Fk. Bordry AB/POAcademic Training - 27th March 2003
Technological Challenges for the LHC
Power converters for the LHCFrédérick BORDRY AB-PO
?I (A)
t
11800
20 min
-10 A/sec
+10 A/sec
2 min
several hours
0.1 A/sec350 A
1 min
350 A
pre-injection (1 min - 1 h)
860 A
860 A
500 W
2,2 MW
115 kW
Fk. Bordry AB/POAcademic Training - 27th March 2003
What’s special about Powering Superconducting Magnets ?What’s special about Powering Superconducting Magnets ?
High Current Large Inductance
No Resistance
Need heavy warm cabling Need to be near to feed point
Difficult and expensive power converter output stage
Large Stored Energy, 1/2 LI2
Need to handle carefully!
Large Time Constant, L/R Boost voltages (high voltage only during the ramps) Difficult control loops
Tendency to quench Need to take special precautions (energy)
Fk. Bordry AB/POAcademic Training - 27th March 2003
• The beams are controlled by:• 1232 SC Main Dipole magnets to bend the beams
• 392 SC Main Quadrupole magnets to focus the beams
• 124 SC Quadrupole / Dipole Insertion magnets (in 196 circuits of ~ 6 kA)
• 6340 SC Corrector magnets (in 1460 circuits 60 to 600A)
• 112 Warm magnets (in 38 circuits 600 to 900A)
• SC RF Cavities to accelerate and stabilize the beam
– All ~8000 magnets need to be powered in a very controlled and precise manner
LHC Large Hadron Collider - What needs powering?LHC Large Hadron Collider - What needs powering?
Fk. Bordry AB/POAcademic Training - 27th March 2003
LHC : 1232 SC Main Dipole magnetsLHC : 1232 SC Main Dipole magnets
One circuit or several circuits ?
Magnet inductance : L = 108 mH
Ltotal=1232 * 0.108 = 133 HRamp: LdI/dt = 1330V
Discharge (quench; 120 A/s): 16kV
Nominal current 11.8 kAStored Energy = 9.3 GJ
Ultimate current = 13kAStored Energy = 11.3 GJ
L/R 50 hours !!!!
Fk. Bordry AB/POAcademic Training - 27th March 2003
Natural segmentation into 8 units as no cryostat in straight sections. Warm cable connections costly in copper , power losses (~30MW) and power
converters Total stored electrical energy in LHC main dipoles is ~10.6 GJ. Discharge in
120 seconds means 16 kV! Only 1/8 of the machine needs to be discharged if one magnet quenches
• No risk of total machine avalanche quench, (false quench detection and provocation)
Earthing of the ring in eight galvanically isolated sectors Less risk of build-up of voltages
• Only two sets of switches for dipoles, one for quads, no timing problems
• Smaller resonant circuit Eight sub-units give easier installation, testing, commissioning and fault
finding for many systems Allows sector-to-sector correction of magnet errors due to different cable,
magnet manufacturers, etc..
Need to track from sector to sector
Why an Electrical Segmentation of the machine?Why an Electrical Segmentation of the machine?
Fk. Bordry AB/POAcademic Training - 27th March 2003
Tracking between the 8 main dipole converters
ppm AccuracyB/Bnom = I/Inom = ppm
B = 9 10-6 = 1.8 10-4 TB/Bo = 15 10-6
Orbit excursion :X = Dx . B/Bo = ~ .035 mmX = .7 mm => = 20 ppm
ppm AccuracyB/Bnom = I/Inom = ppm
B = 9 10-6 = 1.8 10-4 TB/Bo = 15 10-6
Orbit excursion :X = Dx . B/Bo = ~ .035 mmX = .7 mm => = 20 ppm
Could be corrected with a pilot runand new cycle => reproducibility10 ppm reproducibility Orbit excursion :X = Dx . B/Bo = ~ 0.35 mm !!!
”It would be better with 5 ppm”Oliver Brüning
Could be corrected with a pilot runand new cycle => reproducibility10 ppm reproducibility Orbit excursion :X = Dx . B/Bo = ~ 0.35 mm !!!
”It would be better with 5 ppm”Oliver Brüning
Fk. Bordry AB/POAcademic Training - 27th March 2003
Power Converter Tolerances for LHCPower Converter Tolerances for LHC
Precision Control
Inner triplet 8000/ 6000
Unipolar ± 70 ± 20 with calibration
± 10 ± 5 1
Dispersion suppressor 6000 Unipolar ± 70 ± 10 ± 5 15
Insertion quadrupoles 6000 Unipolar ± 70 ± 10 ± 5 15
Separators (D1,D2,D3,D4) 6000 Unipolar ± 70 ± 10 ± 5 15
Trim quadrupoles 600 Bipolar ± 200 ± 50 ± 10 30
SSS correctors 600 Bipolar ± 200 ± 50 ± 10 30
Spool pieces 600 Bipolar ± 200 ± 50 ± 10 30
Orbit correctors 120/60 Bipolar ± 1000 ± 100 ± 50 30
Circuit Nominal Current One Year One day 1/2 hour ResolutionType Current Polarity Accuracy Reproducibility Stability
(A) (ppm of Inominal) (ppm of Inominal) (ppm of Inominal) (ppm of Inominal)
Main Bends, Main Quads 13000 Unipolar ± 50 ± 20 with calibration
± 5 ± 3 1
Fk. Bordry AB/POAcademic Training - 27th March 2003
LHC Power Converters
Number of Converters: 1720Total Current :1860 kA
Steady State Input : 63 MWPeak Input : 86 MW
Number of Converters: 1720Total Current :1860 kA
Steady State Input : 63 MWPeak Input : 86 MW
LEP % LHC
Fk. Bordry AB/POAcademic Training - 27th March 2003
LEP versus LHC for Power ConvertersLEP versus LHC for Power Converters
LEP 200 (up to 110 GeV)Number of converters 900Installed Power = 130 MW (80 MW for the magnets and 50 MW for RF cavities)
Total output current = 115 kAMain dipole current = 4500AMain quadrupole current = 420 A
LHC (up to 7.7 TeV)Number of converters 1720Installed Power = 86 MW (40MW for cryogenics)(70 MW for the magnets and 16 MW for RF cavities)Flat top at 7.7 TeV : 50 MW
Total output current = 1’860 kAMain dipole current = 13’000AMain quadrupole current = 13’000 A
Fk. Bordry AB/POAcademic Training - 27th March 2003
Fk. Bordry AB/POAcademic Training - 27th March 2003
Performances : -High current with high precision (accuracy, reproducibility, stability, resolution) and large dynamics-current range (for 1-quadrant converter: from 1% to 100%)- a lot of 4-quadrant converters (energy from magnets)- tracking : Need to track from sector to sector- voltage ripple and perturbation rejection
The Challenges : The Challenges :
Installation (LEP infrastructure) and Operation: - volume (a lot of converter shall be back-to-back)
- weight (difficult access) => modular approach- radiation for [±60A,±8V] converters- losses extraction : high efficiency, water cooling- EMC : very close to the others equipment ; system approach
Fk. Bordry AB/POAcademic Training - 27th March 2003
UA23 (Ex-LEP Klystron gallery)Now used to house the majority of
machine equipment
such as power converters, magnet protection, injection,
extraction, RF generators, etc.
Very Low Radiation DoseNo Access during “Beam-On”
Access with full power on
Very Low Radiation DoseNo Access during “Beam-On”
Access with full power on
Fk. Bordry AB/POAcademic Training - 27th March 2003
Volume, back-to-back, losses , weight,...No Access during “Beam-On”Access restricted without beam
New Enlargement (RR) for Machine Power Converters around ATLAS and CMS
New Enlargement (RR) for Machine Power Converters around ATLAS and CMS
Constraints :
Fk. Bordry AB/POAcademic Training - 27th March 2003
Radiation Dose1 Gy/year under dipoles
No Access during “Beam-On”Access restricted without beam : Low power
Main Arc TunnelMain Arc Tunnel Orbit Corrector PCs4*[60A,8V]
752 converters
Orbit Corrector PCs4*[60A,8V]
752 converters
High reliability :MTBF : 80 ’000 h1 converter breakdown every 4 daysOne campaign every 2 or 3 months
Fk. Bordry AB/POAcademic Training - 27th March 2003
General approachGeneral approach
• Minimise the number of converter types
• Separate out the subsystems that are desirable/acceptable by industry. Place development and production contracts.
• Design and build prototypes of remaining subsystems. Place production contracts.
• Assume system integration responsibility
• Integration and test at CERN before installation
Fk. Bordry AB/POAcademic Training - 27th March 2003
Special DevelopmentSpecial Development• Converter topologies :
– High current (13kA) and high power (2.5 MW) 2-quadrant converters (main dipoles)
– Switch-mode converters (soft-commutation 20 to 100 kHz)• Parallel subconverters
• 4-quadrant converters (energy management)
• High precision current transducer (DCCT)• Current calibration system• High precision ADC (>20 bits ; )• Control loops :
– robust digital loop (RST)
– Inner triplet powering (nested converters => decoupling)
Fk. Bordry AB/POAcademic Training - 27th March 2003
+15o
-15o3 Phase50 Hz
Supply
Good Symmetry
Freewheelcircuit
- Used for booster of Main Bend and large warm magnets
- Heavy and large- Voltage bandwidth < 70Hz- Well proven- Inversion possible
Two Quadrant Phase Controlled Rectifiers for high current SC magnets:
Power Converter Topologies
Fk. Bordry AB/POAcademic Training - 27th March 2003
[13kA,±190 V]Few ppm
Main dipole power converter
11 m
Dev.
I (A)
t
11800
20 min
-10 A/sec
+10 A/sec
2 min
several hours
0.1 A/sec350 A
1 min
350 A
pre-injection (1 min - 1 h)
860 A
860 A
500 W
2,2 MW
115 kW
Fk. Bordry AB/POAcademic Training - 27th March 2003
Power Diode and Thyristor
or SCR (Silicon-Controlled Rectifier )
Link to frequency of the electrical network
50 Hz (60 Hz)
High frequency => high performances (ripple, bandwidth, perturbation rejection,...)small magnetic (volume, weight)
From mercury arc rectifier, grid-controlled vacuum-tube rectifier, inignitron ,….
High frequency power semiconductors :
MosFet, IGBTs , GTOs, MCTs,….
Fk. Bordry AB/POAcademic Training - 27th March 2003
Low speed
High speed
Large Filtering
Light Filtering
Fk. Bordry AB/POAcademic Training - 27th March 2003
Voltage loop: bandwidth few kHz
AC50 Hz
AC20 - 100 kHz
DC DC
Fast power semiconductors (IGBT)
Semiconductor losses :soft commutation
HF transformer and output filter : ferrite
• light weight, reduced volume (HF transformers and filters)
• good power factor (0.95)
• high bandwidth and good response time
• Soft commutation gives low losses and low electrical noise
• small residual current ripple at output
• light weight, reduced volume (HF transformers and filters)
• good power factor (0.95)
• high bandwidth and good response time
• Soft commutation gives low losses and low electrical noise
• small residual current ripple at output
Switch-Mode Power ConvertersSwitch-Mode Power Converters
+
- +
-
Passive high-currentoutput stage
HF soft-commutation inverteron low current input side
Fk. Bordry AB/POAcademic Training - 27th March 2003
OutputModuleInverter ModuleInput Module Reactive network
+
-
HF soft-commutation inverteron low current input side
Passive high-currentoutput stage
Sub-converter
3.25 kA , 18Vor
2kA , 8V
Inverter : 20 - 50 kHz30 - 70 KVA
Since they are natural current sources, and can be easily paralleled to make up very high currents
Fk. Bordry AB/POAcademic Training - 27th March 2003
Current sources in parallel
13 kA, 16V
3.25 kA , 16 V
3.25 kA , 16 V
3.25 kA , 16 V
3.25 kA , 16 V
3.25 kA , 16 V
• n + 1 subconverters : redundancy, reliability• repairability• ease of handling underground• versatility (6.5kA, 9.75kA, 13kA, 21 kA)
• n + 1 subconverters : redundancy, reliability• repairability• ease of handling underground• versatility (6.5kA, 9.75kA, 13kA, 21 kA)
Fk. Bordry AB/POAcademic Training - 27th March 2003
Loop
Fk. Bordry AB/POAcademic Training - 27th March 2003
Line-commutatedthyristor-controlled converter
SCR semiconductor
Switch Mode Converter
IGBTsemiconductor
[14kA,16V] converterVolume : 25 m3
Weight : 8 tonsRipple : ~ 200 mVVoltage bandwidth : 40 Hz
[16kA,16V] converterVolume : 6 m3
Weight : 1.2 tonsRipple : ~ 10 mVVoltage bandwidth : 1000 Hz
Dev.
Fk. Bordry AB/POAcademic Training - 27th March 2003
Imeasured
V
IIref B
+ Reg.
F(s)-
Vref
V
G(s)
Current loopVoltage loop
Fk. Bordry AB/POAcademic Training - 27th March 2003
1- Fast internal current source FCLB ~ 8 kHz
2- Global voltage loop FCLB ~ 700 Hz
3- High precision current loop (DCCT) FCLB ~ 0.1 - 1 Hz
Control loopsControl loops
Fk. Bordry AB/POAcademic Training - 27th March 2003
Digital current loop : RST algorithmDigital current loop : RST algorithm
FrequencyDivider
T 1/Syref(k)
k.Ts
ADC
Power Party(t)
DAC
Antialiasing
filter k
DigitalFilterR
Ts
Over sampling
Digital controller
Tracking and Regulation with independent objectives
Tracking and Regulation with independent objectives
Tracking Regulation
Fk. Bordry AB/POAcademic Training - 27th March 2003
0
20
40
60
80
0 1 2 3 4 5 6 7 8
0
1
2
3
4
Cu
rren
t of
fset
in M
illi
amp
s
Cur
rent
offs
et in
ppm
of 2
0 kA
Time in Seconds
I0 = 1019.9 Amps
Reference
Measured
Cur
rent
in A
mps
500.0
500.1
500.2
0 1 2 3 4 5 6
0
5
10
Cur
rent
offs
et in
ppm
of 2
0 kA
Time in Seconds
1ppm
Reference
Measured
Fk. Bordry AB/POAcademic Training - 27th March 2003
String 2 Powering area
Fk. Bordry AB/POAcademic Training - 27th March 2003
Power cycle, 13A.s-1, ±600A
Reception
270 mm
Fk. Bordry AB/POAcademic Training - 27th March 2003
1200 1400 1600 1800 2000 2200 2400
200
205
210
215
220
225
Start of the ramp (from 200 A to 225 A)
dI/dt = 50 A/s
1950 2000 2050 2100 2150 2200
210
211
212
213
214
215
Iref
ADC
2060 2070 2080 2090 2100 2110
211.5
211.6
211.7
211.8
211.9
212
212.1
212.2
212.3
212.4
212.5
10 ms
No lagging error !
Fk. Bordry AB/POAcademic Training - 27th March 2003
1000 2000 3000 4000 5000 6000 7000 8000 9000
1.2
1.22
1.24
1.26
1.28
1.3
x 104
[13kA,18V] converter 1mH inductance ; 0.8 m resistance( = 1.5 s)dI/dt = 200 A/s
[13kA,18V] converter 1mH inductance ; 0.8 m resistance( = 1.5 s)dI/dt = 200 A/s
8550 8600 8650 8700 8750 8800 8850 8900 8950 9000
1.2999
1.2999
1.2999
1.3
1.3
1.3
x 104
25 ppm
1 A
8700 8750 8800 8850 8900 8950 9000
1.3
1.3
1.3
1.3
1.3
1.3
1.3
x 104
10 ppm
Ramp from 200 A to 13000A
Fk. Bordry AB/POAcademic Training - 27th March 2003
Integration , system with protection, circuitGetting the current into the coldGetting the current into the cold
Current source Power Converter13kA, 10V flat top, ± 180V boostTime Constant = 23000 seconds (6 hours 23 minutes)
2x Energy extraction systems.Maximum rate of discharge = 120A/sec.
Cryo feedboxes, Current leads,…
Cold cryostat : magnets, bus bars, diodes,… 13kA
Karl Hubert Mess
Fk. Bordry AB/POAcademic Training - 27th March 2003
Fk. Bordry AB/POAcademic Training - 27th March 2003
Four Point Feed of LHCFour Point Feed of LHC
Sector
Continuous Cryostat/Cryoline Superconducting bus-bars runthrough cryostat connecting magnets.Current feeds at extreme ends.
Other central insertion elementseg. Low Betas, separator dipoles
COLD (<2K) 2.9km
WARM500m
1
5
Cryogenic feed
DC Power feed
3
Oct
ant
DC Power
Main Arc FODO cellscontaining; main dipoles andquadrupoles, chromaticity sextupoles, octupoles, tuning and skew quadrupoles, spool pieces,orbit correctors
Matching section of insertioncontaining; dispersion suppressors,matching section, and electricalfeedbox.2
4 6
8
7LHC27 km Circumference
Courtesy of P.Proudlock
Fk. Bordry AB/POAcademic Training - 27th March 2003
One Sector (1/8) of the LHC MachineOne Sector (1/8) of the LHC Machine
Cryostat containing 154 Main Dipoles
Nominal Current = 11.8kA (For 7 TeV)Ultimate Current = 13kA (For 9 Tesla)23x3x2=138 magnets in the arc
16 magnets in the two dispersion suppressors154 magnets in total
Ltotal = 0.108 H x 154 16.6 H(LHC sector 1.2GJ at 11.8kA, 1.4 GJ at 13kA!)(HERA ~ 480 MJ)(Tevatron ~ 300 MJ)Charging voltage= 16.6 Hx10A/sec= ±166V (2.2MW)
0 mins
Time Constant = 23000 seconds (6 hours 23 minutes)
Fk. Bordry AB/POAcademic Training - 27th March 2003
LHC power convertersLHC power converters
A- Elementary module [3.25 kA, 18V], [2kA,8V] : (~120) (~700)
Switch Mode Converter (25-40 kHz, soft commutation)Modular approach : 4.0 kA (28) , 6.0 kA (160) , 8.0 kA (8) , 13 kA (24)Redundancy; small volume and weight
B- Unipolar and Bipolar converters 600A [± 600 A,± 10 V] : (~ 328) ; [600 A,10 V] : (~ 70) [± 600 A,± 40 V] : (~ 40)
Energy dissipation SMPC : soft commutation ; 50-100 kHz
C- Bipolar converter [±60 A, ± 8 V] and [±120A,±10V] (~760) (~300)
SMPC : soft commutation SMPC : soft commutation High reliability, radiation resistance (tunnel installation)
D- High voltage power converter [13 kA, ±180 V] (8) High power SCR converter and Topology studies
Ramp (up and down) : [13 kA, ± 180 V] Flat bottom and flat top : [13 kA, 18 V] SCR converter : [13 kA, ± 180 V] with Active filter : ±600A,±12V
Fk. Bordry AB/POAcademic Training - 27th March 2003
DCCT Performance Requirements
Ratings Budget Stability Reproducibility Accuracy LHC 3 5 50 Class 1
Main Dipoles, Main Quadrupoles, inner triplet
13kA 7kA 6kA
DCCT 1 5 20
LHC 5 10 70 Class 2 Other high current converters
6kA 5kA 4kA DCCT 1 7 25
LHC 10 50 200 Class 3 Multipole correctors
600A
DCCT 3 25 110
LHC 50 100 1000 Class 4 Orbit correctors
60A 120A
DCCT 20 70 300
Fk. Bordry AB/POAcademic Training - 27th March 2003
Class1 DCCTs (13kA)Class1 DCCTs (13kA)
- Highest performance - state of the art- Separate Head and electronics chassis 19” rack mounting.- Fitted with Calibration Windings- Temperature-controlled environment in the Accelerator.- Full testing and calibration at CERN on the 20kA Test Bed.
- Highest performance - state of the art- Separate Head and electronics chassis 19” rack mounting.- Fitted with Calibration Windings- Temperature-controlled environment in the Accelerator.- Full testing and calibration at CERN on the 20kA Test Bed.
Fk. Bordry AB/POAcademic Training - 27th March 2003
4kA to 8kA DCCTs
600A DCCTs
120A DCCTs
Fk. Bordry AB/POAcademic Training - 27th March 2003
Main Dipole Current CycleMain Dipole Current Cycle
I
t
11500 A
20 min
-10 A/sec(~20 mins)
+10 A/sec(~25 mins)
3-5 mins
several hours(~24 hrs)
0.1 A/sec350 A
1 min
350 A
pre-injection(0-1 hr)
740 A
740 A
500 W
2.2 MW
115 kW
InjectionPlateau
Acceleration
CoastDumpBeam
Fk. Bordry AB/POAcademic Training - 27th March 2003
One Sector (1/8) of the LHC MachineOne Sector (1/8) of the LHC Machine
Total inductance = 16.6H. Total stored energy = 1.2GJ
Current source Power Converter13kA, 10V flat top, ± 180V boostTime Constant = 23000 seconds (6 hours 23 minutes)
EVENPOINTS
2x Energy extraction systems.Maximum rate of discharge = 120A/sec.
ODDPOINTS
Cryostat containing 154 Main Dipoles 13kA
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