euratom tore supra g. bosia “automatic control of iter-like structures” venice, 21 – 9 - 2004...
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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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
Effects of coupling on “load resilience”Effects of coupling on “load resilience”
kp =0.00
.
.
kp =0.02
.
kp =0.04
EuratomTORE SUPRA
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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
G. Bosia “Automatic control of ITER-like structures” Venice , 21 – 9 - 2004
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