Euratom TORE SUPRA G. Bosia “Automatic control of ITER-like structures” Venice, 21 – 9 - 2004 Automatic Matching of ITER-like structures Automatic Matching

EuratomTORE SUPRA

G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004

AutomatAutomatic Matching of ITER-like structuresic Matching of ITER-like structures

G. Bosia,

and the CEA ICRF Group

EuratomTORE SUPRA


ITER ICRF system requires hands-off operation

Manual preset of array frequency, phase and power time profiles

With an efficiency > 90%

• Automatic acquisition of perfect match

• Uphold of match against load variations

• Protection of array and transmission lines agaist breakdown

• Fast detection of arcs, extinction, power re-application.

This scenario, is a necessary condition for ICH to be included in ITER auxiliary heating systems

EuratomTORE SUPRA


Effects of coupling in a single ITER-like structure

• The effects of coupling are negligible if the coupling is less than 20 dB. This condition is verified on the

TS ITER prototype.

• Inductive coupling between half sections is one of the several possible sources of electrical asymmetry of the circuit

• Asymmetry makes the half sections currents not complex conjugate (and load resilience is reduced) if the coupling coefficient is high (kp > 1 %) and if one tries to match to a resistive input impedance (R0).

• For any level of coupling, the half sections currents remain complex conjugate and load resilience essentially unaffected if the ILS is matched to

Zin = R0+ i kp X.

kp2 = Xm

2/ X1X2

R X XC1

R X XC2

R0 = 4

R X XC1

R X XC2

R0 = 4 Zin = R0Zin = R0+ i kp

EuratomTORE SUPRA


Effects of coupling on “load resilience”Effects of coupling on “load resilience”

kp =0.00

.

.

kp =0.02

.

kp =0.04

EuratomTORE SUPRA


Array of ITER-like structures

ITER Reference Design 2 x 4 ILS

CEA upgrade proposal 3 x 4 ILS

TS ITER Proto 1 x 2 ILS

EuratomTORE SUPRA


Effects of coupling in a poloidal/toroidal array I)

• Coupling between elements in an array fed by different RF sources has in general no effect on load resilience.

• However, inter-element coupling has important effects on both the location of the match point in the parameter space and on match acquisition if the RF sources introduce electrical asymmetries in the system.

• For cases having practical relevance, the array elements behave as they were independent, if adjacent currents in the array are equal in module and in- or out- of phase

• If not,

• number and location of match points degenerates in a way depending on both load and source (in particular on load power factor)

• matching some element of the array becomes impossible with pure reactances

This behaviour is true for any array with multiple sources

EuratomTORE SUPRA


Effect of poloidal septum on toroidal coupling

20 40 60 800.2

0.1

0

0.1

0.2

Frequency (MHz)

S13

/ S

1 (r

etra

cted

sep

tum

)

20 40 60 800.02

0.01

0

0.01

0.02

Frequency (MHz)

S13

/ S

11 (

full

sept

um)

Retracted septum Full septum

EuratomTORE SUPRA


Effects of coupling in a poloidal/toroidal array II)

kt

0.01

0.023

0.037

0.05

0.1 0.2 0.3 0.4 0.50

20

40

60

80

Load resistance (Rs)

Cri

tical

pha

se a

ngle

kt 0.01kt 0.023

kt 0.037kt 0.005

K = 2.3 %K = 3,7 %

K = 1 %

K = 5 %

Critical angle in ITER Proto (amplitude ratio = 1)

Rs3

Xs1

Va

XC1

Xs3

IaI1

I3

XC3

Rs2

Rs4

Xs2

Vb

Xs4

IbI2

I4

XC4

kp

kp

kt

XC2

Rs1

kt

• At high circuit power factor, for amplitude ratios different from 1 and phasing differing from 0 and by a critical ratio/angle, a parasitic current circulation between RF sources would take place if not prevented by the protection systems

• It becomes impossible to match some array element with pure reactances

Rs3

Xs1

Va

XC1

Xs3

IaI1

I3

XC3

Rs2

Rs4

Xs2

Vb

Xs4

IbI2

I4

XC4

kp

kp

kt

XC2

Rs1

kt

EuratomTORE SUPRA


Recepy for perfect match and load resilience for a single ITER-like structure

Condition 1 implies: 1) a structure geometrically symmetric 2) an active control of the currents in the two half sections

Iin

Z11 I1 XC1

Z22 I2 XC2

Z12, Z21

• Load resilience relies on zeroing of the input reactance by means of phase compensation

1. The currents in the two half sections should be complex conjuate (with Iin as phase reference)

2. The input resistance must be of the same order as the load resistance.

EuratomTORE SUPRA


Recepy for perfect match and load resilience for an array of ITER-like structures

1. The currents in all half sections should be kept complex conjugate (with Iin as phase reference). This implies:1) an array structure geometrically symmetric 2) active control of the currents in the two half sections

2. Each ILS should be kept matched at Zin = R0+ i kp X for maximum load resilience . 3. Currents in adjacent half sections should be kept in- or out- of phase.

I1 I2

I3 I4

EuratomTORE SUPRA


Detection of monitoring, control, and protection signals

Relative detection error :

Control signals Module : < 5%

Phase : < 5 °

BP : DC – 100 Hz

Monitoring signals Module : < 10%

Phase : < 10 °

BP : DC –10 kHz

Protection signals On/Off

BP DC – 1 MHz

To properly operate, a large array needs an integrated control (of frequency, power and phase ) and protection system which relies on the vectorial monitoring of some circuit parameters.

The control system proposed here relies on the vectorial measurement of the input currents in each half section and of the input voltage.

In a next step device, the monitors are exposed to high temperatures and to neutron radiation field. They should therefore be rugged, reasonably insensitive to mechanical, thermal and nuclear loads and not require maintenance and/or recalibration

EuratomTORE SUPRA


Position of the vectorial probe

Impedance probe

The vectorial probe should be ideally located at the T-junction input plane.

However, for impedance matching purposes the currents can be measured anywhere in symmetric position along the sections, provided they are related of the total current rather than to the local current density.

EuratomTORE SUPRA


Sketch of impedance monitor and equivalent circuit

V0 I1 I2

V0

C1

C2

i*k*I1

C2

L

i*k*I2

L

R

RL

V

V1

R

V2

EuratomTORE SUPRA


Circuit equations

I11

kZ C2 V1

V

i

I21

kZ C2 V2

V

i

V0 Vi1 i2

i C1 V

C2

C1V1 V2

Z =R +i (L-1/C2)

R<< L<<1/C2

V1 V i k I1

V2 V i k I2

V0 V 1 2C2

C1

i k I1 I2

i.e. for C1/C2<<1

V V 0C1

C 2

1i k I 1 I 2

EuratomTORE SUPRA


Detection

V1

V2-V

V1-V

V

V2

V1+V2

+

+

+

X

X

Z1

Z2

if 2L C2 << 1 , R << L << 1/ C2 R << L C1<<

C2

Z1 i kC2

C1

V1 V2 V1 V

Z2 i kC2

C1

V1 V2 V2 V

From the basic RF signals V, V1 et V2 all circuit parameters can be computed by simple linear combinations and mixing

EuratomTORE SUPRA


Automatic matching for a single ILS

5. The same matching algorithms used for a single ILS are also used (with additional phase and power control) to match an array of ILS.

1. The proposed automatic matching methods seeks implicit solutions of the match equations.

2. It relies on the operation of two feedback loops operating on the two tuning elements, driven by the error signals constructed as described above . The two loops operate with different time constants, ( FL -> fast loop , SL -> slow loop) so that the FL tracks the SL

3. The module of the input reflection coefficient ΙinΙ, often used for manual match, is not a convenient intelligence for automatic control.

4. Convenient error signals are:

Re(in) and Im(in) = 0 or equivalent for a straight perfect match (if effects of coupling negligible)

Arg(Y1) + Arg(Y2)= 0 and Re(Z0) - R0 =0 for matching to a complex impedance

EuratomTORE SUPRA


Automatic matching for a single ILS: Match trimThis is the case when the settings of the tuning reactances are known at the same frequency but at another load value. This is the case for two similar plasma pulses or for vacuum and plasma.

Plasma load RL =1

M

36

39 C2 (

pF) 42

36 39 C1 (pF) 42

Vacuum match : RL = 0.1

M

36

39 C2 (

pF) 42

36 39 C1 (pF) 42

kp = 0

EuratomTORE SUPRA


Match trim with coupling (kp = 2%)

M

36 39 C1 (pF) 42 36

39 C

2 (pF)

42

M

36 39 C1 (pF) 42 36

39 C

2 (pF)

42

Vacuum match : RL = 0.1 Plasma load RL =1

EuratomTORE SUPRA


Match trim to real input impedance (Zin = R0 : kpXs<< R0)

M M

Im(in) = 0

Re(in) = 0

36 39 C1 (pF) 42 36 39 C1 (pF) 4236

39

C

2 (

pF

)

4

2

36

39

C

2 (

pF

)

4

2

EuratomTORE SUPRA


Matching at Yin = 1/R0 and Yin = 1/(R0-kpX) (kp = 0.02)

m

2 4 6 8 1040

45

50

55

60

0.9

0.85

0.85

0.85

0.8

0.8

0.80.8

0.80.8

0.75

0.75

0.75

0.75

0.75

0.75

0.75

0.75

0.7

0.7

0.7

0.7

0.65

0.65

0.650.65

0.6

0.6

0.6

0.55

0.55

0.55

0.5

0.5

0.5

0.45

0.45

0.4

0.4

0.35

0.35

0.3

0.3

0.25 0.2

0.2

0.150.1

0.1

Arg(Y1) + Arg(Y2)= 0 Re(Z0) = R0

33.8 38.8 C1 (pF) 43.8 33.8 38.8 C1 (pF) 43.8

2.5

2

2

2

2

1.51.5

1.5

1.5

11

1

1

1

0.5

0.50.5

0.5

0.5

0.5

0

0

0.5

0.5

0.5

1

1

1.5

1.5

9

8

7

6

5

5

4

4

3

3

2

2

2

1

1

1

0

0

0

0

1

1

1

1

2

2

2

2

2

3

3 3 3

3

3

33.8

3

8.8

C

2 (p

F)

4

3.8

33.8

3

8.8

C

2 (p

F)

4

3.8

Re(in) = 0 Im(in) = 0

EuratomTORE SUPRA


Matching at Yin =1/(R0-kpX)

m

34 36 38 40 42

34

36

38

40

42

kp = 0.0

m

34 36 38 40 42

34

36

38

40

42

kp =0.04

EuratomTORE SUPRA

G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004 M

Automatic matching for a single ILS: Match acquisition

MY

29 39 C1 (pF) 49

29

3

9

C 2 (p

F)

49

29 39 C1 (pF) 49

29

3

9

C 2 (p

F)

49

To get into the area of the match It is useful to seek for the (unique) series resonance of the defined by the condition Im(Y1) = Im(Y2) = 0 and Im(Vin) = 0 ( Phase Ref: Iin=I1+I2) Series

resonance

• In this case no reactance settings are available at the operating frequency

• The reflection coefficient is not a convenient control variable for match acquisition since the module is flat in most of the parameter space

EuratomTORE SUPRA


Automatic matching for a single ILS: Match acquisition

In this case no reactance settings are available at the operating frequency

M

1) The two capacitors are set at the same value by imposing XC = (XC1-XC2) = 0 by a loop conrolled by

Im (I1) - Im(I2) = 0

Im (I1) - Im(I2) = 0

2) The series resonance is tracked by imposing

XC = (XC1+XC2)/2 = Xs

by a loop controlled by

Im (Iin) – Im(Vin) =0

Im (Iin) – Im(Vin) =0

3) The match point is reached from the series

resonance point as described above

Series resonance

18 38 C1 (pF) 58

18

3

8

C

2 (

pF)

58

EuratomTORE SUPRA


Match acquisition pathMatch acquisition path

010

2030

4050

01020

304050

0.0499

0.18

0.32

0.45

0.59

0.72

0.85

C1

C2

Series resonance point

EuratomTORE SUPRA


Matching an array of ILS• Matching an array of ILS is performed in the same way as for the single ILS.

1. The array elements are sequentially set to the array (single) series resonance at the desired frequency ( the array is mismatched).

2. All elements are powered at equal power and in or out of phase (the array is mismatched)

3. The the match condition to real or complex impedance is applied with similar time constants. Convergence to match is not critical because the array elements are virtually decoupled by the phase/module condition.

4. As for a single ILS, step 1 and 2 are necessary only if no previous settings of the tuning reactances are known at the same frequency but at another load value (like the vacuum match

Match acquisition

Match trim

EuratomTORE SUPRA


Conclusions

• A ITER-like array can be in principle be automatically matched for most foreseable load conditions, and in condition of “load resilience”, by using two capacitive tuning elements and an inductive trim located in the transmission line. .

• To obtain this result, the vectorial control of the currents in each half section of the array, as well as of all input voltage(s) are necessary.

• These can be implemented by an integrated, power, phase and match control system, (which can also provide array protection against voltage breakdown) by a set of 3N control loops, acting on the 2N capacitive elements and N inductive trims, driven by 3 N vectorial measurements.

• This proposal needs an experimental validation and probably some improvement. It is our intention to build this control system and to test it on the Tore Supra ITER Prototype next year.

EuratomTORE SUPRA


Match trim to complex input impedance (Zin = R0 + kpXs)

ReY ImY36 39 C1 (pF) 42 36 39 C1 (pF) 42

36

39

C

2 (

pF

)

4

2

36

39

C

2 (

pF

)

4

2

C

C C

C

Im(Y1)+ Im(Y2) = 0

Re(Y1)+ Re(Y2) = 1/R0

Im(Y1)+ Im(Y2) = 0

Re(Y1)+ Re(Y2) = 1/R0

Documents

Euratom TORE SUPRA G. Bosia “Automatic control of ITER-like structures” Venice, 21 – 9 - 2004 Automatic Matching of ITER-like structures Automatic Matching