous mode and synchronous mode

fcom / ftri =1/1 fcom / ftri =1/3 fcom / ftri =1/9

Asynchronous mode Synchronous mode

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-1

1

-VE

VE

-1

1

-VE

VE

(b) 3-pulse PWM

(a) 9-pulse PWM

Asynchronous mode

Speed

Switc

hing

freq

uncy

Synchronous mode

3P

1P

9P -1

1

-VE

VE

Zero crossing points of the voltage command and triangular waveform always coincide.

Synchronous mode at high speed

-VE

VE

(c) 120 degree conduction mode

fcom / ftri = 1/9 (constant)

fcom / ftri = 1/3 (constant)

fcom / ftri = 1 (constant)

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If not synchronized!

Asymmetry between positive side and negative side． Waveform varies at every cycle.

Over heating, vibration of motor noisy motor sound

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300-series (（1990～） Max speed: 285 km/h Main motor: Three phase induction motor Power converter: VVVF Inverter (GTO Thyristor) Switching frequency 420 [Hz] Braking method: Regenerative braking The induction motor’s output power is 130% and its weight is half of that of the DC motor. Regenerative braking was first introduced to Shinkansen trains.

100-series（1985～） Max speed: 275 km/h Main motor: DC series wound motor Power converter: Thyristor type Braking method: Resistance braking

Shinkansen

http://ja.wikipedia.org/wiki/新幹線300系電車 http://ja.wikipedia.org/wiki/新幹線100系電車

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500-series（1992～） Max speed: 365km/h Main motor: Three phase induction motor Power converter: VVVF Inverter (GTO Thyristor) Braking method: Regenerative braking

N700-series(2005～) Main motor: Three phase induction motor Power converter: VVVF Inverter (IGBT) Switching frequency: 1.5 [kHz] Braking method: Regenerative braking

・Asynchronous mode 　From the time train leaves a station 　300-series approx. 5 sec 　500-series approx. 22 sec 　N700-series approx. 25 sec ・Sound noise level Sound noise from the motors of N700-series is less than from previous types of Shinkansen trains.

http://ja.wikipedia.org/wiki/新幹線500系電車 http://ja.wikipedia.org/wiki/新幹線N700系電車